Cutaneous granular cell tumor with epidermal involvement: a potential mimic of melanocytic neoplasia

Cutaneous granular cell tumor (GCT) may present with extension into the junctional region of the epidermis and thus may mimic melanocytic neoplasms.

We reviewed three cases of cutaneous GCT where a melanocytic neoplasm was either initially diagnosed or considered in the differential diagnosis. Histopathology was evaluated in regards to features associated with melanocytic neoplasms. Immunohistochemistry was performed to delineate a panel useful in the distinction of these and other entities.

All cases consisted of spindle and epithelioid cells with granular cytoplasm and bland nuclei and were centered in the superficial dermis with extension into the epidermis. Two cases resembled Spitz nevi and one case demonstrated lentiginous growth. All cases stained positively with calretinin and inhibin. Two of the three cases stained diffusely with S100 and 2/2 cases with CD56. HAM56 and CD68 were positive in one case and another showed positivity for NSE and PGP9.5. HMB-45, tyrosinase, and Melan-A were non-reactive in all cases tested.

GCT may involve the epidermis and has a growth pattern similar to melanocytic neoplasms. An immunohistochemical (IHC) panel including S100, Melan-A, tyrosinase, HMB-45, CD56, CD68, calretinin, inhibin, and PGP9.5 may aid in the distinction and may spare the patient from unnecessary morbidity.