Abstract

Hypopigmented and achromatic melanocytic tumors with spindle cells represent a diagnostic challenge. Spindle cell nevi resemble neural tumors. Desmoplastic nevi imitate dermatofibromas. Hypopigmented and amelanotic blue nevi are variants of the common and cell-rich blue nevus with an enhanced difficulty to make a correct diagnosis due to the lack of pigment. All of the above benign melanocytic tumors with proliferations of hypopigmented spindle cells can more or less show aspects of desmoplastic melanoma. The differential diagnosis of these entities demands a combination of clinical and histological parameters as well as supporting immunostaining. Regarding desmoplastic melanoma, diagnoses frequently made are benign spindle cell neoplasms, scar or unspecific inflammatory condition. As the histological aspects can be so misleading, attention is necessary in order to make the correct diagnosis. Particular care must be taken to rule out desmoplastic melanoma in the case of spindle cell proliferations, a cicatricial or inflammatory process in the classical settings of face, volar skin, or mucous membranes. The spindle cell melanoma must be distinguished from other types of malignant spindle cell neoplasms, which can involve the skin. The differential diagnosis with such tumors is entrusted mainly to immunostaining.