Rare Occurrence of Incidental Finding of Noninvasive Follicular Thyroid Neoplasm With Papillary–Like Nuclear Features in Hürthle Cell Adenoma

INTRODUCTION: Hürthle cell adenoma is a rare benign lesion of the thyroid gland, however, controversies about its potential malignant behavior still remain. Among thyroid neoplasms, papillary carcinoma is the most common variant with great variety of histological subtypes demonstrating different biological behavior. AIM: To raise the awareness of possible coexistence of these two lesions and discussion about possible therapeutic approaches. CASE REPORT: A 42 year old female patient was examined because of the pain in the thyroid area. Cytological examination suggested Hürthle cell adenoma. Subsequently, right thyroid lobectomy was performed. Intraoperative frozen sections confirmed the diagnosis, yet final histological analysis revealed encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC), now reclassified as noninvasive follicular thyroid neoplasm with papillary- like nuclear features (NIFTP) within the adenoma, which was not noticed through scintigraphy, ultrasound, cytological and frozen section analysis. CONCLUSIONS: Problems concerning both diagnostic and therapeutic approach to these lesions are being discussed, since opinions reported in the literature are divided, posing great challenge for the clinician in determining adequate therapeutic procedures.