Abstract:

Perineuriomatous nevi (melanocytic nevi with perineuriomatous differentiation) are a rare and diagnostically challenging entity. While spindle cell change or neurotization of the dermal component of melanocytic nevi is a commonly seen phenomenon in conventional nevi, the presence of perineuriomatous differentiation is more unusual and can present a diagnostic challenge. We present two cases of perineuriomatous nevi, and offer a helpful histologic clue to their diagnosis. Both cases were biopsied for clinical concern for dysplastic nevus, with our first case being an irregular brown macule on the upper arm of a 33-year-old woman, and our second case presenting as a dome-shaped flank lesion on the flank of a 66-year-old woman. Histologic sections showed compound melanocytic proliferations with both a nested epithelioid junctional component as well as a prominent spindled dermal component, with spindled cells embedded in a sclerotic to myxoid and collagenous stroma. From an immunohistochemical standpoint, our first case demonstrated CD34 positivity, a marker often strongly expressed in perineuriomas. Our second case demonstrated claudin-1 positivity, also a marker of perineurioma, and the positivity of these markers supports the morphologic impression of perineuriomatous differentiation. Perhaps most intriguing, both of our cases demonstrated a limited junctional component with a relatively expansile dermal component, a sort of “reverse shoulder,” a distinguishing feature which may help in diagnosis.

Financial Disclosure:
No current or relevant financial relationships exist.

Menu

Kellen Dawson, MD