Plasmacytoma is an uncommon tumor of dogs. There are two forms, medullary and extramedullary according to whether the growth is in the bone marrow or not, respectively. Today we will be discussing extramedullary plasmacytoma. This is a continuation of our series on round cell tumors which began with canine histiocytoma, followed by canine transmissible venereal tumor.
Canine extramedullary plasmacytomas are most likely to occur on mucus membranes and/or skin. The head is a common location for them, with the areas of the face, ears and lips frequently affected. However, lesions also commonly occur on the trunk as well as the feet and toes.
Typically canine extramedullary plasmacytoma is a tumor of older dogs. They arise with the appearance of raised, red nodules. Rarely is the general health of the patient affected unless the mass is in the mouth or rectum, in which case obstruction may occur.
Differential diagnosis must include multiple myeloma, especially if systemic disability is observed.
Treatment is primarily focused on surgical excision. However, given the typical locations in which they occur, surgical excision may, by necessity, be incomplete. For example, rectal and oral lesions may not allow removal of all of a tumor mass if large quantities of tissue must be excised. Sufficient skin to close a surgical site may exist for a small foot lesion, but this is a part of the body which has little skin to spare. Large lesions may require amputation.
On the other hand, growths on the trunk usually allow for wide surgical margins, removing all of the cancerous cells. In these cases prognosis is favorable.
For plasmacytomas which cannot be completely removed surgically, chemotherapy and radiation are good treatment options for many patients.
See you tomorrow, Dr. Randolph.
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