Axillary Peripheral Nerve Schwannoma: A Rare Occurrence in the Torso.

A schwannoma is a benign, solitary, noninvasive, and encapsulated tumor that originates from Schwann cells of the peripheral nerve sheath commonly found in the head and neck. A rare case of a benign schwannoma in the axillary region of a 34-year-old male patient is presented here accompanied by a discussion on the known entities of peripheral nerve schwannoma as well as the clinical and radiological findings coupled with treatment techniques. The patient presented with a left axillary mass of seven years gradually progressing in size which is associated with pain in the left arm. There were no neurological deficits on examination. Ultrasound and soft tissue MRI were performed followed by fine-needle aspiration cytology (FNAC), and a decision was made to take the patient up for an excisional biopsy. Histopathology revealed a tumor composed of hyper- (Antoni A) and hypocellular (Antoni B) areas, while immunohistochemistry was positive for the S-100 protein, thus confirming the diagnosis of left axillary peripheral nerve schwannoma. With such nonspecific presentation and the added challenge of its rarity, an axillary schwannoma may be easily missed and mismanaged. Surgical excision and biopsy are recommended with an aim of preserving neurological function.