Epithelioid Cell Histiocytoma
David Cassarino, MD, PhD
Key Facts
Terminology
Dermal-based benign fibrohistiocytic tumor, which can mimic melanocytic, vascular, epithelial, or other histiocytic lesions
Clinical Issues
Usually occur in young adults (mean age ˜ 40 years)
Most cases occur on extremities
Dermal nodule
Excellent; no malignant potential reported
Microscopic Pathology
Dermal-based nodular proliferation
Shows symmetry and relatively sharp circumscription
May be surrounded by an epidermal collarette
Composed of a monomorphic proliferation of enlarged, epithelioid to polygonal-appearing cells
Show round to oval nuclei, uniform vesicular chromatin, small nucleoli, and abundant eosinophilic-staining cytoplasm
 Low magnification of an epithelioid histiocytoma shows a nodular, dermal-based tumor surrounded by an epidermal collarette  . Note the prominent superficial blood vessels with telangiectasia  . |
 Higher magnification of epithelioid histiocytoma shows a proliferation of moderately enlarged, epithelioidappearing cells with eosinophilic cytoplasm and oval to angulated, hyperchromatic nuclei. |
TERMINOLOGY
Abbreviations
Epithelioid cell histiocytoma (ECH)
Synonyms
Epithelioid histiocytoma variant of dermatofibroma
Definitions
Dermal-based benign fibrohistiocytic tumor, which can mimic melanocytic, vascular, epithelial, or other histiocytic lesions
ETIOLOGY/PATHOGENESIS
Unknown
May arise from activated dermal dendrocytes
CLINICAL ISSUES
Epidemiology
