"Mucin secreting" and "mucinous" primary thyroid carcinomas: pitfalls in mucin histochemistry applied to thyroid tumours.

Abstract

suMMARY Forty primary carcinomas of the thyroid of different histological types were reviewed and studied histochemically, with the aim of identifying and assessing "mucin secretion". The patterns of extracellular "pure alcianophilia" and "mixed alcianophilia" were noted in 7-5% and about 50% of these tumours, respectively. A critical review of the pitfalls in methods and interpretation of mucin histochemistry-as performed in previously reported cases of "mucin secreting" or "mucinous" primary thyroid tumours-is presented. The apparent "mucin secretion" described in these unusual neoplasms could be due to histochemical staining of carbohydrate components or breakdown products of thyroglobulin and colloid.Cases of "mucin secreting" or "mucinous" primary carcinomas and adenomas of the thyroid have been increasingly reported in the past decade.' -19 The diagnosis of "mucin secretion" in these unusual thyroid tumours has essentially relied on the apparent positivity of different histochemical methods for mucins. These methods are more conventionally used for the study of epithelial mucins secreted by goblet cells of the gastrointestinal or bronchial tract. The major implication of these reports' -'9 has been that the follicular and parafollicular cells of the thyroidan exclusive endocrine gland, by definition-could also produce "mucins" in primary tumours, in a manner similar to that of epithelial goblet cells in exocrine organs. Does conventional mucin histochemistry applied to thyroid tumours actually identify substances, which could be regarded as being equivalent to gastrointestinal and bronchial mucins, or, alternatively, show up components or breakdown products of thyroglobulin and colloid?2In an effort to clarify further the nature of these so called "mucin secreting" or "mucinous" primary thyroid tumours we carried out a histochemical study on 40 primary carcinomas of the thyroid, using two combined staining methods for mucin identification.Accepted for publication 26 March 1987 Material and methodsThe original haematoxylin and eosin stained slides of 40 primary carcinomas of thyroid were retrieved from our files and reviewed. These 40 cases were classified according to current histological nomenclatures20 21 and included 22 papillary, nine follicular, five anaplastic, and four medullary carcinomas. All the material had been fixed in formol saline (pH 7). The paraffin blocks of these 40 cases were recut and numerous additional sections stained by two combined histochemical methods for mucins: 1 Alcian blue (pH 2.5) and periodic acid Schiff after diastase digestion (AB/PAS), which distinguishes between acidic mucins stained blue by AB and neutral mucins stained magenta by PAS (mixtures of acidic and neutral mucins produce a purple colour). 2 High iron diamine and alcian blue pH 2-5 (HID/AB), which differentiates sulphomucins stained brownish black by HID and sialomucins stained blue byAB.These two combined histochemical methods were performed in batches, with adequate positive and negative controls, and st...

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

“…The presence of stromal mucin, like those found in the present cases, may be produced by stromal fibroblasts or myofibroblasts 11. Extracellular mucin differs from epithelial mucin and is composed of uniformly sulphated acid mucin, which is stained with mucicarmine and Alcian blue but not with PAS, with or without diastase treatment 36. We retrieved 9 cases of primary thyroid neoplasms with extensive extracellular mucin deposition found in the literature 8–16.…”

Mucinous carcinoma of thyroid gland. Report of a primary and a metastatic mucinous tumour from ovarian adenocarcinoma with immunohistochemical study and review of literature

“…Mucin production in thyroid gland is an unusual event but can occur in a wide variety of thyroid lesions (follicular neoplasm, papillary carcinoma, anaplastic and medullary carcinoma) [1,2,6,8,10]. Generally, in these cases, the tumour appears characterized by a pool of mucin, often extracellular and admixed with areas of typical thyroid carcinoma.…”

“…Mucinous thyroid tumours are very rare and sometimes can occur in association with a typical thyroid carcinoma (follicular and papillary) but does not represent a true primary thyroid carcinoma [1,2,6,8,10]. This latter is exceptionally rare, with only six cases reported in literature, and histologically are indistinguishable from mucinous carcinoma of others sites [3,5,7,9].…”

Fine Needle Aspiration Cytology of Follicular Carcinoma with Clear Cell Change

“…1 The apparent "mucin secretion" is due to histochemical staining of carbohydrate components or breakdown products of thyroglobulin. [13][14][15] Some authors have suggested that the lipid accumulation is due to altered fatty acid metabolism in the tumor cells rather than to metaplasia. 10,16 The natural history of thyroid tumors with clear cell change, however, depends on their basic cytoarchitectural features rather than the presence, amount or type of clear cells.…”