Epithelioid cell histiocytoma (ECH), also known as epithelioid fibrous histiocytoma, is a peculiar dermal tumor, which can mimic melanocytic, vascular, epithelial, or other histiocytic lesions. Epithelioid cell histiocytoma is thought to arise from dermal dendrocytes. ECH is a vascular fibrous histiocytoma.
Synopsis
epithelioid cells
FXIIIa+ histiocytes
Immunochemistry
approximately 50% FXIIIa+ histiocytic dendrocytes
CD34-
smooth muscle actin-
Localization
skin
tongue (lingual epithelioid cell histiocytoma)
Histogenesis
ECHs are speculated to originate from dermal microvascular unit and are composed of 2 primary cell populations: CD34+ primitive fibroblastic dendrocytes and factor XIIIa+ histiocytes.
ECHs putative pathogenesis entails activation of CD34+ "sentinel" reserve dendrocytes, followed by an influx of histiocytes and mast cells. Juxtacrine communication increases release of wound healing factors; suggesting a reactive etiologic component.
ECH is a vascular fibrous histiocytoma. The constituent cells appear to arise from the activation of resident microvascular CD34+ dermal fibroblasts and the accumulation of FXIIIa+ dendritic stromal assembly histiocytes.
- The CD34+ cells appear to differentiate toward collagenous fibrocytes in association with histiocytes and mast cells in forming collagenous stroma and vessels.
ECH is a tumor composed of all requisite cell types consistent with the origin from the dermal microvascular unit.
Differential diagnosis
pyogenic granuloma
melanocytic tumors
vascular tumors
epithelial tumors
histiocytic tumors
Epithelioid cell histiocytoma can mimic melanocytic, vascular, epithelial, or other histiocytic lesions.
Prognosis
Consistent with its benign course, the ECH is managed by local excision, and has an excellent prognosis.
See also
dendrocytic tumors
dermal microvascular unit
dendritic cells
- dendritic cell subpopulations
- dermal dendrocytes (FXIIIa+ histiocytic dendrocytes)
References
Silverman JS, Glusac EJ. Epithelioid cell histiocytoma—histogenetic and kinetics analysis of dermal microvascular unit dendritic cell subpopulations. J Cutan Pathol. 2003 Aug;30(7):415-22. PMID: 12859738