SkIndia Quiz 38: Subcutaneous Thumb Tumor.

A Case of Subcutaneous Thumb Tumor

A 58-year-old man presented with a 2-year history of a painless subcutaneous mass on the right thumb [Figure 1a]. The tumor had gradually increased in size and there was no preceding history of trauma. Physical examination revealed a solitary tumor on the thumb tip underneath indurate, pink skin of 1 cm size. A radiograph of the affected part revealed no abnormality. Histological examination revealed a mass composed of spindle-shaped cells [Figure 1b and c].

Figure 1

(a) Pink-colored subcutaneous nodule. (b) Well-circumscribed ovoid tumor (H and E, x40). (c) Verocay body with horizontal rows of palisading nuclei separated by areas of acellular pink basement membrane-like material (Hematoxylin–eosin stain; 100 × original magnification)

Answer

Schwannoma

Discussion

Schwannomas are benign, slow-growing tumors of neural tissue that arise from Schwann cells.[1] It is the most common tumor of the peripheral nerves; most of them are located intracranially or intraspinally, and less than 1% occurs in the hand.[2] They begin to appear between 30 and 60 years of age.[3] Presentation is as a subcutaneous mass with a fibrous capsule. Sometimes, pain is the chief complaint. Clinically, it may be difficult to differentiate from neurofibromas, giant cell tumors, ganglions, lipomas, periungual fibroma, digital fibrokeratoma, glomus tumors, and exostoses. Histological examination revealed a biphasic pattern, cellular areas of closely packed spindle cells with nuclear palisading [Figure 1b and c] (Verocay bodies) termed Antoni type A, and less cellular areas with a myxoid matrix, termed Antoni type B.[4] Histological variants are ancient, cellular, plexiform, melanotic, epithelioid, and pacinian. Surgical excision is curative and recurrence is rare.

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Conflicts of interest

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