Granular cell tumour of the breast.

Granular cell tumour of the breast (GCTB) is a rare tumour which arises from Schwann cells. It is a largely benign tumour but in extremely rare cases can exhibit malignant characteristics. It poses a particular problem as it's characteristics can mimic breast carcinoma clinically, radiologically and macroscopically. This results in the potential misdiagnosis of breast carcinoma and over treatment of patients. Typically GCTBs are benign, solitary lesions but variations include malignant GCTBs, colocalisation with breast malignancies and multicentricity. These tumours can be investigated using mammography, ultrasound and magnetic resonance imaging. However none of these modalities have yet identified any GCTB specific characteristics. On pathological examination they can be identified using both microscopic and immunohistochemical features. The cells have a distinctive granular eosinophilic cytoplasm associated with typical nuclei and abundant lysosomes. Immunohistochemically they are positive for S100 protein, CD68 and neuron specific endolase (NSE). They are treated with wide local excision and while they may reoccur, are associated with a good prognosis.