Clinical and Histopathological Study of Benign Melanocytic Neoplasms on the Palm and Sole

Cho, Jae Joo; Chun, Duk Kyu; Lee, Yong Suk; Seo, Seung Lee; Kim, Bang Soon; Cho, Kwang Hyun; Han, Kuang Ho

Abstract

BACKGROUND: The incidence of malignant melanoma in oriental countries is lower than that in western countries. But recently the incidence of malignant melanoma and related death rate are increasing in the world. Malignant melanoma on the palm and sole is known to have worse prognosis and sometimes radical surgery such as amputation is necessary. It is important to exclude malignant melanoma when pigmented patch is encountered, and biopsy is necessary in most cases. But histopathological features of benign melanocytic neoplasms occurring at palm or sole are known to be confusing, because they can resemble the features of malignant melanoma. But there has been no report on this item in Korean dermatological literature, to our knowledge. OBJECTIVE: We investigated the histopathological features of benign melanocytic neoplasms on the palm and sole with their clinical features. MATERIALS AND METHODS: A total of 23 benign melanocytic neoplasms that had been excised from the palm and sole at Inje University Sanggye Paik Hospital and Seoul National University Hospital between July 1991 and April 1998 were evaluated. The retrospective analysis of the clinical manifestation was performed. Histologically, hematoxylin and eosin stained tissue sections were reviewed with the following criteria: symmetry, circumscription, lentiginous hyperplasia, anastomosing rete ridges, pagetoid spread, papillary dermal fibroplasia, lymphocytic infiltrate, pigment in the dermis and the stratum corneum, cytologic atypia, and mitotic activity. RESULTS: Five patients were male and eighteen were female; the mean age was 27.6 years with a peak incidence in the fourth decades. Six lesions had asymmetric, irregular and geographic borders. The diameter of the lesions varied; 3 cases were larger than 9 mm in maximum diameter. Clinically, we suspected 7 cases to be malignant melanoma before biopsy. Histological diagnoses of 23 benign melanocytic neoplasms were as follows: 12 junctional nevi, 3 compound nevi, 1 intradermal nevus, 2 lentigines, 3 benign melanocytic hyperplasias, and 2 congenital melanocytic nevi. Microscopic findings showed single melanocytic proliferation at the dermo-epidermal junction in 17 cases(73.9%), lentiginous hyperplasia in 8 cases, upward migration of melanocytes in 8 cases(34.7%), and ill-defined lateral circumscription in 6 cases(26.0%). Mitotic figures and cytologic atypia were not present. Pigments were variously seen in the stratum corneum in all cases and conspicuous amounts of melanin where the melanocytes upwardly migrated were found in 8 cases. CONCLUSION: There has been a report that the diameter of lesions is very important in differential diagnosis of malignant melanoma when a pigmented lesion is present on the palm and sole and 9mm is the critical maximum diameter. But we encountered 3 cases of benign melanocytic neoplasm which were larger than 9mm in their diameters. We think 9mm is not a reliable critical diameter in the differential diagnosis of malignant melanoma. Histological analysis showed some features resembling malignant melanoma, such as single melanocytic hyperplasia, upward migration of melanocytes in epidermis, ill-defined lateral margin, abundant pigments in the stratum corneum, and lymphocytic infiltration in dermis. There was no case with cytological atypia or mitoses and we think this is an important feature to be studied in the future in the differentiation of malignant melanoma.