Isolated long-standing painless swelling of the hand: A hidden schwannoma unveiled by histopathology

A 20-year-old female presented with a slowly progressive nodular swelling in the 3^rd finger web-space of the left hand for the past 9 years, with occasional mild dragging sensation on movement of the wrist. She had no systemic symptoms or similar family history. On examination, an ovoid swelling, approximately 3 cm in diameter, freely mobile, non-tender, non-pulsating, and firm in consistency was present over the left dorsum of the hand [Figure 1a]. There was no associated sensory loss or Tinel’s sign. Ultrasonography showed a hypoechoic soft-tissue mass without any connection to the underlying joint. Differential diagnosis of ganglion cyst, lipoma, neurofibroma, neuroma, xanthoma, and tendon-related tumors was considered. Excision showed a whitish, shiny, lobulated firm mass [Figure 1b].

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Figure 1:

(a) An ovoid nodular swelling over the dorsum of the left hand. (b) The gross specimen showed a whitish, shiny, lobulated, firm mass.

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Histopathology showed a well-encapsulated tumor with spindle-shaped cells exhibiting hypercellular and hypocellular areas [Figure 2a], Verocay bodies [Figure 2b], vascular hyalinization, and clear cells [Figure 2c]. A final diagnosis of sporadic peripheral cutaneous schwannoma was made.

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Figure 2:

(a) Well-encapsulated tumor with predominant areas composed of interweaving spindle-shaped cells forming a hypercellular area - Antoni A-type and few areas showing hypocellular area - Antoni B-type (H&E; ×40). (b) Row of palisading nuclei of spindle cells separated by fibrillary processes, also called Verocay bodies (H&E; ×400). (c) Hyalinization and dilatation of blood vessels (red arrow) and clear cell changes (black arrow) (H&E; ×400).

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These rare benign nerve sheath tumors derived from Schwann cells often affect the extremities and trunk and may be associated with neurofibromatosis-2, schwannomatosis, and Carney complex.^[1,2] Isolated cutaneous schwannoma diagnosis is clinically challenging, and histopathological correlation often differentiates it from other nodular swellings of the hands.^[3] Surgical excision provides an excellent prognosis with minimal recurrence.