Pigmented lesions in actinically damaged skin. Histopathologic comparison of biopsy and excisional specimens.

BACKGROUND AND DESIGN: A consecutive sample of 46 cases was collected for comparative histologic evaluation. Results of incisional biopsies of cutaneous pigmented lesions interpreted as lentigo maligna, melanoma in situ, or invasive melanoma, and those suggestive, but not diagnostic, of melanoma were collected. Those lesions that were on actinically damaged skin and in which biopsy was followed by complete excision within 6 months were included. Incisional biopsies that removed greater than 50% of the surface area of the lesion were excluded. RESULTS: Of the excisional specimens, 40% demonstrated histopathologic features more pronounced than those in the biopsy specimens. Areas of invasive melanoma not detected in the biopsy specimens were observed in 20% of the excisional specimens. Accurate diagnosis based on small biopsy specimens was not always possible because of the absence of a classic lentigo maligna histologic pattern in many cases. The most frequent deviation from the pattern was the presence of lentiginous epidermal hyperplasia within these lesions. CONCLUSIONS: These results suggest that limited sampling may be inadequate for an accurate diagnosis of pigmented melanocytic lesions on actinically damaged skin. Areas chosen for biopsy may not contain the most advanced areas histologically and may fail to detect foci of invasive melanoma elsewhere within the lesion.