Clinicopathological study of acral melanoma in situ in 44 Japanese patients.

BACKGROUND

Acral lentiginous melanoma (ALM) has been a major focus of interest in Japan in the last 2 decades. A remarkable improvement recently made in the prognosis of ALM at our institution may possibly be explained by early detection including melanoma in situ.

OBJECTIVE

We have retrospectively studied 44 cases of melanoma in situ in the past 25 years from 1970 to 1994, 61% of which have been seen in the last 5 years.

RESULTS

Of 190 cases of invasive malignant melanoma including 20 melanomas involving the mucous membrane, 96 were ALM. Accordingly, the number of cases of melanoma in situ involving the acral regions was also prominent. Of 44 melanomas in situ, 29 occurred in the acral regions. Eight lesions localized on the face were compatible with lentigo maligna both clinically and histologically. All 6 mucosal lesions occurred on the oral mucosa. The remaining lesion appeared on the back of a psoriatic patient treated with photochemotherapy. Forty-two specimens showed histologically a lentiginous proliferation including atypical solitary cells within the lower portion of the epidermis, especially in the basal layer. The remaining 2 specimens were histologically of the pagetoid type.

CONCLUSION

Corresponding to the fact that ALM are predominant in the Japanese, the most common sites of melanoma in situ are also the acral regions.