Regressed Malignant Melanoma: Tough Dx

BOSTON — Physicians who rely on the histopathologic features of regression could mistake dysplastic nevi for regressed malignant melanoma, Ashraf Hassanein, M.D., reported in a poster presentation at the annual meeting of the American Society of Dermatopathology.

Dr. Hassanein and his associates in the departments of pathology and dermatology at the University of Florida, Gainesville, applied two sets of criteria that are used to evaluate complete and partial regression in melanoma to 777 shave or punch biopsies of benign and dysplastic melanocytic nevi taken from the backs of patients between 2002-2004.

All subtypes of nevi on the back had evidence of focal regression-like changes. Histopathologic changes that mimicked partial regression occurred with increasing prevalence in 229 junctional dysplastic nevi according to the degree of cytologic atypia they exhibited: mild atypia (10%); moderate atypia (19%); and severe atypia (39%).

“It may be possible that nevi with regression have been lumped into subtypes of melanoma regression studies in the past, hence, diluting the value of histologic regression as an independent prognostic or predictive variable in recurrence or metastases,” Dr. Hassanein suggested.