Clinical Features:

• Common benign tumor of putative Schwann cell origin
• Most often seen in adults, with a female predominance
• May present in any visceral or cutaneous location
• Cutaneous lesions are most common on the trunk and extremities.
• Multiple in up to 10% of cases.
• Presents as a slow-growing mass, which may be painful, often with a verrucous appearance
• Excision is usually curative, but the rare infiltrative variants may recur.
• Rare malignant examples exist.

Histologic Features:

• Poorly defined dermal or subcutaneous tumor
• Composed of nests or trabeculae of large round to oval cells with abundant granular eosinophilic cytoplasm and small, round, uniform, central nuclei
• Pseudoepitheliomatous hyperplasia of the overlying epidermis is very common in dermal lesions.
• Positive for S-100, CD68, NSE and NKI-C3 (a putative melanoma marker).  Sometimes also positive for calretinin and α-inhibin.
• Electron microscopy reveals that the cytoplasm is filled with lysosomes, corresponding to the granules seen on H&E.
• The criteria for malignancy are not well defined.  Concerning features are size >5 cm, rapid growth, vascular invasion, necrosis, high mitotic index and pleomorphism.

Cases associated with this book:

Granular cell tumor
Author: Artur Zembowicz M.D. Ph.D.

Conference: DermatopathologyConsultations.com Teaching Collection