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|how lymphoma affects me|
Lymphoma is a tumor of one type of white blood cells that is an important part of your cat’s immune system. The purpose of that cell, the lymphocyte, is to defend your cat’s body from invaders. As a sentinel and soldier of your cat’s defensive system, lymphocytes need a natural capacity to increase their numbers rapidly. But when changes (mutations) occur in their DNA program, their increase in numbers has nothing to do with defending the cat’s body. At that point, the lymphocytes have become a loosely organized tumor, a cancer that has forgotten its original purpose, a lymphoma. This tumor is one of the most common forms of cancer in cats. And cats suffer from it more than any other animal. (ref) It can form in any area of your cat’s body that harbor large numbers of lymphocytes and for a number of different reasons. Those reasons, and the locations the tumor resides have shifted over the last twenty years. Currently, your cat’s digestive system (alimentary system) is the most common target of the problem. That is because the digestive system is home to the largest population of lymphocytes in your cat’s body and, perhaps, because those cells are under constant stimulation by the compounds and organisms passing through the cat’s digestive system.
The frequency of lymphoma in cats and the characteristics of the tumor appear to differ somewhat depending on the area of the World where they are measured. It is hard to explain those moderate differences. Perhaps cat populations and care differ somewhat in different continents, perhaps research studies, techniques and interpretation differ in different environments. Whatever the reason, in the United States today, lymphoma is the most common gastro-intestinal tumor of cats and form about 20% of all tumors discovered in cats . Being a Siamese cat, a shorthaired cat, a male cat or a cat from a cigarette-smoking household appear to increase the chance of this disease slightly. Cats over 7 years of age are at considerably more risk of developing the disease. When the cat’s digestive system is affected, about two-thirds of the time, these lymphomas form in the cat’s small intestine. You can read more about some of these statistics here , and here .
You can read about some general characteristics
of lymphocytes here.
If you read it, you will learn that there are two populations of lymphocytes that can give rise to a lymphoma tumor, T-cells and B-cells. It is not an academic point, because tumors that originate with one type, often behave differently than tumors that originate with the other. The vast majority of these cells in the walls of the cats small intestine are the T-cell type (CD3) .
Over the last 20 years, lymphoma has become a rather common disease - primarily of older cats. The intestines are a common site of the problem and fewer cases can now be attributed to infection with the feline leukemia virus (FLV) or the feline immunodeficiency virus (FIV,= feline AIDS). Good vaccines to prevent FLV and FIV explain much of that shift. Improved awareness, attentive veterinary care and better diagnostic methods might explain some of the rest. But in cats, intestinal lymphoma is often the result of chronic digestive tract inflammation and that has been on the rise as well. (ref) Although lifestyle is important in the development of all cancers, your cat's unique genetic makeup is probably quite important as well. I do not know of studies in cats that examined this, but in dogs, defects in specific genes have been found that favor the development of lymphoma. (ref1,ref2)
Yes.And the way they are classified and named can be terribly confusing. The same problem occurs when lymphomas occur in humans. The World Health Organization attempted to bring some order to naming the types of lymphomas. (ref)
When lymphomas occur in cats under the age of 7, they are most often associated with the feline leukemia virus or the feline immunodeficiency virus. Both these virus greatly increase the tendency for the cat’s lymphocytes to mutate and become cancerous. Since both these virus are generally detected in a cat’s youth, they are a significant cause of lymphoma in younger cats. When the tumor develops due to the influence of these viruses, the lymphomas produced often occur in multiple locations outside of the digestive tract (lymph nodes, chest, etc.).
As feline leukemia becomes less common in cats due to vaccination and in-office testing, the prevalence of lymphoma in young cats has decreased. There was some speculation among veterinarians that lingering feline leukemia virus fragments (= provirus DNA, latent FLV, FeLV-A/B recombinants) in cats that overcame FLV and tested negative on in-office tests might still be at a higher risk of developing lymphoma. Most studies have not found that to be true. You can read some of those studies here , here , here and here
When the virus of FIV is involved in lymphoma, it is usually the cat’s B lymphocytes that become cancerous. You can read more about that situation here.
This has been the traditional way veterinary pathologists classify lymphomas. It is important because how successful treatment in your cat is likely to be is very dependent on the characteristics of the lymphocytes involved. The smaller and closer these cancerous lymphocytes are to normal lymphocytes, the more likely it is that treatment will be successful. The limitations of this method is that, much like a baseball umpire, it can be somewhat subjective depending on the veterinary pathologist making the call and the specimen of tumor with which he/she has been provided.
This is the most treatable form of lymphoma in cats. Pathologists generally compare the diameters of the cancerous lymphocytes to the diameters of the cats red blood cells seen in the same slide. However, it can sometimes be difficult to decide if these cancerous cells would be better called intermediate size lymphocytes - cells a bit less likely to respond well to the medications veterinarians have available. You can read about this form of lymphoma in cats here. It can also be quite difficult for the pathologist to determine if abnormal numbers of lymphocytes represent a true tumor or are normal lymphocytes that are simply there in response to chronic inflammation.
In general, larger lymphocyte size is an indication that the cat’s outlook is poorer. Lymphomas that occur very high in the intestine or stomach and those that occur in the large intestine have a tendency to be this type. They also have a greater tendency to penetrate into the deeper layers of the intestine and the surrounding lymph nodes. You can read a bit about large-cell lymphomas here.
When a major instigator of feline lymphomas was the feline leukemia and the feline aids viruses, the lymphomas tended to spring up in multiple locations outside of the digestive tract (multi-centric). They still do, but not in the quantity that they once did. They now tend to occur in the cat’s digestive (alimentary) tract and the organs that adjoin it (pancreas, liver and gall bladder) - particularly in older cats. Many of the lymphomas that occur in the alimentary tract are quite treatable. You can read more about these tumors and their treatment here , here and here .
Lymphomas have the potential to form in any tissue
that contains a large number of lymphocytes – either naturally or
due to chronic inflammation. This includes the area surrounding the cats
heart (mediastinum) (ref)
, lungs (ref) ,
Gall bladder (ref) , nervous system (ref)
, and lymph nodes. Some associate infection with a bacteria, helicobacter,
as predisposing cats to lymphoma of the stomach. (ref)
There have been cases when the tumor formed in bone (ref) or even the skin (ref) or was involved in a more general leukemia. (ref)
The physical signs that one sees in cats suffering from lymphoma could be the same in many, non-cancerous and cancerous disease that cats develop. Only a pathological examination of tissue samples (biopsies) taken from suspicious areas can determine if the cat suffers from lymphoma. Even that examination is not always clear-cut. That is because common disease of cats that cause chronic inflammation produced clusters of lymphocytes that could be confused with lymphoma. The most common confusion surrounds triad disease of cats which you can read about here. triad.htm Veterinary pathologists have made great efforts to find ways to tell the difference between lymphocytes present because of chronic inflammation and those that are present in a cancerous accumulation. You can read some of the studies that pertain to that problem here , here and here. In late 2015, the Winn Feline Foundation, recognizing how hard lymphoma and IBD are to tell apart, provided a modest grant in the hope of developing a blood test that might help your veterinarian tell the difference. (ref)
Those signs are quite variable. Transformation of lymphocytes into a discrete or diffuse tumor is a gradual process. Early in that process you will notice little to no effect on your cat. Even veterinary exams and test results other than tissue biopsies often offer no clues that the cat is ill.
The other determining factor is what area of your cat’s body harbors the tumor. Whatever the area, the first signs you will usually notice are interruption of normal function, abnormal breathing – should the lymphoma be in the chest, nervous function-should it affect the brain or spine, liver or kidney function – should those organs harbor the tumor and painless swellings when lymph nodes are involved. When lymphoma affects your cat’s digestive system, the first signs seen are usually poor appetite and weight loss, followed later by vomiting or diarrhea. In other cats, an unkempt hair coat and lack of energy and interest may be the only initial signs.
The vagueness of early signs of lymphoma are why most cats are initially treated just for symptoms in the hope that whatever the underlying problem, it will heal with time. It is only when these symptoms persist over months that veterinarians begin to consider more serious problems – like lymphoma.
With time, your veterinarian may detect lumps (swollen lymph nodes) as he/she palpates your cat’s body. With time, the vet may notice intestines thicker and more rigid than they should be when the intestine is the site of the tumor. As lymphoma progresses, many cats become moderately anemic. You can follow Nick, a 10-year old cat, through his diagnostic journey here.
As I mentioned earlier, physical exams in early lymphoma cases are often normal, and physical exams that note weight loss and an unkempt appearance often give no indication of the underlying cause. When an abnormal lump, organ shape, or mass is detected, the vet is well along toward a diagnosis but palpation of the abdomens of cats even in advanced stages of lymphoma can appear completely normal.
No blood test that veterinarians currently have can definitively diagnose lymphoma tumors unless the tumor is of lymphocytes circulating with the blood system itself (a leukemia).
However, complete blood cell counts (CBC/WBCs) sometimes show a mild to moderate anemia (nonregenerative anemia). Even more common is low blood albumin levels (hypoalbuminema). Low blood albumin protein in lymphomas occurs when cats do not eat sufficiently, when there are changes in their intestinal lining that limit their ability to absorb protein (malassimilation) and when changes caused by intestinal lymphomas cause their intestines to leak protein from their circulation. Some of these cats have elevated serum globulin antibodies as well.
Blood cobalamin (vitamin B-12) and folate levels are often reduced in these cats due to decreased intestinal absorption of these nutrients. Occasional cats have higher than normal numbers of lymphocytes circulating in their blood (lymphocytosis). (ref)
Because veterinarians know that cats that are positive for feline leukemia or feline AIDs are at a higher risk for lymphoma, your veterinarian will want to determine their status. You can read about that test as it is commonly performed here.
Lymphoma cannot be diagnosed through conventional x-rays. However, your veterinarian may wish to rule out other possible causes for your pet’s poor health, and x-rays assist in doing that. Occasionally signs of enlarged mesenteric lymph nodes (ref), thickened or dilated loops of intestine and a blurring of abdominal image detail will bring lymphoma to mind – as will increased mass present between your cat’s lungs when its chest is the site of the problem (mediastinal masses).
An ultrasound examination, performed by a veterinary radiologist, will tell your vet more. Evidence that the walls of your cat’s intestines or stomach have thickened, enlarged lymph nodes, and a loss of normal intestinal layers and a narrowed intestinal internal diameter are all compatible with lymphoma or a chronic inflammatory condition such as IBD. You can read how attempts are made to tell them apart here. Ultrasound availability is also invaluable in guiding a needle through the cat’s abdominal wall and into suspected lesions to withdraw cell samples for analysis (fine needle aspiration, cytology and sample histopathology). When performed periodically, ultrasound is also quite helpful in determining if the medications being administered are shrinking the cat’s lymphoma.
Endoscopes are optical apparatus that allow your veterinarian to peer into your cats digestive tract. Veterinary endoscopes are similar, but narrower in diameter to those used in human colonoscopy. Your veterinarian will be looking for abnormally thickened areas in the stomach and intestinal wall, abnormal coloration and, perhaps, ulceration of the intestinal lining. These scopes are designed with a retrieval channel (tube) that allows small snippets of tissue (biopsies) to be harvested and withdrawn whenever the veterinarian encounters a suspicious area. To fully examine the intestinal tract, common endoscopes must be inserted both down the mouth and up the cat’s anus.
Although it is uncommon to use Magnetic resonance imaging in typical lymphoma diagnosis; MRI’s can provide important information when lymphomas occur in unusual locations. You can read about one situation like that here.
As with MRIs, CAT scans are seldom necessary in diagnosing lymphoma. But they can be helpful in judging treatment progress. You can read about a case in which CT scans was helpful here.
Having a veterinary pathologist examine tissue
from a site suspected of harboring a lymphoma is the key method veterinarians
rely upon to diagnose lymphoma. There are many ways that pathologists
decide when cells are cancerous. Cancerous cells tend to be in the process
of division more frequently than they should, they tend to be larger than
the normal cells from which they originated, they tend to loose the distinctive
shape (morphology) of the cells from which they originated, appear where they do not belong and they acquire different color staining characteristics. You can see that all these changes are quite subjective and subject to interpretation. So two pathologists - like two contest judges - are unlikely to make exactly the same call every time. What one hopes for is that there is reasonable agreement. You can read how one Australian group of pathologists attempts to do so here.
Because it can be impossible for pathologists
to decide with certainty if a group (nest)
of lymphocytes constitute a cancerous lymphoma tumor (a
neoplastic population of lymphocytes) or are simply there
to respond to chronic inflammation (a reactive population
of lymphocytes), veterinarians have found techniques that
analyze the composition of the lymphocytes to give them additional clues.
This is particularly helpful when lymphoma is suspected in the cat’s
digestive tract. These techniques also allow veterinarians to determine
if the lymphoma originated from the cat’s T-lymphocytes or B-lymphocytes
– something that can be helpful in devising the best treatment plan.
We know that cancerous lymphocytes tend to arise
from a single defective cell. One, that, like the broom in Disney’s
Sorcerer’s Apprentice, has become oblivious to its environment.
That means that all later generations (a clone) of that cell share the same gene rearrangement. Veterinarians now have tests that can determine if that is the case. When it is found that all the lymphocytes are from a single clone, it is further evidence that a lymphoma is present.
You can read how those tests are used here , here and here.
Yes, it is very important. When tissue samples are collected using the aid
of an endoscopic tube inserted through the cat’s digestive tract
the cat needs no surgery and no more than light anesthesia to perform
the procedure. That is a great plus. The drawback is that samples obtained
that way sample only the most inner layers of the cat’s intestinal
wall. That makes differentiation between chronic inflammatory changes
like IBR and Triad Disease and true lymphoma more difficult. That is because
one gauge of malignancy (cancerous nature)
is the extent to which cells have invaded deeper or surrounding tissues.
These same drawbacks occur when specimens are obtained through a long
ultrasound-guided needle. When actual surgery is performed to harvest samples,
tinny full-thickness specimens can be harvested. Those specimens can often
tell the pathologist things that endoscopically-harvested samples cannot.
Such surgery also offers your veterinarian the best view of what is actually
happening within your cat, what other organs are affected, potential blockages,
etc. The drawback is the stress and risk of general surgery in a cat that
may already be weakened.
So how to obtain biopsy samples is something you and your veterinarian need to discuss together. You can read more about these tradeoffs here and here.
Your cat is truly fortunate if pathologists inform
your veterinarian that the diagnosis is small-cell lymphoma. That form
of lymphoma is the most treatable of all.
That is because the less a cancerous cell has departed from its original makeup, the more it is controllable by drugs that are similar to the hormones that control its cell type before it became cancerous. In this case, non-cancerous lymphocytes are decreased in number by cortisone produced in your cat’s adrenal glands and lymphocytes that have mutated in a cancerous small-cell lymphoma decrease in number when exposed to prednisolone – a synthetic steroid similar to cortisone. When that drug is combined with a second oral drug, chlorambucil, that accomplishes the same thing through a different pathway, most cats show dramatic improvement. That positive response often persists for a number of years. The greater and more dramatic the improvement in the month or so after the drugs are first given, the longer that improvement is likely to last. You can read how those drugs are used and the type of results often obtained here and here.
I included links to studies on the used of chemotherapy drugs for cats with lymphoma. They all report impressively positive results. Please remember that
these studies were on a limited number of cats and that they were done without the controls of hard medical research. These type of studies tend to be moderately biased toward positive results – in this case, the added life span your treated cat might realistically hope to attain. That phenomenon is something akin to one called "publication bias". You can read about that here.
There are a number of accepted treatment plans for these more-malignant lymphomas. However, all those plans include the use of a combination of drugs that have the potential to cause severe side effects and the additional time your cat might realistically gain on this Earth will be quite shorter (60-200 days) than when battling the small-cell forms.
Veterinary oncologists commonly use a combination
of cyclophosphamide, vincristine and prednisolone (COP) or a combination
of cyclophosphamide, doxorubicin , vincristine and prednisolone (CHOP)
to treat cats with the more aggressive large-cell lymphomas.
You can read about those protocols here . Although many of these drugs are given intravenously in the Netherlands they are occasionally given by less stressful routs. (ref)
Other veterinary oncologists prefer what is known as the Madison protocol. This treatment plan combines intermittent (pulsed) use of vincristine, L-Asparaginase, prednisone, cyclophosphamide and Doxorubicin. The median survival time for cats undergoing this procedure is about 210 days although a few isolated cats survive much longer. You can read how this protocol is performed here.
A modified method switches prednisolone for prednisone and throws in methotrexate. (ref)
When radiation is used to treat lymphoma in cats, it is usually as a “rescue” protocol when other techniques no longer keep the lymphoma under control. It does have its place in treating lymphomas that occur in isolated areas of the body susceptible to a focused radiation beam. You can read some articles that explain its use in lymphoma treatment in cats here and here I never recommend it as an option for my clients but I do mention it and some do go that rout. Rescue therapies and last-ditch efforts to keep the cat alive that are not based on radiation also exist. You can read about one here ;but I am philosophically opposed to extending these cat’s suffering.
Surgery is an option for very isolated, well-demarcated (circumscribed) lymphomas – primarily those present in a single isolated lymph node or a single well-defined tumor that is blocking the cat’s intestine. But surgery is usually ineffective in treating the diffuse lymphomas as they usually occur in the cat’s digestive system. When used, surgery in those other cases tended to actually shorten the cat’s remaining life.
It can be difficult to convince a cat to do what you think is in its best interest. Cats are independent creatures that do not willingly make changes in their basic lifestyles.
When a cat is feeling poorly, its relationship with other cats and other pets in the household will change. Most ill cats seem to do better when you define special spaces for them. Keep them in visual or sound contact with the family members – but give them defined areas they have to themselves.
Here are some hints and suggestions :.
Pick an area with impervious floors that are easily washed and sanitized. Pick an area that is airy but not drafty. Hang a thermometer in the room and keep the temperature in the mid to high seventies. Set up a card table on which to keep medications and supplies that need no refrigeration. You will need an accessible sink - preferably one not used for food preparation or frequented by other family members. Make the area inaccessible to unaccompanied small children.
Keep the cat’s food and water close by. Do not expect them to share those facilities with other household cats. Add multiple water sources and feed them smaller portions more frequently than you once did. Consider dog-size water bowels.
Provide multiple, larger litter boxes with lower sides and use a brand of litter less likely to cling to the cat. Be sure it is a dust-free product.
Give your cat help with grooming. Use as soft a slicker brush as one can find at a pet megastore or online. Gently was soiled areas with warm water, a sponge and a very mild non-medicinal soap. Avoid scented products. Carefully clip away the hair surrounding its anus or have a pet groomer do that for you. Cats that produce persistently loose stools often have overly enlarged anal sacs that are both uncomfortable and odorous. Have your vet show you how to massage them empty. Then fully wash that area gently. Pat cats dry with soft paper towels and finish the process with a hair dryer. Always keep your hand in the line of hot air to monitor and not overheat the cat.
Find ways to administer medications with the least stress on the owner and the cat. Have your vet or groomer cut its nails shorter and file the ends of each nail very smooth. If your cat resists its medications, consider purchasing a zippered cat bag or wrap your cat snuggly in a beach towel when you mediate it. Tend to any hand cuts or punctures you may receive in the process immediately. Wash your hands thoroughly after giving medications. Cats usually resist pilling. Ask the vet tech or a more experienced friend to instruct you on how to best give pills. Ask your vet if the medications come in a liquid form or one that can be applied topically or compounded by a specialty pharmacy in other flavors and concentration or if similar medications exist that can be given less frequently or by injection. Keep good track of remaining medication supplies so as not to run out of medication on the weekends.
Begin a diary or daily log in which you record the cat’s weight, body temperature, respiratory rate medication dose and frequency and general condition and symptoms day by day. Include in it the vets phone numbers, the vets off-hour contact number and the number and location of your nearest 24-hour pet emergency clinics.
Cats that are not moving about and that have lost considerable weight, develop ulcers (bed sores) on pressure point or continuously damp or licked areas. Treat them as you would treat bedsores in human family members. The areas where these cats lay need to be extra soft, padded and quite dry. Use washable materials or plan on discarding them frequently.
Be very cautious about using heating pads and heat lamps. I have seen more harm caused by them than good. When your cat requires supplemental heat, consider a hot water bottle or a low-temperature, washable heading pad designed specifically for pets.
Cats that are feeling poorly are very subject to dehydration, both because they tend to drink less and because they loose fluids through diarrhea and vomiting. They will go down hill rapidly when this happens. Have your vet show you the common signs of dehydration you might see (clay-like, inelastic skin, sunken eyes, dry mouth, etc.) and give the cat oral supplemental fluids when this occurs. In severe problems, the cat may need injectable fluids. Ask you vet if this might be the case and if those fluids could be given at home.
Inform your vet of any changes – be they good or worrisome.
to your cat frequently.
Link up, in person or online, with cat owners in the same position as you.
Cancer affect the appetite of cats more than it
does dogs. I do not know why that is, but cats with lymphoma often have
a poor appetite. The best sign that your cat is dealing well with its
problem is its ability to maintain its body weight. Purchase an accurate
table-top digital scale to monitor that. With time, you will probably
have to tempt your cat with savory foods that have the odors and mouth-feel
that your cat most prefers. Commercial prescription diet producers do
a miserable job in providing foods that do that and veterinarians are
drilled by those companies every day not to suggest you make your cat’s
meals at home.
My golden rule is that a cat that eats anything is better off than a cat that eats nothing.
foods make them smell more appetizing.
Foods with pungent odors (meats) are likely to be eaten when commercial cat foods are rejected.
Avoid offering foods that contain preservatives, coloring agents and nitrates.
Offer multiple small feedings
You can sometimes blend foods into a paste or liquid that cats will lap or lap off of their forelegs when they have no interest in eating them otherwise.
Just the fact of cooking these foods in your home fills the house with aromas that stimulate cats to eat.
Stroke your cat to encourage it to eat.
Organ meats are sometimes accepted when red meats are not.
Talk to your cat
There may come a point when you will need to rely on assisted feeding, feeding tubes and appetite stimulants to get your cat the nutrients it requires. Squeeze mustard bottles or turkey basters work well to deliver food into your cat’s mouth. Never elevate the cats head too high when attempting to feed it. You can read about preparing your cat’s diet at home here and an excellent article on the nutritional needs of sick cats here.
The most frustrating problem owners of cats with lymphoma face are the cat’s reluctance to eat. I hope I have given you some ideas that will help you in dealing with that. The second most frustrating problem for owners of cats with intestinal tract lymphoma is soiling the house and a reluctance to use the litter box. Add several more, easy-entry boxed in scattered locations. Experiment with different brands of litter.
Dehydration, due to vomiting, diarrhea and a refusal to drink will need your immediate attention when they occur. Talk with your vet on how best to manage those problems. Take on as much of those duties yourself to avoid stressful trips to the veterinary hospital. Vets differ in their willingness to instruct you in home nursing care. Make it clear to the veterinarian that you are willing and committed to assume those responsibilities.
When lymphoma affects the intestine, blockages sometimes occur. Those need to be deal with promptly by your veterinarian. Their occurrence can sometimes be minimized by altering your cats diet as well as the amount of fiber and water-drawing ingredients (lactulose, polyethylene glycol, etc. ) it contains.
When lymphoma affects organs and areas outside of the digestive tract, it will eventually interfere with the proper function of those organs. Those problems are too numerous for me to list, but your veterinarian will devise strategies to maintain organ function as long as possible.
Your cat’s ability to maintain or gain weight
is the most accurate way of judging your cats progress in fighting lymphoma.
A second key point is that your cat’s long-term prognosis (outlook)
is very dependent on its improvements during the first few weeks of chemotherapy.
The cats that make the most noticeable and dramatic improvements in general
health are also the ones that tend to benefit long term.
You can read how intimately body weight and success are tied together here.
Veterinarians have few object ways of telling you that. We do know that cats on the young end of the age scale when the tumor is first discovered tend to live longer. It also appears that cats that develop T-cell lymphoma types also seem to have a more favorable outlook – although all do not agree on that point.The size of the individual lymphoma cells (small-cell type vs. large-cell or high-grade type) greatly affects survivability. Whereas about 69% of cats with the small-cell types survive an additional 17 month after initiating treatment, only 18% of the more malignant large-cell types live an additional 2.7 months after beginning treatment. The degree with which the lymphoma has penetrated adjoining tissue layers and organs (infiltrative) is also a major factor in survival, as is metastasis of the tumor to other body sites. Vets have also noticed that the severity of weight loss and general condition when therapy is first begun greatly affects its future longevity. The more the cat weight has decreased from its traditional body weight, the less likely therapy is to gain the cat extensive additional time. Nothing is set in stone. There will always be cats and people who defy the odds when struggling with lymphoma. You might take heart in reading about one woman’s remarkable experiences here.
Lymphomas are not, in themselves, painful. But they can affect structures adjacent to them in painful ways. There are many medications to help deal with that. My preference are for fentanyl patches. (these patches can cause constipation which is a manageable problem in some cats and a welcome one in others ref )
When lymphoma affects the digestive tract, it can cause blockages that are painful (colic). That will need to be addressed by your veterinarian. You can read about that problem here. You can read about pain control in cats in general here.
Most cats tell their owners that themselves. You know your cat. Do not let anyone else tell you it is time, or it is not time to let go. Do not let anyone lay guilt at your feet for doing or not doing what they suggest. If you have read this far, you know that veterinarians cannot really predict the outcomes of any therapies they suggest. Specialists tend to paint a rosier picture than veterinarians in general practice. When questionnaires were given to the owners of cats with lymphoma six month after deciding to treat or euthanize their pets, those that were most comfortable with their decision were the ones that had the most caring, empathetic vets who gave them realistic an complete information on their cats outlook that included cost, number of return visits, adverse treatment reactions and realistic possible lifespan. You can read that study here (I linked to it earlier) and another here. You can read some of my thoughts on dealing with the grief that will bring, here.