Breast schwannoma: review of entity and differential diagnosis

Schwannomas are benign peripheral nerve sheath tumors composed of Schwann cells, which uncommonly involve the breast. Most breast schwannomas are clinically present as a superficial palpable breast mass but may also be detected on screening mammography. Excision is the preferred treatment if symptomatic, and these are not known to recur. Histomorphology is similar to other anatomic sites: bland spindle cells with wavy nuclei, nuclear palisading (Verocay bodies), variably hypercellular (Antoni A) and hypocellular (Antoni B) areas, myxoid stroma, hyalinized vessels and variable cystic degeneration. Classic immunohistochemistry is diffuse and strong labeling for S100 and Sox10. Notable diagnostic pitfalls specific to the breast include myofibroblastoma, particularly the palisaded variant, and fascicular pseudoangiomatous stromal hyperplasia.