Follicular Adenoma with Extensive Extracellular Mucin Deposition: Report on Two Cases

Abstract

We report two cases of follicular adenoma of the thyroid with extensive extracellular mucin deposition. Fine needle aspiration in Case 1 showed singly discohesive polygonal cells in a granular mucinous background. They contained abundant eosinophilic cytoplasm, nuclear irregularities, and frequent nuclear inclusions with occasional bizarre mitoses. A right lobectomy was done. In Case 2, a 47-year-old Caucasian woman with multinodular goiter had total thyroidectomy and a yellow-tan nodule was found within the right lobe. Both tumors were well-encapsulated masses with thick capsules. Each was characterized by microfollicles without papillae in a mucinous stroma. Tumor cells were positive for thyroglobulin and negative for calcitonin, CEA, galectin-3, HBME-1, and CK19. The extracellular mucin stained with Alcian-blue and colloidal iron but not with mucicarmine and D-PAS. No BRAF gene mutation was detected. Because there were neither capsular nor vascular invasions, both cases were diagnosed as follicular adenomas of the thyroid with extensive extracellular mucin deposition, which as proposed by the WHO classification can be categorized as a mucinous variant of follicular adenoma. Retrospectively, frequent nuclear inclusions and the absence of nuclear grooves in the mucin-containing background of cytologic smears and histologic sections were shared by those of mucin-producing papillary carcinoma. It is unclear whether it belongs to an existing category of thyroid neoplasm with mucin production or whether it is truly a new tumor variant. Furthermore, pathologists should pay attention to avoid misdiagnosis of this variant of follicular neoplasm that shows an overlapping cytology with that of papillary carcinoma.

Mucin in benign thyroid nodules: treatment related change or not?

“…Thyroid adenomas or hyperplastic nodules may show this change rarely. To mention would be that thyroid nodules with prominent or extensive mucin, mainly in the stroma are reported, however as rare morphological variants [4–6]. The present cases are particular by the presence of “lake”-type zones of stromal mucin together with focal, subepithelial foci (Fig.…”

Undifferentiated (Anaplastic) Carcinoma of The Thyroid with Abundant Mucin Production

“…Thereafter, mucin production was found in a wide variety of thyroid lesions including follicular neoplasm, papillary carcinoma, anaplastic and medullary carcinoma. [2,[4][5][6][7] The possible pathogenesis of the mucin in a thyroid neoplasm enumerated as follows: [8] 1. Protein-degradation of thyroglobulin implying that mucin is produced by thyroid follicular cells www.pacificejournals.com/apalm eISSN: 2349-6983; pISSN: 2394-6466 along with radiological evidence of negative primaries elsewhere narrowed down our differentials.…”

“…Mucin producing thyroid tumours documented so far are signet ring follicular adenoma, mucoepidermoid carcinoma, sclerosing mucoepidermoid carcinoma with eosinophilia, papillary carcinoma, undifferentiated (anaplastic) carcinoma, medullary carcinoma and primary mucinous carcinoma. [1,3,5,8] Out of these, the main differential diagnosis considered in our case were metastasis from mucinous carcinomas of other regions, primary mucinous carcinoma, medullary carcinoma (spindle cell variant) and undifferentiated (anaplastic) carcinoma. Absence of mucus pool with transition to solid and glandular areas, nests of epithelial cells, amyloid deposits on histology…”

Primary ovarian mixed strumal and mucinous carcinoid arising in an ovarian mature cystic teratoma

“…The current case showed extracellular mucin deposits in the mucinous carcinoid, as well as a few foci in the strumal carcinoid, and each portion showed a different mucin staining pattern: the former was mainly epithelial mucin and the latter tissue stromal mucin. Abundant extracellular mucin is rare in struma ovarii or strumal carcinoid, as well as eutopic thyroid tissue and neoplasm, such as nodular hyperplasia, follicular adenoma, carcinoma and papillary carcinoma . The significance of extracellular mucin deposits is still undetermined in that organ, and has not yet been regarded as a histologic variant in World Health Organization (WHO) classification.…”