(Poster #354) Chondroblastoma-like Variant of Epithelioid Fibrous Histiocytoma: A Rare Tumor with Chondroid and Osteoid Differentiation

Abstract

We present a case of a 48-year-old female with a slightly pruritic, solitary, 4mm domed pink papule on the left upper eyelid that developed over several months. A shave biopsy was performed, with histopathology showing a cellular dermal nodule with chondroid and osteoid differentiation. Mild pleomorphism and scattered mitoses are seen, as well as osteoclast-like multinucleated giant cells and foci of calcification. Immunohistochemical stains show moderate positivity for caldesmon and weaker ALK-1 and EMA staining. Other epithelial and myoid markers are negative. FISH testing using an ALK break apart probe confirmed the presence of an ALK gene rearrangement. The chondroblastoma-like variant of epithelioid fibrous histiocytoma is a rare tumor with a predilection for the facial region. It could be confused for an epithelioid sarcoma due to EMA expression. It also needs to be differentiated from cutaneous forms of syncytial myoepithelioma, chondroma, malignant melanoma, ossifying fibromyxoid tumor, and osteosarcoma. The calcifications, EMA and ALK positivity can be used as distinguishing factors. This case adds to the growing number of this variant reported.

Financial Disclosure:
No current or relevant financial relationships exist.

Published in: ASDP 59th Annual Meeting, USA

Publisher: The American Society of Dermatopathology
Date of Conference: October 17-23, 2022