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Case Reports

Abstract

Fibrous histiocytomas (FH) are benign mesenchymal tumors with heterogeneous morphology and biologic behavior that, in the periocular region and orbit, present a variety of histologic findings including increased cellularity, atypia, and infiltrative growth patterns that can resemble low-grade malignant spindle cell tumors, creating significant diagnostic challenges. We describe three periocular cases, two with orbital extension, representing a deep cellular variant with aneurysmal change, a dermal lesion with myofibroblastic differentiation, and an atypical variant with myxoid change. In each case, the diagnosis of FH was supported by immunoreactivity for histiocytic and fibroblastic markers such as CD68, CD163, vimentin, and/or GLUT-1, with additional immunohistochemical and molecular studies (including next generation sequencing in one case) performed as appropriate to exclude morphologic mimics. STAT6 was negative in all cases. Follow-up ranged from 10 months to over 3 years and demonstrated no evidence of recurrence. This series underscores how lesion location, morphologic diversity, and growth pattern can converge to create significant diagnostic complexity in periocular and orbital FH, while highlighting the generally favorable prognosis when complete excision is achieved.