Large epidermal cleft formation in verrucous-keratotic malignant melanoma of the heel
Authors: Takaaki Matsumoto, Kenji Yokota, Masaki Sawada, Yoshie Hasegawa, Aya Takeuchi, Michihiro Kono, Masashi Akiyama
Journal: Journal of the American Academy of Dermatology (2014)

To the Editor: Verrucous-keratotic malignant melanoma is an uncommon clinical variant of malignant melanoma that can be confused with benign lesions. We report a verrucous-keratotic melanoma on the heel that we had difficulty diagnosing accurately at the first examination. A 65-year-old man came to our department with a pigmented hyperkeratotic lesion on his right heel. The blackish lesion had appeared a half-year before his first visit, and it had gradually enlarged. Physical examination revealed a black, slightly elevated plaque 3.0 × 1.0 cm in size (Fig 1). The surface was ragged and covered with thick scales. Histopathologic examination of sample from shave biopsy revealed atypical melanocytes scattered throughout the horny layers. We totally excised the lesion with a wide margin. A histologic examination of the resected tumor showed prominent epidermal hyperplasia and elongated dermal papillae. Dissociation between melanoma cells in the basal layer and the suprabasal epidermis had caused a large cleft to form in the epidermis (Fig 2). Numerous atypical melanocytes were observed lining up in a row on the basement membrane.Fig 2Verrucous-keratotic malignant melanoma. An extremely large cleft is seen at the center of the tumor.View Large Image Figure ViewerDownload Hi-res image Download (PPT) We evaluated it as Clark level II, and sentinel lymph node biopsy was carried out. As a result, no metastasis was recognized in the sentinel lymph nodes. Although verrucous-keratotic malignant melanoma is not included in the widely accepted classification of Clark et al,1Clark Jr., W.H. From L. Bernardino E.A. Mihm M.C. The histogenesis and biologic behavior of primary human malignant melanomas of the skin.Cancer Res. 1969; 29: 705-727PubMed Google Scholar this case suggests that we should keep verrucous-keratotic malignant melanoma in mind as an important differential diagnosis for verrucous, hyperkeratotic lesions. In this case, the subtle perilesional clinical appearance of dark infiltration at the ridges might have been a clue to the diagnosis of melanoma. The intercellular adhesion between melanoma cells is much weaker than that between normal keratinocytes, because melanocytes or melanoma cells do not have desmosomes. In addition, membranous expression of E-cadherin, which is responsible for melanocyte-keratinocyte adhesion, is sometimes decreased in melanoma progression.2Silye R. Karayiannakis A.J. Syrigos K.N. Poole S. van Noorden S. Batchelor W. et al.E-cadherin/catenin complex in benign and malignant melanocytic lesions.J Pathol. 1998; 186: 350-355Crossref PubMed Scopus (103) Google Scholar Thinning of the epidermis with attenuation of the basal and suprabasal layers, described as “consumption of the epidermis,” is frequently seen in areas of direct contact between the epidermis and melanoma cell nests.3Hantschke M. Bastian B.C. LeBoit P.E. Consumption of the epidermis: a diagnostic criterion for the differential diagnosis of melanoma and Spitz nevus.Am J Surg Pathol. 2004; 28: 1621-1625Crossref PubMed Scopus (58) Google Scholar Consumption of the epidermis occasionally results in the formation of a cleft separating the thin epidermis and melanoma cell nests.3Hantschke M. Bastian B.C. LeBoit P.E. Consumption of the epidermis: a diagnostic criterion for the differential diagnosis of melanoma and Spitz nevus.Am J Surg Pathol. 2004; 28: 1621-1625Crossref PubMed Scopus (58) Google Scholar Braun-Falco et al4Braun-Falco M. Friedrichson E. Ring J. Subepidermal cleft formation as a diagnostic marker for cutaneous malignant melanoma.Hum Pathol. 2005; 36: 412-415Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar reported that the clefts are a reliable diagnostic criterion for malignant melanoma. It has been suggested that the greater the Breslow depth, the greater the consumption of the epidermis in a melanoma lesion.5Ohata C. Nakai C. Kasugai T. Katayama I. Consumption of the epidermis in acral lentiginous melanoma.J Cutan Pathol. 2012; 39: 577-581Crossref PubMed Scopus (6) Google Scholar However, the Breslow depth of the current lesion did not appear to be very great, although we were unable to measure it accurately because of the large size of the cleft. The presence of the verrucous architecture may be associated with the presence of epidermal consumption. In the current case, melanoma cells completely replaced the basal layer keratinocytes, forming only a single-layer lining on the basement membrane. This characteristic infiltration pattern of melanoma cells with fragile cell adhesion might have lead to the large cleft with features mimicking the tombstone appearance of pemphigus vulgaris, although in the current lesion, the tombstones were melanoma cells instead of the basal keratinocyte tombstones of pemphigus vulgaris lesions.