Report of tall cell variant of papillary thyroid carcinoma in struma ovarii: An exceptional histology finding.

Malignant struma ovarii (SO) is very rare, and the tall cell variant (TCV) of papillary thyroid carcinoma (PTC) arising in SO is even rarer and an exceptionally unique morphological observation. A 39-year-old woman presented with lower abdominal pain and abdominal swelling. Contrast-enhanced computed tomography (CECT) of the whole abdomen revealed a multiloculated cystic mass with peripheral amorphous calcification, which was arising from the right ovary. The patient underwent a total abdominal hysterectomy and bilateral salpingo-oophorectomy. In histology, the ovary was completely replaced by thyroid parenchyma (SO) with areas of papillary thyroid carcinomatous transformation morphologically consistent with tall cell features. On immunohistochemistry (IHC), tumor cells showed expression for TTF-1 and thyroglobulin and were negative for CK19. The patient underwent total thyroidectomy, postoperative radioactive iodine ablation, and levothyroxine suppressive therapy. A three-month follow-up is uneventful. The current case not only provides insight into the diagnosis and morphological aspect of this interestingly rare occurrence but also emphasizes the need for a careful and extensive sampling of ovarian specimens.