Mammary fibromatosis (desmoid tumor) in a dog: cytological, pathological, and immunohistochemistry studies

Abstract In the present study, we describe an ill-defined firm mass in the mammary tissue in an 8-year-old terrier dog. Fine-needle aspiration (FNA) cytology showed a moderate cellularity with numerous bland bare nuclei and proliferating fibroblasts in a bloody background. Occasional clusters of spindle cells also were present. Histopathologically, a proliferation of spindle cells without atypia forming or interlacing fascicles was observed. A variable amount of collagen was seen in the background. There was no evidence of mitotic figures. Immunohistochemical analysis presented that the neoplastic cells expressed vimentin and smooth muscle actin (SMA) but did not stain for cytokeratin, S-100 protein, and CD 34. Based on cytology, histopathology, and immunohistochemical findings, the present tumor was diagnosed as mammary fibromatosis. Although fibromatosis has been reported rarely in the veterinary literature, it could be considered in differential diagnosis list of any spindle cell lesions in the breast. Histopathological examination in conjunction with the judicious use of immunohistochemistry (IHC) is required in order to reach a correct diagnosis.
Source: Comparative Clinical Pathology - Category: Pathology Source Type: research