Folliculotropism in head and neck lentigo maligna and lentigo maligna melanoma.

Abstract

Lentigo maligna (LM) and lentigo maligna-melanoma (LMM) are histotypes of melanoma arising in skin with cumulative solar radiation damage. The extension of atypical melanocytes to the hair follicle (folliculotropism) is a histopathological feature of LM/LMM. Its role has not been totally clarified, but it may be correlated to treatment response in LM or to progression in LMM. This retrospective, multicentric study aims to identify dermatoscopic features associated with folliculotropism in LMs/LMMs. We analyzed cases of head and neck LMs/LMMs diagnosed between 2005-2014 at Melanoma Units, University of Bologna/Modena/Florence/Siena (Italy), Nice (France): 25 LMs and 73 LMMs were included. Grey circles (44%) indicated an isthmic/bulb level of involvement, which were completely absent in the infundibular LM lesions (P=0.041). In the group of LMMs, light/dark brown pseudonetwork and light brown structureless areas were an indicator of diffuse distribution of malignant melanocytes in the follicular units (P <0.001 and P=0.001, respectively), while grey circles indicated focal or diffuse distribution (P<0.001). A better understanding of the extension of malignant melanocytes is helpful, aiding clinicians in their decision to perform a radical excision or obtaining a biopsy in the most invasive area of the lesion, which includes potential folliculotropism.