Abstract:

Malignant melanocytic matricoma (MMM) is a rarely reported, malignant, cutaneous neoplasm composed of atypical matrical cells with scattered dendritic melanocytes. Here we report a case of MMM in a 92-year-old Caucasian female with a 1.2 cm red-brown nodule on the right nasal sidewall. Histology revealed a well-circumscribed dermal tumor composed of atypical matrical cells with scattered aggregates of anucleate keratinocytes (ghost cells), numerous mitotic figures (88 mitosis/10 HPF), and intermixed dendritic melanocytes (confirmed by immunoperoxidase staining with SOX-10 and MART-1). Including this case, 12 cases of MMM were identified and analyzed to investigate common clinical and histopathologic features of this rare entity. MMM commonly occurred on the head and neck (7/12 cases) of older individuals (median age of 80) with a slight male predominance (male-to-female ratio of 2.7:1) and frequently appeared clinically pigmented (9/12 cases). On histology, MMM presented as a multinodular dermal tumor composed of mitotically active (average mitotic rate of > 60 mitoses/10 HPF) atypical epithelial cells with foci of ghost cells. Dendritic melanocytes were found throughout the tumor lobules in all cases. At least focal necrosis was present in 7 of 12 cases. Despite the high mitotic rate and presence of necrosis, only 2 of 12 cases exhibited clinically aggressive behavior with recurrence following initial excision. We report this case with an unusually high mitotic rate and review the literature to increase awareness, recognition, and knowledge regarding this entity as more study is needed to form definitive diagnostic criteria for MMM.

Financial Disclosure:
No current or relevant financial relationships exist.

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Gabriella Melson, MD