Epithelioid Fibrous Histiocytoma Involving Deep Dermis and Subcutaneous Adipose Tissue

Area of Science:

• Dermatopathology
• Oncology
• Histology

Background:

• Epithelioid fibrous histiocytoma (EFH) typically presents in the superficial dermis with an epidermal collarette.
• Deep dermal or subcutaneous involvement is an uncommon presentation for EFH.

Purpose of the Study:

• To describe three cases of nodular epithelioid fibrous histiocytoma involving deep dermal and subcutaneous tissues.
• To emphasize the diagnostic utility of ALK immunohistochemistry in identifying unusual variants of EFH.

Main Methods:

• Histopathological examination of three nodular lesions.
• Analysis of cellular morphology, including epithelioid cells with vesicular nuclei and eosinophilic cytoplasm.
• Application of ALK immunohistochemistry to assess cellular labeling patterns.

Main Results:

• All three cases exhibited deep dermal/subcutaneous nodules.
• Characteristic epithelioid cellular features and ALK immunoreactivity were observed.
• Lesions ranged from 0.8 to 2.0 cm and occurred in adults on the trunk or extremities.

Conclusions:

• These cases expand the known morphological spectrum of epithelioid fibrous histiocytoma.
• ALK immunohistochemistry is crucial for differentiating deep dermal EFH variants from mimics.
• Long-term follow-up (4.5-23 years) showed no recurrence in the presented cases.