RESUMO
Granular cell tumor (GCT) of the breast is a rare clinical entity, and is believed to be of schwannian origin and to follow a benign clinical course. A 50-year-old woman presented with a slowly growing mass in the right breast. Fine needle aspiration cytology revealed a cellular smear containing isolated or clustered cells showing round to oval nuclei with abundant oncocytic granular cytoplasm. Nuclei showed a fine granular chromatin pattern and occasional small single nucleoli. Cell boundaries were poorly defined, and naked nuclei were frequently found. Histologically, the tumor showed features of typical GCT, and immunohistochemical staining findings strongly supported the diagnosis. The present study demonstrates that GCT of the breast can mimic malignant lesions of breast both clinically and radiologically. The recognition of its cytologic features and suspicion of this lesion would undoubtedly aid the correct diagnosis of mammary GCT.