Epithelioid cell histiocytoma – histogenetic and kinetics analysis of dermal microvascular unit dendritic cell subpopulations
Article first published online: 15 JUL 2003
Journal of Cutaneous Pathology
Volume 30, Issue 7, pages 415–422, August 2003
How to Cite
Silverman, J. S. and Glusac, E. J. (2003), Epithelioid cell histiocytoma – histogenetic and kinetics analysis of dermal microvascular unit dendritic cell subpopulations. Journal of Cutaneous Pathology, 30: 415–422. doi: 10.1034/j.1600-0560.2003.00094.x
- Issue published online: 15 JUL 2003
- Article first published online: 15 JUL 2003
- Accepted April 8, 2003
Background: 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. Thought to arise from dermal dendrocytes, most ECH contain approximately 50% FXIIIa+ histiocytic dendrocytes, but not all lesional cells express FXIIIa. A putative fibroblastic component has not been characterized.
Methods: We analyzed the differentiation and cell kinetics of dermal microvascular unit cells in 12 previously reported ECH using antibodies to FXIIIa, CD68 (KP1), CD34, CD117, CD31, smooth muscle actin, collagen type 1 aminopropeptide, and MIB-1, using single and double immunostains.
Results: In ECH, many variably sized CD34/CD31+ tumor vessels with actin+ myopericytes were surrounded by epithelioid-to-dendritic cells of three types. About 5–80% were dendritic histiocytes that expressed FXIIIa but not CD31 or KP1. Fibroblasts, in some cases showing mild nuclear pleomorphism, were usually collagen type 1+, but CD34 and actin– in 11/12 cases. One ‘early’ ECH had 40% CD34+ epithelioid cells, admixed with 50% FXIIIa+ histiocytes. Most ECH had about 2–20% KP1+, CD117+ mast cells. Mast cell numbers increased with FXIIIa+ histiocyte numbers and the intensity of FXIIIa expression. MIB-1/FXIIIa double-labeling showed only rare cycling histiocytes, with numerous cycling fibroblasts and endothelial cells.
Conclusions: Our findings support the impression that 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.