Solid cell nests of the thyroid gland

Clinical and pathological implications of concurrent autoimmune thyroid disorders and papillary thyroid cancer

Cooccurrences of chronic lymphocytic thyroiditis (CLT) and thyroid cancer (DTC) have been repeatedly reported. Both CLT and DTC, mainly papillary thyroid carcinoma (PTC), share some epidemiological and molecular features. In fact, thyroid lymphocytic inflammatory reaction has been observed in association with PTC at variable frequency, although the precise relationship between the two diseases is still debated. It also remains a matter of debate whether the association with a CLT or even an autoimmune disorder could influence the prognosis of PTC. A better understanding about clinical implications of autoimmunity in concurrent thyroid cancer could raise new insights of thyroid cancer immunotherapy. In addition, elucidating the molecular mechanisms involved in autoimmune disease and concurrent cancer allowed us to identify new therapeutic strategies against thyroid cancer. The objective of this article was to review recent literature on the association of these disorders and its potential significance.

Solid cell nests in Hashimoto's thyroiditis sharing features with papillary thyroid microcarcinoma

Solid cell nests (SCN) associated with Hashimoto's thyroiditis may show some atypical nuclear features including prominent nuclear grooves, enlarged overlapping nuclei and nuclear clearing. These features are sometimes mistaken for papillary thyroid microcarcinomas especially when the SCN are numerous. We reviewed SCN associated with Hashimoto's thyroiditis in 12 patients selected from 1,420 archival routinely processed formalin-fixed, paraffin-embedded thyroid specimens of Hashimoto's thyroiditis in which there was more than ten SCN per slide. In addition to the atypical nuclear features, there was a distinct eosinophilic basement membrane surrounding the SCN. Immunohistochemical analysis showed that the SCN were strongly positive for p63, stained weakly for TTF-1 and were negative for thyroglobulin, HBME-1, and calcitonin. This was compared to papillary thyroid microcarcinomas which were strongly positive for thyroglobulin, TTF-1, HBME-1, and variably positive for p63, while calcitonin and chromogranin were negative. These histological and immunophenotypic features can be used to distinguish SCN from papillary thyroid microcarcinomas associated with Hashimoto's thyroiditis.

p63 expression in solid cell nests of the thyroid: further evidence for a stem cell origin

Solid cell nests of the thyroid are embryonic remnants of endodermal origin that may be difficult to distinguish from squamous metaplasia, metastatic squamous carcinoma, papillary microcarcinoma, medullary carcinoma, and C-cell hyperplasia. These embryonic structures are composed of main cells and C-cells; cystic structures and mixed follicles are sometimes observed intermingled with solid cell nests. Recently, p63, a p53 homologue that is consistently expressed in basal/stem cells of stratified epithelia and plays a major role in triggering the differentiation of some specific cell lineages, has been characterized. We evaluated the immunohistochemical expression of p63, cytokeratins (CAM 5.2, AE1/AE3, 34betaE12, 7, and 20), carcinoembryonic antigen, thyroid transcription factor 1 (TTF-1), thyroglobulin, and calcitonin using the streptavidin-biotin-peroxidase complex technique in 6 bona fide solid cell nests. We observed that main cells of solid cell nests are strongly decorated by p63, while C-cells and all other thyroid structures were consistently negative. Moreover, main cells expressed carcinoembryonic antigen and all cytokeratins but cytokeratin 20 and lacked TTF-1, thyroglobulin and calcitonin. In contrast to this, C-cells of solid cell nests were immunoreactive for calcitonin, CAM 5.2, AE1/AE3, and cytokeratin 7; focal immunoreactivity for TTF-1 was also observed in some C-cells. We conclude that main cells of the solid cell nests display a basal/stem cell phenotype (p63 and basal cytokeratin positivity), whereas C-cells show features of parafollicular differentiation. We conclude, furthermore, that p63 antibodies may help in distinguishing solid cell nests from their mimics.

Evaluation of the role of mammalian thyroid parafollicular cells

In this report recent views are presented on the role of the parafollicular cells (PF) in the mammalian thyroid. Contemporary studies indicate morphological and functional heterogeneity of the PF cell population. In normal conditions most PF cells synthesize and secrete calcitonin (CT) and therefore they are frequently referred to as C cells. It seems however, that the contribution to the regional intrathyroidal regulation of secretion and growth processes is also an important role of all functionally mature PF cells of APUD (amine precursor uptake and decarboxylation) series. This has been confirmed by the latest reports on PF cells secreting numerous regulatory peptides (RP) usually defined as "paracrine" and/or "autocrine factors". These peptides are produced jointly with other RP in the same PF cells. Some of RP like CT, somatostatin, katacalcin I (CCP-I), CCP-II, gastrin-releasing peptide, thyroliberin and helodermin have been found in the PF cells, exclusively. Other RP, including calcitonin gene-related peptide, N-terminal peptide, neuromedin U, cholecystokinin and secretory peptide-I, have been simultaneously observed in the PF cells and intrathyroidal nerve fibres. Genetic mechanisms involved in RP production in the PF cells and possible path ways by which these peptides affect the adjacent follicular cells in the thyroid are discussed.

Primary mucoepidermoid carcinoma of the thyroid gland: a report of six cases and a review of the literature of a follicular epithelial-derived tumor

Primary mucoepidermoid carcinomas of the thyroid gland are uncommon tumors of low-grade malignant potential. We report six cases of thyroid mucoepidermoid carcinoma, four occurred in women and two in men with an age range of 29 to 57 (median, 46 years). The clinical presentation was that of a painless mass. Radiographic studies showed a single, solid, "cold" nodule in either the right or left lobe, or isolated to the isthmus. There was no history of a mucoepidermoid carcinoma developing in more typical locations (eg, salivary gland) in any of the patients. Histologically, the tumors were characterized by an intimate admixture of squamoid/epidermoid cells and mucocytes. The tumors were delineated but not encapsulated with prominent cyst formation and a variable amount of associated fibrosis. The squamoid component showed horny pearl formation, individual cell keratinization and/or the presence of intercellular bridges. Intracytoplasmic and luminal epithelial mucin was observed in all cases. In three of the cases a prominent eosinophilic cellular infiltrate was intimately identified within the neoplastic proliferation. One other case was noteworthy for the presence of ciliated epithelium. In all of the cases the uninvolved thyroid tissue showed the presence of lymphocytic thyroiditis. Rare foci of squamous metaplasia were observed in two of the cases. A microscopic focus of thyroid papillary carcinoma was observed adjacent to the mucoepidermoid carcinoma in one case. Immunohistochemical evaluation of the mucoepidermoid carcinoma showed the following antigenic profile: cytokeratin (five of five), CAM 5.2 (four of four), thyroglobulin (five of six), calcitonin (none of six), chromogranin (none of six), polyclonal carcinoembryonic antigen (four of four), and monoclonal carcinoembryonic antigen (none of five). Surgical excision was the treatment of choice. All of the patients reported are alive without disease (recurrence or metastasis) over periods ranging from 1 to 15 years. Based on our findings, we believe that these tumors are of low-grade malignant potential and originate from thyroid follicular epithelial cells rather than from solid cell nests of the ultimobranchial body.

Solid cell nests of the thyroid in medullary thyroid carcinoma

Solid cell nests of the thyroid gland were studied in 44 patients with medullary thyroid carcinoma. In 10 (22.7%) patients, solid cell nests were revealed in the vicinity of tumour foci (five cases) or in the contralateral thyroid lobe and isthmus (four cases); in one case the location was indeterminate. In all seven cases in which immunohistochemical studies were carried out, solid cell nests showed negative staining for thyroglobulin, calcitonin and chromogranin A, findings which were distinct from those in medullary thyroid carcinoma. It is therefore suggested that solid cell nests of the thyroid are not precursors of this tumour.

Ultimobranchial body nests in human fetal thyroid: an autopsy, histological, and immunohistochemical study in relation to solid cell nests and mucoepidermoid carcinoma of the thyroid

The mid portion of the lateral thyroid lobes from 64 fetuses was systematically analysed for the presence of ultimobranchial body nests. The nests showed a prevalence of 1/24 (4.2 per cent) or 13/40 (32.5 per cent) depending on whether a single- or a multi-step sectioning method was employed, respectively, and showed anatomical, morphological, and histochemical features similar to those of ultimobranchial postnatal thyroid solid cell nests. Histochemical studies revealed the presence of mucosubstances in 73 per cent of the cases, calcitonin-immunoreactive cells in 36 per cent, and both carcinoembryonic antigen and high-molecular-weight cytokeratin-immunoreactive epidermoid cells in 85.7 per cent, respectively. These findings indicate that these markers, which are also expressed by solid cell nests of the thyroid, are of value for the detection and tracing of ultimobranchial tissue to earlier stages of development. The findings of this study support the hypothesis that mucoepidermoid carcinomas of the thyroid are of ultimobranchial tissue origin.

Solid cell nests of the thyroid gland: precursor of mucoepidermoid carcinoma?

Solid cell nests (SCN) are found within the thyroid parenchyma on routine clinical pathological examinations, but their histogenesis and clinical significance are still obscure. From November 1987 to May 1991, a total of 3,260 patients underwent thyroid surgery at Ito Hospital and SCN were noted in 42 (1.3%) patients. Serial sections of the specimens from these patients were studied morphologically and immunohistochemically. The location and growth pattern of SCN within the thyroid parenchyma were distinct from those of hyperplastic C-cells. SCN were located in the isthmus lobe in 1 patient and even in the pyramidal lobe in 3 patients. In another patient neoplastic proliferation of SCN was observed. Immunohistochemically, SCN were negative for neuron-specific enolase, chromogranin A, and S-100 protein. These findings strongly suggest that SCN are of endodermal origin and that they may be closely related to mucoepidermoid carcinoma of the thyroid gland.