engleski

A cutaneous plasmacytoma with chondroid metaplasia in a dog

Cutaneous plasmacytomas are common skin tumors in dogs. They are mostly solitary tumors in dogs between 4 and 13 years of age, with no sex predisposition, and the pinnae and digits are preferentially affected. Most cutaneous plasmacytomas are benign lesions, and surgical excision is usually curative. We present a cutaneous plasmacytoma with the unusual presence of chondroid metaplasia. A 2 cm, firm nodular mass was removed from the metatarsus of the left leg of a 6-year old, female American Staffordshire Terrier. Histology revealed a good demarcated, but unencapsulated tumor of round cells with an eccentrically located nucleus and a moderate amount of eosinophilic cytoplasm, corresponding to neoplastic plasma cells. Anisocytosis and anisokaryosis were pronounced, 13 mitoses were seen in 10 HPF, and bi- and multinucleated cells were scattered between neoplastic cells. Multifocally between neoplastic cells was extracellular, glassy, eosinophilic material which stained red on Kongo red stain (corresponding to amyloid). Multifocally, surrounded by neoplastic cells were foci of well differentiated cartilage. Neoplastic cells showed posi¬tive staining with CD79, while they were negative for CD3, corresponding to cells of B lymphocytic lineage. Based on histologic and immunohistochemical findings, a plasmacytoma was diagnosed. An unusual finding in plasmacytomas is the presence of cartilage between neoplastic cells, which has so far been described in three intestinal plasmacytomas. The exact pathogenesis for chondroid metaplasia is unknown, but it is hypothesized that amyloid deposits stimulate mesenchymal precursor cells to differentiate into cartilage-forming cells under the influence of soluble factors liberated from cells.

Cutaneous plasmacytoma, chondroid metaplasia, dog

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