BREATHITT VETERINARY CENTER DIAGNOSTIC ROUNDS
Nasal Lesion in a Cat, Cytology and Histology Discordance Rafaela De Negri, DVM, MSc
Veterinary Pathologist, Assistant Professor Murray State University Breathitt Veterinary Center
A 7-year-old male cat was presented for multiple ulcerated draining lesions on the nose. A fine needle aspirate was collected for cytologic evaluation and tissue samples were collected and placed in 10% neutral buffered for- malin at 1:10 tissue: formalin ratio for histologic evaluation.
A slide was provided to Breathitt Veterinary Center for cytologic evaluation containing high cellularity and un- even distribution. Approximately 40% of the slide consisted of a thick layer. Te background was composed of mild to moderate numbers of erythrocytes and moderate numbers of bacterial cocci, rods, and filaments multi- focally arranged in large aggregates. Te vast majority of nucleated cells consisted of neutrophils, many of which were degenerated, hyper-segmented and/or contained moderate numbers of intracytoplasmic bacterial rods and cocci. Moderate numbers of macrophages occasionally containing intracytoplasmic bacteria were also present mixed with small numbers of lymphocytes and plasma cells. No fungal organisms were detected. Cytologic eval- uation suggested neutrophilic inflammation.
Four biopsy specimens ranging from 5x1mm to 8x3mm were processed for histologic evaluation. All specimens were similar and consisted of a fibrovascular stroma partially covered by colonies of basophilic bacterial rods and cocci, and infiltrated by large numbers of neoplastic round cells separated by moderate amounts of necrotic debris and abundant neutrophils. Te neoplastic cells had a nucleus to cytoplasm ratio of 2:1, scant eosinophilic cytoplasm, round to oval nuclei with stippled to peripheral chromatin clumping, and a prominent nucleolus up to 7 µm in diameter. Occasional neoplastic cells contained paranuclear clearing. Moderate anisocytosis and anisokaryosis was present; there were 27 mitotic figures in ten 400 x fields. Occasional bizarre mitotic figures and multiple binucleated cells were present. A diagnosis of malignant round cell tumor was determined. Differentials included malignant plasma cell tumor, lymphoma, histiocytic sarcoma, and high grade or anaplastic mast cell tumor.
Special staining for metachromatic granules (Toluidine blue) was negative, ruling out high grade mast cell tumor. Immunohistochemical study with round cell tumor markers (CD3, CD20, MUM-1 and CD18) was inconclusive. Although some cells presented morphologic characteristics compatible with plasma cell tumor
Figure 1. Cytology. Fine needle aspirate from multiple ulcerated draining lesions on the nose of a cat. The majority of the cells consist of neutrophils. Neutrophils are degenerated, hyper-segmented and/or contained moderate numbers of intracytoplasmic basophilic bacterial rods and cocci (arrows). (Hematoxylin and eosin stain, magnification 200x)
Continued on pg. 35 34 KVMA News - Diagnostic Rounds
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