Dermatomyofibroma
David Cassarino, MD, PhD
Key Facts
Terminology
Myofibroblastic tumor with features overlapping with dermatofibroma
Clinical Issues
Slow-growing plaque or nodule
Most cases present in shoulder and axillary regions
Microscopic Pathology
Dermal-based spindle cell proliferation
Tumor is composed of broad fascicles of elongated monomorphous spindle cells oriented parallel to surface
Elastic fibers are typically increased in numbers and fragmented, which may be highlighted with elastic stains
Top Differential Diagnoses
Dermatofibroma
Hypertrophic scar
 Scanning magnification of a dermatomyofibroma shows a dermal-based, plaque-like spindle proliferation with overlying epidermal hyperplasia, similar to a dermatofibroma. |
 Higher magnification shows a proliferation of bland spindle cells arranged in fascicles, largely running parallel to the epidermis and associated with focal collagen trapping  . |
TERMINOLOGY
Synonyms
Plaque-like dermal fibromatosis
Definitions
Myofibroblastic tumor with many features similar to dermatofibroma
ETIOLOGY/PATHOGENESIS
Unknown
May be related to trauma in some cases
CLINICAL ISSUES
Epidemiology
Incidence
Rare tumor
Age
Usually occurs in young adults
Gender
Typically females (M:F = 1:8)
Site
Most cases present in shoulder and axillary regions
Also may occur in trunk, head, and neck
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