Primary intrafascial desmoplastic melanoma with pseudoglandular differentiation and aberrant cytokeratins expression: An exceptional presentation.

Desmoplastic melanoma (DM) is an uncommon variant of malignant melanoma (MM), histologically characterized by a mainly dermal proliferation of spindled cells within a desmoplastic stroma. Normally, involvement of deeper tissues by DM is the result of direct extension down from the overlying dermis. MM is widely known to harbor a striking potential for morphological and phenotypic variability; among MM morphological variants, pseudoglandular MM is characterized by extensive discohesion within cords and nests of malignant cells and ensuing formation of so-called pseudolumina, thus mimicking adenocarcinoma. We present an exceptional case of DM characterized by intrafascial origin, partly pseudoglandular differentiation, and aberrant experession of cytokeratins in the pseudoglandular component; genetic data from next-generation sequencing supported the final diagnosis of DM, as well as the ontogenetic identity of the pseudoglandular component. Prior to this report, pseudoglandular features had never been described in DM. Additionally, our case is unusual because of the deep origin of the tumor, arising below the subcutaneous fat of the scalp, as well as the aberrant experession of cytokeratins in the pseudoglandular component, thus posing a challenging differential diagnosis with several soft tissue tumors.