Atypical histologic and immunohistochemical findings in melanocytic nevi after liquid nitrogen cryotherapy.

Two patients with atypical histologic and immunohistochemical findings in nevi after cryotherapy are reported. Patient 1, a 32-year-old white woman, presented to our cancer center with two changing moles that had been treated with liquid nitrogen therapy by her primary care provider. After cryotherapy, these two lesions showed paradoxical loss of maturation, with aberrant expression of HMB-45 in the dermal component, thereby mimicking melanoma. Although the overall Ki-67 labeling was low, focally there was no diminution in Ki-67 immunoreactivity with descent into the dermis. Patient 2, a 39-year-old white man, had a nevus treated with liquid nitrogen by his primary care physician and presented to us with a changing mole. Histologically, there was loss of maturation and aberrant HMB-45 expression. These features may pose a diagnostic dilemma, and highlight the importance of clinicopathologic correlation in arriving at the correct diagnosis.