Granular Cell Tumor of the Breast: Radiologic-Pathologic Correlation.

Granular cell tumor (GCT) is an uncommon neoplasm arising from perineural Schwann cells that can arise anywhere in the body and is particularly rare in the breast. Imaging typically shows an irregular, noncalcified mass with high density on mammography and intense posterior shadowing on US that mimics malignancy. Benign GCTs can be locally aggressive and invade the skin or chest wall. Core biopsy is necessary for diagnosis. Polygonal- to spindle-shaped cells with prominent cytoplasmic eosinophilic granules show S-100 and CD68 staining on immunohistochemistry and lack cytokeratin, estrogen, or progesterone expression. The vast majority of GCTs are benign, albeit locally infiltrative, tumors cured by wide local excision.