Noninvasive Encapsulated Papillary RAS-Like Thyroid Tumor (NEPRAS)

Abstract Introduction: The diagnosis of thyroid tumors arising from follicular cells that are encapsulated/well delimited and noninvasive is a challenge. When unequivocal nuclear alterations present, the final can range neoplasm with papillary-like features (NIFTP) classical/encapsulated papillary cancer (PTC), including aggressive subtypes, to poorly differentiated carcinoma. As proposed recently, presence papillae in absence exuberant (nuclear score 2), given other criteria for NIFTP met, may not be sufficient PTC. This condition called “noninvasive encapsulated RAS-like tumor” (NEPRAS), whose nature would borderline malignant. Revising our cases > 1 cm were diagnosed previously as PTC noninvasive, we found three NEPRAS. We now revised well-differentiated tumor uncertain malignant potential (WDT-UMP) because considered on occasion. Case: In 29-year-old euthyroid male patient single nodule fine-needle aspiration had revealed indeterminate cytology, measuring 3.2 was reclassified WDT-UMP For this diagnosis, met following criteria: encapsulation or clear demarcation, no vascular capsular invasion, papillae, < 30% solid/trabecular/insular growth pattern, necrosis high mitotic activity, 2. BRAFV600E mutation absent. continues show signs recurrence 7 years after lobectomy. Conclusion: Despite some (encapsulated PTC) (NEPRAS). proposal result change management, same implications those seen variant NIFTP. References: Ohba K et al. Encapsulated Papillary Thyroid Tumor Delicate Nuclear Changes KRAS Mutation Possible Novel Subtype Borderline Tumor. J Pathol Transl Med. 2019;53:136-41 AND Rosario PW. Noninvasive (NEPRAS) carcinoma (PTC). 2020;54:263-4.