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Updated: Aug 11, 2026
Cell Population Analyses During Skin Carcinogenesis
Published on: August 21, 2013
Epithelioid cell histiocytoma--histogenetic and kinetics analysis of dermal microvascular unit dendritic cell
Jeffrey S Silverman1, Earl J Glusac
1Southside Hospital, Department of Pathology, Bay Shore, NY, USA. peptolab@hamptons.com
Insights
Epithelioid cell histiocytoma (ECH) is a dermal tumor originating from the dermal microvascular unit. This study reveals ECH arises from activated fibroblasts and accumulating histiocytes, forming vessels and fibrous stroma.
Area of Science:
- Dermatopathology
- Tumor Biology
- Histiocytic Disorders
Background:
- Epithelioid cell histiocytoma (ECH) is a rare dermal tumor that can mimic other skin lesions.
- While often associated with FXIIIa+ histiocytic dendrocytes, the cellular origins and components of ECH remain incompletely understood.
- A potential fibroblastic contribution to ECH has not been previously characterized.
Purpose of the Study:
- To investigate the cellular differentiation and kinetics within the dermal microvascular unit in epithelioid cell histiocytoma.
- To characterize the putative fibroblastic component and its relationship with other cellular elements in ECH.
- To elucidate the cellular origins and composition of ECH.
Main Methods:
- Analysis of 12 epithelioid cell histiocytoma (ECH) cases using immunohistochemistry.
- Antibodies used included FXIIIa, CD68 (KP1), CD34, CD117, CD31, smooth muscle actin, collagen type 1 aminopropeptide, and MIB-1.
- Single and double immunostaining techniques were employed to assess cell differentiation and proliferation.
Main Results:
- ECH features CD34/CD31+ tumor vessels with myopericytes, surrounded by epithelioid-to-dendritic cells including FXIIIa+ histiocytes.
- Fibroblasts, identified by collagen type 1, were present in 11/12 cases and showed minimal pleomorphism, lacking CD34 and actin.
- Proliferation (MIB-1) was noted in fibroblasts and endothelial cells, with rare cycling histiocytes; mast cells (KP1+, CD117+) were also observed and correlated with FXIIIa+ histiocyte presence.
Conclusions:
- Epithelioid cell histiocytoma (ECH) is a vascular fibrous histiocytoma originating from the dermal microvascular unit.
- The study supports that ECH arises from activated dermal CD34+ fibroblasts and FXIIIa+ dendritic histiocytes.
- CD34+ cells differentiate into fibrocytes, contributing to collagenous stroma and vessels alongside histiocytes and mast cells.
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.
