Breed: Domestic Shorthair
Gender: MALE, NEUTERED
Leg amputated, fast growing mass. Left rear limb.
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Haired skin: There is a poorly defined, dermal and subcutaneous nodule comprised of sheets of neoplastic plasma cells within a minimal fibrovascular stroma which are distinct from the overlying epidermis and are separated by a band of normal dermal collagen (Grenz zone). Neoplastic plasma cells are round with distinct cell borders and abundant eosinophilic cytoplasm. There is marked anisocytosis and anisokaryosis. Nuclei are round with coarse clumped chromatin and prominent small 1 to 4 nucleoli. There are 8 mitotic figures identified within 10 400X fields. There are associated karyomegalic forms, binucleate and multinucleate neoplastic cells, and occasional Mott cells. There is marked associated amyloid, and there are associated macrophages and multinucleated giant cells.
Left hind limb/stifle – haired skin: Plasma cell tumor
Surgical excision is complete; therefore, local recurrence is unlikely.
Plasma cell tumors are neoplasms consisting mainly of plasma cells at varying stages of differentiation. The solitary myeloma and multiple myeloma are additional types of plasma cell derived tumors. The latter are primarily located in the bone marrow. Extramedullary plasmacytomas are characterized by their extraskeletal location and are rare in cats. Such neoplasms have been described in the skin (frequently from the hind leg/tarsal area), gastrointestinal tract, retroperitoneal space, upper lip, gingiva, and orbita. Most of these tumors occur in older (10+ years of age) male cats. There is little information in the literature regarding behavior of these tumors in cats. Some reports indicate that complete excision should be curative and others state that metastasis is possible or likely. Tumor associated monoclonal gammopathy has been reported. Amyloid is more frequently found in feline extramedullary plasma cell tumors than in canine tumors.
Vet Pathol. 2003;40:249-253
Image 1: Low magnification view of the trimmed tumor.
Image 2: Higher magnification view demonstrating the neoplastic plasma cells surrounded by amyloid.