Non-invasive Follicular Thyroid Neoplasm With Papillary-Like Nuclear Features (NIFTP) Arising in Struma Ovarii: A Pathologist's Perspective.

Struma ovarii is a rare monodermal ovarian teratoma predominantly composed of thyroid tissue. It is usually benign, although malignant transformation is occasionally observed. Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is a recently defined non-malignant entity with indolent behavior, and its emergence in struma ovarii is very uncommon. It requires careful histological analysis, and because of the unusual occurrence of this tumor, its management and follow-up remain challenging and debated. We report a case of NIFTP arising in struma ovarii in a 48-year-old patient. To the best of our knowledge, this is the second case report of this nature.