Ancient schwannoma of the thumb pulp.

A 21-year-old woman had become aware of a mass on the palmar aspect of the distal phalanx of her left thumb 11 years earlier. Her medical history was unremarkable, with no traumatic injury of the left thumb. Initial examination revealed a hard but elastic, immovable tumor of 30 × 25 mm on the palmar aspect of the distal phalanx of the left thumb, with an ulcer formed at the center. No pain, sensory disturbance, or motor dysfunction was noted. The patient underwent punch biopsy at the outpatient clinic, and the tumor was histopathologically diagnosed as benign schwannoma. Total excision of the tumor was performed with digital nerve block under surgical microscope. Histopathological findings revealed a fibrous capsule covering the tumor, directional growth of tightly organized spindle-shaped cells, and mixed Antoni A and B patterns. The tumor also contained many various sized cysts and showed histological degenerative changes not observed in ordinary schwannoma, such as hemorrhage and prominent blood vessels with hyalinized walls. The S-100 stain was positive. Based on these findings, the patient was diagnosed as having ancient schwannoma. There was no evidence of infection, pain, complications such as ulcer formation, or recurrent tumor at 6 months postoperative.