Multiple cutaneous plasmacytosis with multilobated (clover-leaf shaped) nuclei cells in a dog

A 12-year-old female Shih-tzu dog was presented with a 2-month history of cutaneous non-pruritic multiple ulcerated or crusted nodules of less than 1.5 cm in diameter on eyelids, lips, abdomen, groin, thighs and perianal region. Several diagnostic tests were performed, including fine needle aspiration and skin biopsy of the cutaneous nodules. Cytologic interpretation was round cell neoplasm with multilobated (clover-leaf shaped) nuclei. Histopathology revealed round neoplastic cells with prominent anisocytosis and anisokaryosis, and numerous mitotic figures; however, the origin of the cells was not identified. Immunohistochemical evaluation indicated that these cells were positive for CD79a and MUM-1, but negative for CD3, CD20 and Pax 5. The patient was treated with chemotherapy, and the skin condition improved. Despite good response to chemotherapy, the patient was euthanized due to poor general health.