Plasmacytoma and Myelomas in Dogs

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Plasmacytoma with Multiple myelomas

Question: Recently, I read your response in on of the questions concerning plasmacytoma on a german shephard. You mentioned that there is a slight link between multiple myeloma and plasmacytomas. Recently our Golden Retriever was diagnosed with multiple myeloma( in March) and then in July she started getting plasmacytomas on her body. (One by her neck, a few on her tail and on her legs) You had said that most plasmacytomas of the skin are benign. Her quality of life seems excellent right now. She does not seem bothered by any of it. She is currently on 3mg. of Melphalen and 30mg of Prednisone daily. Any information you have on this would be very helpful. Thanks so much. ( I am a member of your vet info. service. Thanks again.

Mary- I am going to try to reply to all of your emails with this one note. I am sorry for the delay in responding to this question. For some reason, I can't find the article that I was referring to in the note that you asked about, but I think that I can remember enough of it, combined with other sources, to give a reasonable answer to your question. There are three tumor types that most closely fit into the plasmacytoma category. They are extramedullary plasmacytomas (usually occur on the skin or in the oral cavity, can occur in other places), solitary osseous plasmacytomas and multiple myelomas. While these tumors are related due to the cell type, they have somewhat different prognoses and are treated differently due to this. Extramedullary plasmacytomas usually occur in older dogs. The cutaneous or skin origin plasmacytomas are usually solitary tumors. When multiple plasmacytomas are present it is always best to look for underlying multiple myeloma. Based on several studies, only about 1% of dogs with cutaneous plasmacytomas will develop multiple myeloma. When the plasmacytomas occur in the digestive tract (I think this includes oral ones) the rate of malignancy is higher but I am not sure how much higher and often only involves metastasis to regional lymph nodes. When dogs have signs of multiple myeloma first and then develop plasmacytomas it is probably due to spread of the multiple myeloma and I don't think that the data in which the 1% figure came from included any dogs that started out with multiple myeloma. Solitary osseous plasmacytomas are much more likely to develop into multiple myeloma and I think the general impression is that most of these tumors will eventually become multiple myeloma. It is considered best to look for signs of multiple myeloma anytime that a solitary osseous plasmacytoma is diagnosed. It is apparently not helpful to initiate chemotherapy prior to the development of identifiable multiple myeloma, though. Surgical excision of the osseous plasmactyoma followed by close observation for progression of the disease seems to be the standard recommendation. Multiple myelomas are a malignant tumor that arise in the bone marrow and can cause serious side effects, including osteoporosis, discrete bone loss (lysis), unexplained bleeding episodes, increased drinking and urinating due to high blood calcium levels and/or kidney damage, weight loss, neurologic disorders including blindness and increased susceptibility to infection. Multiple myelomas are usually treated with melphalan and prednisone. Prednisone is usually used at 0.5mg/kg (about 1mg per 4 lbs) and it is usually used for about 60 days and then discontinued but for many diseases prednisone is used in dosages as high as 2mg/kg (about 1mg/lb) and may be used for long periods of time, so higher dosages and longer treatment periods are probably tempting when they seem necessary. I don't know how much it helps but I don't know of any better suggestion, either. Cyclophosphamide and chlorambucil have been used as alternative chemotherapeutic agents but I do not know how successfully. There are some reports of other "rescue" therapies for multiple myeloma, including combinations of doxorubicin, vincristine and dexamethasone (Small Animal Clinical Oncology, 2001) and liposomal doxorubricin (same source). I'm not sure what is best when you have cutaneous plasmacytomas that seem to be secondary to multiple myeloma that is otherwise responding well to therapy. I think I'd be tempted to just keep going with the chemotherapy but if your oncologist feels differently it would definitely be best to follow their advice since it will be based on more experience with these tumors than I have. Mike Richards, DVM 9/28/2001

Plasmacytoma in German Shepherd

Question: Dr. Mike, My 8 yo female GSD recently had a plasmaycytoma removed from the side of her neck. The path reports states it appears to be completely excised and well demarcated and was in the superficial dermis. This small lump looked like a red mole. My vet tells me these are rather common in some breeds, especially around the head and neck area. He also stated her prognosis was good but could not give me much insight into the possible origin of this growth. Also, I would imagine she should be checked regularly to make sure there are no more lumps. Can you give me a little more information on plasmacytomas? Thanks Pat

Answer: Pat- Plasmacytomas usually occur as a single tumor, that rises from the skin surface for a few millimeters and is about 1 to 2cm in diameter. They can get larger than this in some instances, though. They are considered to be nearly totally benign (unlikely to metastasize to other spots) but there have been a small number of reports of tumor spread or an association with multiple myeloma. Surgery is curative as long as there is a tumor free margin of tissue around the entire surgical site. These tumors are more common in German shepherd dogs than in other breeds. They usually occur on the skin or in the oral tissues. The head, neck, ears (pinnae), body and legs are also possible sites. If for some reason surgery is not possible these tumors are also reported to respond to radiation therapy well and to respond reasonably well to chemotherapy. Plasma cells are a white blood cell, which is probably why there is a slight link with multiple myelomas, another cancer of the white blood cell system. There are malignant forms of plasma cell tumors. The difference between these and the benign plasmacytomas seems to be the place they originate more than anything else. Plasma cell tumors that occur in the skin and oral tissues (extramedullary tissues) are usually benign and plasma cell tumors that arise in bone (osseous plasmacytoma) tend to be malignant. Fortunately, your dog had this tumor in the skin. I hope that this helps. The odds are very good that there will be no future problems from this tumor but it is possible that a new one would form somewhere else as well as a small chance of recurrence at or near the same spot. Just watching for signs of recurrence should be sufficient for most dogs since the cure rate is so high with surgery alone. Mike Richards, DVM 7/2/2001 Last edited 01/30/05

Plasmacytoma and Myelomas in Dogs


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Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...

 

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