Epithelioid Cellular histiocytoma is a well recognized variant of cutaneous fibrous histiocytoma that can be confused with another benign and evil one Mesenchymal lesions. It is also known as epithelioid fibrous histiocytoma and epithelioid dermatofibroma.
Histology epithelioid histiocytoma
In epithelioid histiocytoma, sections show a central location, circumscribed tumor underlying epidermal collar (figure 1). The tumor is made up of epithelioid cells arranged in sheets and sometimes a stormy pattern. Individual cells show abundant eosinophilic cytoplasm with round vesicular nuclei and prominent nucleoli (Figures 2-4). Cells may be noticeably enlarged and show some nuclear atypia (Figure 4).
There is often an associate inflammatory cell infiltrate which can be useful for diagnosis (Figure 3). Some mitosis can be seen Multinucleate giant cells and hemosmosin statement They are also sometimes seen.
Pathology of epithelioid histiocytoma.
Figure 1
Figure 2
figure 3
Figure 4
Special studies for epithelioid histiocytoma.
Immunohistochemical studies reveal positivity with Factor 13a, and there is variable positivity with CD68. ALK-1 has been increasingly recognized as being translocated in this tumor. This can be detected with immunohistochemistry or FISH.
Differential diagnosis epithelioid histiocytoma pathology
Melanoma – Amelanotic melanoma will show similar large epithelioid cells but will generally show more pleomorphism and epidermal involvement. S100 positivity is seen in melanoma.
Epithelioid sarcoma – Granulomabunches with necrosismore atypia curb+.
Other epithelioid dermal tumors: immunohistochemical studies can help exclude epithelioid vascular, smooth muscle and histiocytic tumors
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