A Curious Case of Omental Oxalate Crystals in a Patient With Struma Ovarii: Pointers to an Unusual Clinicopathological Scenario.

Percutaneous image-guided biopsies are becoming increasingly common in routine pathology practice, with the greater omentum emerging as a common target. We present herein an account of a middle-aged lady with a complex ovarian mass, omental thickening, and raised serum CA125; clinically suspected to have advanced ovarian malignancy. Fine needle aspiration cytology (FNAC) from the ovarian mass was inconclusive. Omental biopsy revealed only refractile, birefringent crystalline material with surrounding foreign body giant cell reaction; thus surprising the clinical team. Subsequent resection of the ovarian mass showed a teratoma composed exclusively of thyroid tissue, diagnosed as struma ovarii. The omental crystals, interpreted as calcium oxalate crystals, were possibly a consequence of colloid seeding during the ovarian mass FNAC.