Encapsulated follicular thyroid carcinoma exhibiting glandular and spindle cell components. A case report

Spindle cell variant of follicular thyroid carcinoma: an extremely unusual case and review of the literature

Spindle cell proliferations originating in follicular derived thyroid neoplasms are rare and known to cause diagnostic conundrums. We describe a unique case of a spindle cell variant of follicular thyroid carcinoma (FTC) in a 48-year-old female without relevant past medical history, who was being followed for a 1.4 cm left thyroid nodule for the past 15 months. A fine needle aspiration (FNA) of the nodule was interpreted as benign (Bethesda II). On follow-up ultrasound the nodule demonstrated a slight increase in size (to 1.5 cm) and the appearance of coarse calcifications A repeat FNA was performed 12 months later and interpreted as malignant neoplasm (Bethesda VI), containing a population of spindle and epithelioid cells that could not be further classified. A left subtotal thyroidectomy showed an encapsulated tumor mainly composed of fibroblast-like spindle cells, extensive foci of calcifications and focal ossification, with minimal tumor capsule invasion without vascular invasion. Tumor cells expressed vimentin, ERG and SMA (focal), while being negative for pancytokeratin, thyroglobulin, TTF-1, Pax-8, calcitonin, CEA and other lineage-specific mesenchymal, neuroendocrine and melanocytic markers. Importantly, a few residual thyroid follicles were identified within the nodule, and a diagnosis of minimally invasive FTC with extensive spindle cell changes, calcification and osseous metaplasia was rendered. This is only the second cytologic report of a pure spindle cell FTC. The rarity of this neoplasm and its potential broad differential diagnosis create diagnostic difficulties both on cytology and histology.

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.

Papillary thyroid carcinoma with predominant spindle cell component: report of two rare cases and discussion on the differential diagnosis with other spindled thyroid neoplasm

Spindle cell transformation or metaplasia has been so far demonstrated in the context of both benign and malignant conditions. Spindle cell lesions of the thyroid gland of either primary or secondary origin to metastatic disease represent rare entities. We describe two patients with papillary thyroid carcinoma (PTC) showing spindle cell metaplasia, submitted to thyroidectomy due to euthyroid bilateral nodular thyroid disease. Cytological examination of fine-needle aspiration biopsy performed in the dominant nodules was consistent with follicular neoplasm in one case and with a hyperplastic/adenomatous nodule in the other patient. Histological examination disclosed unencapsulated follicular variant of PTC with spindle cell metaplasia in either cases. Both patients are doing well without clinical or laboratory evidence of PTC recurrence at 3- and 1-year follow-up, respectively. We present the clinical, pathological, and immunohistochemical aspects of these unusual cases and thoroughly discuss the differential diagnosis with other spindle cell lesions of the thyroid gland.

Spindle cell transformation of papillary carcinoma: an aggressive entity distinct from anaplastic thyroid carcinoma

Spindle cells are not routinely encountered in the context of thyroid pathology and are most often present in anaplastic thyroid carcinoma, medullary thyroid carcinoma, and benign conditions such as Riedel struma or de Quervain granulomatous thyroiditis. Only a few publications have reported papillary thyroid carcinoma admixed with a prominent spindle cell component. While these tumors are clearly distinct from anaplastic thyroid carcinoma, prognostication as to their oncologic potential is not yet established. We describe a unique case of spindle cell transformation of papillary thyroid carcinoma. The blandness of the spindle cells was so impressive as to dissuade us from a malignant diagnosis on preoperative biopsies. However, this patient unfortunately died shortly after transformation of this papillary thyroid carcinoma. We conclude that this peculiar and rare spindle cell transformation should be regarded as a potentially lethal variant of papillary thyroid carcinoma.

Cribriform-Morular Variant of Papillary Carcinoma: Association with Familial Adenomatous Polyposis - Report of Three Cases and Review of Literature

We describe a rare variant of papillary thyroid carcinoma (PTC), the Cribriform-Morular Variant (C-MV). A handful of cases have been described in the literature of this entity. They exhibit the morphologic features of a distinctive papillary neoplasm along with solid, cribriform, and squamoid-morular areas. The cribriform and morular features make this a separate entity which could be mistaken for a high grade aggressive thyroid neoplasm. These lesions are usually associated with familial adenomatosis polyposis (FAP) but rarely may be sporadic. We report three cases that we have encountered.

Spindle cell metaplasia of the thyroid arising in association with papillary carcinoma and follicular adenoma

Spindle cell proliferations of the thyroid have been described in association with reactive processes and aggressive malignant neoplasms. We describe spindle cell proliferations in 10 patients arising in association with papillary carcinoma and follicular adenoma. The spindle proliferations were 0.3 to 3.0 cm in size, constituted from 1% to 95% of the primary neoplasm, and were either admixed with the neoplastic elements or peripherally located within the primary tumor Cytologically, these proliferations showed bland-appearing spindle cells with fine chromatin and subtle nucleoli. Mitoses were rare, and inflammation was minimal. Immunostains showed reactivity with thyroglobulin, indicating their follicular origin. We believe it is important to recognize these metaplastic proliferations and distinguish them from aggressive malignant neoplasms.