Squamomelanocytic Tumor
Christine J. Ko, MD
Key Facts
Terminology
Admixed histopathologic features of both squamous cell carcinoma and malignant melanoma
Original descriptions were of dermal-based tumors
Clinical Issues
Very rare tumor
Often elderly patients
Predilection for head and neck
Unclear prognosis as so few cases reported
Microscopic Pathology
Intermingled populations of cells in dermal nodules
Squamoid population
Melanocytic population
Top Differential Diagnoses
Squamous cell carcinoma with colonization of melanocytes
Pseudoepitheliomatous hyperplasia associated with malignant melanoma
 Squamomelanocytic tumor is a dermal-based tumor composed of 2 populations of cells: Epithelioid melanocytic cells  and larger squamoid cells  . (Courtesy P. Amerio, MD, PhD.) |
 Squamomelanocytic tumor shows distinctive staining of the epithelioid cells with S100. The squamoid cells are negative  with S100. (Courtesy P. Amerio, MD, PhD.) |
TERMINOLOGY
Definitions
Admixed histopathologic features of both squamoid cells and cells that stain with melanocytic markers
2 cell types generally within < 1 mm of each other
Original descriptions were of dermal-based tumors
CLINICAL ISSUES
Presentation
Very rare tumor
< 10 cases reported in the literature
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