Fine needle aspiration cytology (FNAC) of mammary granular cell tumour: a report of three cases

This report describes the FNAC findings in three cases of granular cell tum our of the breast. The patients comprised two females aged 59 and 62 years and one male aged 28 years. All patients presented with a breast lump which was clinically and radiologically suspicious of malignancy. FNAs yielded m oderately cellular specimens which on cytologic examination consisted of gr oups of cells and single cells with small regular nuclei and abundant granu lar cytoplasm, Bare nuclei were also present but these did not have the cha racteristic bipolar appearance of myoepithelial cells. In two cases there w as a granularity to the background. The aspirates were reported as equivoca l or atypical, probably benign, and surgical biopsy was performed. Histolog ical examination showed typical benign granular cell tumours with strong po sitive staining for S-100 protein. Pathologists should be aware that granul ar cell tumour may occur in or around the breast and should consider this d iagnosis in aspirates containing a population of cells with regular nuclei and abundant granular cytoplasm. The main cytologic differential diagnoses are likely to be apocrine cells and histiocytes. The suspicion of a granula r cell tumour should be heightened when these features are present in an as pirate from a clinically and radiologically suspicious mass. These cases hi ghlight the role of the triple approach encompassing clinical, radiological and cytological features in the assessment of a breast lesion.