Familial adenomatous polyposis-rendering a diagnosis based on recognition of an unusual primary thyroid neoplasm

Cribriform-morular variant of thyroid carcinoma: a neoplasm with distinctive phenotype associated with the activation of the WNT/β-catenin pathway

Cribriform-morular variant of thyroid carcinoma is classically associated with familial adenomatous polyposis but, it can also occur as a sporadic neoplasm. This neoplasm is much more frequently observed in women than in men (ratio of 61:1). In familial adenomatous polyposis patients, tumors are generally multifocal and/or bilateral (multinodular appearance), whereas in the sporadic cases tumors tend to occur as single nodules. The tumors are well delimited, and characteristically show a blending of follicular, cribriform, papillary, trabecular, solid, and morular patterns. Neoplastic cells are tall or cuboidal with the occasional nuclear features of classic papillary thyroid carcinoma. The morules include cells with peculiar nuclear clearing and show positivity for CDX2 and CD10. Angioinvasion and capsular invasion have been described in about 30 and 40% of cases, respectively, with lymph node metastases in less than 10% of patients and distant metastases in 6%. Although this tumor has good prognosis, neuroendocrine and/or poor differentiation have been associated with aggressive behavior. Tumor cells can be focally positive or negative for thyroglobulin, but are always positive for TTF-1, estrogen and progesterone receptors, and negative for calcitonin and cytokeratin 20. Nuclear and cytoplasmic staining for β-catenin is the hallmark of this tumor type; this feature plays a role in fine needle aspiration biopsy. Cribriform-morular variant of thyroid carcinoma has a peculiar endodermal (intestinal-like) type phenotype, activation of the WNT/β-catenin signaling pathway, and belongs to the non-BRAF-non-RAS subtype of the molecular classification of thyroid tumors. Elevated expression of estrogen and progesterone receptors and activation of the WNT/β-catenin pathway may prove useful as putative therapeutic targets in cases that do not respond to conventional therapy. Clinicians should be alerted to the possibility of familial adenomatous polyposis when a diagnosis of cribriform-morular variant of thyroid carcinoma is made. Instead of being considered as a variant of papillary thyroid carcinoma its designation as cribriform-morular thyroid carcinoma seems more appropriate.

Cribriform-morular variant of papillary thyroid carcinoma: a distinctive type of thyroid cancer

The aim of this systematic review is to study the features of cribriform-morular variant of papillary thyroid carcinoma (CMV-PTC) by analysing the 129 documented cases in the English literature. The disease occurred almost exclusively in women. The median age of presentation for CMV-PTC was 24 years. Slightly over half of the patients with CMV-PTC had familial adenomatous polyposis (FAP). CMV-PTC presented before the colonic manifestations in approximately half of the patients with FAP. Patients with FAP often have multifocal tumours in the thyroid. Microscopic examination of CMV-PTC revealed predominately cribriform and morular pattern of cancer cells with characteristic nuclear features of papillary thyroid carcinoma. Psammoma body is rare. On immunohistochemical studies, β-catenin is diffusely positive in CMV-PTC. The morular cells in CMV-PTC are strongly positive for CD10, bcl-2 and E-cadherin. Pre-operative diagnosis of CMV-PTC by fine-needle aspiration biopsy could be aided by cribriform architecture, epithelial morules and β-catenin immunostaining. Mutations of APC gene are found in the patients with CMV-PTC associated with FAP. In addition, mutations in CTNNB1, RET/PTC rearrangement and PI3K3CA mutations have been reported. BRAF mutation is negative in all CMV-PTC tested. Compared to conventional papillary thyroid carcinoma, CMV-PTC had a lower frequency of lymph node metastases at presentation (12%) and distant metastases (3%) as well as lower recurrence rates (8.5%) and patients' mortality rates (2%). To conclude, patients with CMV-PTC have distinctive clinical, pathological and molecular profiles when compared to conventional papillary thyroid carcinoma.

Cribriform-morular variant of papillary thyroid carcinoma: an indication to screen for occult FAP

Cribriform-morular variant (CMV) is a rare subtype of papillary thyroid carcinoma (PTC) that is associated with familial adenomatous polyposis (FAP). Given the high likelihood for multi-organ malignancies in FAP patients, this study explores the yield of diagnosing occult FAP among CMV-PTC patients. Institutional database was searched in order to identify patients with pathologically-confirmed CMV-PTC from 2000 to 2012. Medical records were reviewed, and clinical and pathological features were analyzed. Eleven cases of CMV were identified from 6,901 patients with PTC, for a prevalence of 0.16 %. All 11 patients were female. The median age at CMV-PTC diagnosis was 36 years (range 18-46). Two patients had pre-existing FAP at the time of PTC diagnosis. The other nine patients were referred for colonoscopy and/or genetic testing. Six patients underwent colonoscopy and one (17 %) was diagnosed with FAP based on polyposis phenotype and genetic testing. The mean age of patients at the time of CMV-PTC diagnosis was younger in the FAP group (23 years, range 18-34) than in the sporadic group (37 years, range 25-46). All three patients with FAP-associated CMV-PTC had multicentric tumors, while all five sporadic patients did not. Our study found that approximately one-sixth of patients with CMV-PTC may have occult FAP. Patients with FAP-associated CMV-PTC appear to be younger and more likely to have multicentric tumors than those with sporadic CMV-PTC. Due to the increased risk of malignancy in patients with FAP, patients with CMV-PTC should be referred for colonoscopy and/or genetic evaluation for FAP.