Divergent differentiation or metaplastic change is a rare feature exhibited occasionally in malignant melanoma (MM), which is characterized by the development of morphologically, immunochemically, and/or ultrastructurally nonmelanocytic cells within the tumor. Smooth muscle differentiation in MM is an exceedingly rare phenomenon reported only in a few cases in the literature. We report the case of a 69-year-old woman who presented with a pure dermal amelanotic MM with smooth muscle cell differentiation and an area of rhabdoid morphology, which made the accurate histopathologic diagnostic of MM challenging.
*Department of Dermatology, Hospital Clínico Universitario Lozano Blesa, Zaragoza, Spain;
†Department of Dermatology, Fundación Jiménez Díaz, Universidad Autónoma, Madrid, Spain;
‡Department of Pathology, Complejo Hospitalario de Navarra, Pamplona, Spain; and
§Dermathopathologie Friedrichshafen, Friedrichshafen, Germany.
Reprints: Luis Requena, MD, Department of Dermatology, Fundación Jiménez Díaz, Avda, Reyes Católicos 2, Madrid 28040, Spain (e-mail: firstname.lastname@example.org).
The authors declare no conflicts of interest.