Cribriform morular variant of papillary thyroid carcinoma: clinical and cytomorphological features on fine-needle aspiration.

Background: Cribriform-morular variant of papillary thyroid carcinoma (CMV-PTC) is a rare tumor that may arise in patients with familial adenomatous polyposis (FAP), although sporadic instances of this tumor have been reported. When it arises in FAP, CMV-PTC may present before colonic manifestations are apparent, so proper identification and classification are essential for prompt assessment of the colonic disease status and genetic and familial counseling.

Methods: Nine cases of PTC with cribriform morular cytomorphology were identified at 2 large tertiary-care hospitals; 6 were true CMV-PTC with positive β-catenin and 3 were CMV-like PTC with negative β-catenin. A review of the cytomorphology and a cytology-histology correlation were performed.

Results: Only 1 patient presented with a known history of FAP. Patients presented with a median age of 41 years (range 19-64 years). There was a clear female predilection; 8 of 9 patients (89%) were female. All cases demonstrated the classical nuclear and architectural features of PTC. In addition, the most salient features were large tissue fragments with cribriform architecture and dense cellular morules. The elongated cellular shape of the tumor cells led to the misclassification of one tumor as a tall-cell variant of PTC on the FNA material.

Conclusion: CMV-PTC or CMV-like PTC demonstrate cytomorphological features that overlap with classic PTC. β-Catenin immunostaining plays an important role in making a definitive diagnosis.