Abstract
Malignant transformation of struma ovarii is a rare event observed in about 5% of cases. We herein illustrate an unusual case that more closely simulated "highly differentiated follicular carcinoma" (HDFCO), another entity with relatively similar appearance with malignant struma ovarii (MSO). In our case, the peritoneal and systemic dissemination occurred 18 years following excision of ovarian struma that was reported benign on histopathology. Three features in the described case were noteworthy: (i) the highly functioning nature of the lesions (evidenced by low TSH even without thyroxine suppression), (ii) low/minimal FDG avidity of the foci, that could further reiterate the well differentiated nature of these lesions as expected in HDFCO and (iii) prominent involvement of rare sites such as spleen and liver, in addition to the usual sites such as lungs, peritoneum and bilateral adnexae.
