Organized Fibrous and Calcified Thrombus of the Medial Canthus Mimicking a Dermoid Cyst: A Clinicoradiological and Histopathological Correlation

Medial canthal masses encompass a broad range of lacrimal, congenital, inflammatory, vascular, and neoplastic lesions.Their clinical and radiological features may overlap, making an accurate preoperative diagnosis challenging.We report the case of a 31-year-old woman presenting with a painless, slowly enlarging right medial canthal mass with a four-year history.Examination revealed a firm, non-tender, and non-compressible lesion without inflammatory signs, epiphora, proptosis, diplopia, or ocular motility restriction.Lacrimal irrigation confirmed a patent drainage system.Ultrasonography demonstrated an 11 × 10 mm lesion containing a central hyperechoic focus with posterior acoustic shadowing, consistent with calcification.Computed tomography dacryocystography showed a well-circumscribed medial canthal mass with central calcification and a patent ipsilateral lacrimal drainage system.A dermoid cyst was suspected preoperatively.Complete excision was performed through an external medial canthal approach.Histopathological examination demonstrated a large-caliber vascular structure with a lumen largely obliterated by an organized thrombus composed of fibrin and entrapped red blood cells, with dense fibrosis, cholesterol clefts, and dystrophic calcification.These findings established the diagnosis of an organized fibrous and calcified thrombus.The postoperative course was uneventful, with satisfactory healing and no clinically evident recurrence at the two-month follow-up.This case illustrates how advanced organization, fibrosis, and calcification can obscure the vascular nature of a lesion and closely mimic a dermoid cyst.In this case, histopathological examination was decisive in establishing the definitive diagnosis.