Solid cell nests (SCN) in Hashimoto's thyroiditis

[Inflammatory diseases of the thyroid gland]

This review article deals with the classification, clinical features and morphology of thyroiditis. These inflammatory diseases account for approximately 20 % of all thyroid diseases. The vast majority of cases of thyroiditis are of immunogenic origin while non-immunogenic thyroiditis (caused by pathogens or iatrogenic) is a rarity.

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.

A diagnostic pitfall: Nodular tumor-like squamous metaplasia with Hashimoto's thyroiditis mimicking a sclerosing mucoepidermoid carcinoma with eosinophilia

Nodular tumor-like squamous metaplasia with Hashimoto's thyroiditis is an exceptional, benign condition presenting diagnostic difficulties for the pathologist. The main differential diagnosis is a sclerosing mucoepidermoid carcinoma (SMC) with eosinophilia. One case arising in a 50-year-old Caucasian man is reported. Histologically, the nodule consisted of large nests of squamous cells surrounded by connective tissue in Hashimoto's thyroiditis. We present the different histological criteria, allowing us to eliminate an SMC and other neoplastic tumors of the thyroid. The etiology of this tumor-like lesion, which is still under debate, is discussed.

A patient with primary squamous cell carcinoma of the thyroid intermingled with follicular thyroid carcinoma that remains alive more than 8 years after diagnosis

Primary squamous cell carcinoma of the thyroid is an extremely rare tumor with a highly aggressive clinical course. We report here on a patient with primary squamous cell carcinoma of the thyroid who remains alive more than 8 years after diagnosis. A 56-year-old man presented with a hoarse voice and a rapidly progressing mass on the right side of the thyroid gland. The patient underwent a total thyroidectomy without neck lymph node dissection. Histopathologic findings revealed primary squamous cell carcinoma combined with follicular carcinoma of the thyroid. The tumors metastasized to the cervical lymph nodes, thoracic spine and lung. He underwent 5000 rads of adjuvant radiotherapy to the neck. TSH suppressive therapy with L-thyroxine was administered alone rather than radioactive iodine therapy or chemotherapy. The patient's clinical course has been remarkable over the first 7 years; he has remained stable except for a transient paraplegia due to nerve compression. The patient underwent colectomy for the diagnosis of a colon cancer. Recent evaluation has revealed a new lesion in the lung; this was diagnosed as metastatic follicular carcinoma originating from the thyroid. High dose radioactive iodine therapy was administered, and he remains alive in stable condition.

Immunohistochemical detection of p53 homolog p63 in solid cell nests, papillary thyroid carcinoma, and hashimoto's thyroiditis: A stem cell hypothesis of papillary carcinoma oncogenesis

Most models suggest that the cell of origin of papillary carcinoma is the mature thyroid follicular epithelial cell. In a recent study, p63 was detected in papillary carcinoma, Hashimoto's thyroiditis, and in squamoid aggregates and solid cell nests (SCNs), embryonic remnants found sporadically in the fully developed thyroid. In the present study, the relationship between solid cell nests and papillary carcinoma was investigated further. Four-micrometer sections from 88 routinely fixed and processed archival thyroidectomy specimens were pretreated with citric acid pH 6.0 for antigen retrieval, then incubated overnight with anti-p63 monoclonal antibody 4A4. Slides were stained with a streptavidin-biotin kit and diaminobenzidine as chromogen and were counterstained with hematoxylin. Squamoid aggregates or SCNs were noted in 21 specimens. Several morphologic variants of SCNs were found, all of which displayed p63 positivity. These included undifferentiated SCNs and those displaying commitment toward squamoid and ciliated glandular differentiation. Small, morphologically inconspicuous aggregates of p63-positive cells were commonly found in Hashimoto's thyroiditis. Commitment of p63-positive undifferentiated cells toward thyroid follicular epithelial differentiation was occasionally noted. One SCN variant, also associated with Hashimoto's thyroiditis, was a floretlike arrangement of p63-positive cells with fusiform nuclei. p63 staining was strong and uniform in some SCNs, but in other SCNs it was compartmentalized and homologous to stem cell-staining patterns in normal squamous or bronchial epithelia. Stem cell-like staining, associated with compartmentalized p63 staining or p63-positive undifferentiated cells, was noted in 7 of 27 papillary carcinomas. p63 immunostaining is a highly sensitive means of detecting SCNs. p63 expression patterns in SCNs and a subset of papillary carcinomas are closely homologous to stem cell-associated p63 staining patterns that have been described elsewhere in squamous and bronchial epithelia. We propose a stem-cell-associated model of papillary carcinoma oncogenesis that suggests that (1) p63-positive embryonal remnants rather than mature follicular cells are the cells of origin of a subset of papillary carcinomas; (2) these p63-positive cells are pluripotent and may stay undifferentiated or undergo benign squamoid or glandular maturation, may undergo thyroid follicular epithelial differentiation, may undergo oncogenic change leading to papillary carcinoma, or may trigger an immune reaction, resulting in lymphoid infiltration and Hashimoto's thyroiditis; and (3) Hashimoto's thyroiditis and papillary carcinoma may therefore be linked etiologically, because both disorders may be initiated by the same population of pluripotent p63-positive embryonal stem cell remnants.

Primary squamous-cell carcinoma of the thyroid gland: new evidence in support of follicular epithelial cell origin

Primary squamous-cell carcinoma (SCC) of the thyroid gland is extremely rare. We had an opportunity to treat two such cases recently. Two elderly females presented with left lobe thyroid swelling that had a history of long-standing goiter. Fine-needle aspiration (FNA) of the thyroid nodule was done in both cases. FNA cytology showed an thyroid abscess in the first, and a Hürthle-cell neoplasm in the second case. Histopathologic diagnosis was a well-differentiated squamous-cell carcinoma with an adjacent area of lymphocytic thyroiditis in the first case, and a moderately differentiated squamous-cell carcinoma in association with a Hürthle-cell adenoma in the second case. Serial sections of the excised gland ruled out any other associated thyroid malignancy. Immunostaining for pan-cytokeratin, thyroglobulin, and calcitonin were performed. The tumor, comprising polygonal and spindle cells, showed positive staining for cytokeratin and thyroglobulin; however, calcitonin did not stain any structures. Exhaustive clinical, endoscopic, and radiological examinations, i.e., X-ray of the chest, contrast-enhanced computer tomography (CECT) of the neck and chest, and ENT checkup in both cases did not reveal any primary site of squamous-cell carcinoma as the likely source of the metastases, or any contiguous spread from neighboring structures. Both patients had ipsilateral nodal metastases, and both succumbed to the disease within 6 mo of histological diagnosis. The interesting observation in both cases was thyroglobulin positivity, indicating a follicular epithelial cell origin of the SCC.

Intrathyroidal lymphoepithelial cyst. A report of two cases not associated with Hashimoto's thyroiditis

Two cases of intrathyroidal lymphoepithelial cyst are described. Both of them were solitary, one being found incidentally in a patient operated on for a multinodular goiter, the other being clinically obvious as a cold nodule. They exhibited features of cysts of branchial cleft origin, i.e. squamous cell lining epithelium and abundant lymphoid tissue with reactive germinal centers. The thyroid gland parenchyma showed a discrete lymphoid infiltration consistent with the diagnosis of focal lymphocytic thyroiditis. In the first case a single epidermoid solid cell nest was found. The histogenesis of intrathyroidal lymphoepithelial cysts remains unclear, but their origin from cystically degenerated ultimobranchial body remnants (solid cell nests) seems to be most probable. This assumption is supported by a similar immunohistochemical profile of solid cell nests and epithelial cells lining the cysts and also by the presence of one solid cell nest in the proximity to the cyst in one of our cases.

Sclerosing mucoepidermoid carcinoma with eosinophilia of the thyroid: report of two patients, one with distant metastasis, and review of the literature

Sclerosing mucoepidermoid carcinoma with eosinophilia (SMECE) is a recently recognized malignant neoplasm of the thyroid gland. Two additional cases of this condition which occurred in a 70-year-old woman and a 69-year-old woman are presented. The case of the 70-year-old woman (patient 1) is the first report of distant metastasis, besides lymph node metastasis, for this type of tumor. The patient initially presented with a thyroid mass, and the thyroid gland with surrounding cervical lymph nodes was removed. Because of focal keratin "pearl" formation, the tumor was misinterpreted as a metastatic squamous cell carcinoma to the thyroid. Approximately 4 years later, the patient developed a left supraclavicular mass and lung densities. A pathological fracture of the right humeral head followed, and the left supraclavicular mass recurred along with newly developed subcutaneous nodules on the chest wall and arm. Open lung and bone biopsies revealed metastatic SMECE, which was morphologically identical to that of the thyroid mass. The 69-year-old woman (patient 2) had, in 1983, undergone thyroidectomy with left radical neck dissection; this had been diagnosed as follicular carcinoma of the thyroid with lymph node involvement. After multiple isolated lymph nodes metastases, the patient developed locally extensive, recurrent tumor that showed microscopic features of SMECE. Review of the previous thyroid tumor and lymph nodes revealed the same type of histology. To our knowledge, only a single report containing eight cases of this distinctive carcinoma of the thyroid has been published. Herein we describe characteristic morphological features of two additional cases of this rare malignancy, one with distant metastasis, and we review the related literature.

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.

Intrathyroidal lymphoepithelial cysts of probable branchial origin

Lymphoepithelial cysts with histological features characteristic of branchial cleft cysts have been reported to occur rarely in the thyroid gland. To our knowledge only six cases of this lesion have been reported. Since these reports brought this entity to our attention, we have noted that intrathyroidal lymphoepithelial cysts are not rare lesions. We report six further cases; four were incidental histological findings, and two lesions were clinically detected masses. Each of the cysts had a squamous epithelial lining with abundant underlying lymphoid tissue, including lymphoid aggregates with large reactive germinal centers. All cases were associated with chronic lymphocytic thyroiditis. Because of the histological resemblance to branchial cleft cysts, it is postulated that these lymphoepithelial cysts are branchial in origin. The histogenesis of branchial cleft cysts is unknown; however, the ultimobranchial body, originating from branchial pouches four and/or five, contributes to the embryological development of the thyroid. Branchial cleft derivatives, such as thymus and parathyroid, develop in close association with the thyroid and may be found within the thyroid gland. These branchial cleft-like cysts also may arise from branchial cleft derivatives, and their enlargement may be related to the immunological mechanisms associated with autoimmune thyroiditis.

The pathology of autoimmune thyroid disease: a review

Lymphocytic infiltration of the thyroid gland is the pathologic hallmark of autoimmune thyroid disease. Lymphoid cells are seen in the stroma of glands affected by Graves' disease. However, large lymphoid infiltrates are characteristic of that spectrum of diseases conveniently termed chronic lymphocytic thyroiditis. In this review, the pathology of the various subtypes of chronic thyroiditis is enumerated, including recently defined lesions, i.e., painless thyroiditis, thyroiditis associated with interleukin chemotherapy, and peritumor thyroiditis are reviewed. The unifying morphologic characteristics seen in these conditions are discussed.

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.

Solid cell nests of the thyroid gland

The histogenesis and clinical significance of solid cell nests (SCN) of the thyroid are not fully understood. From August 1987 to December 1989 a total of 2544 patients with thyroid and parathyroid diseases underwent surgery at Ito Hospital, and SCN were revealed within the thyroid parenchyma in 21 (0.8%). Distribution of SCN was not limited to the upper one-third of the lateral lobe, and SCN were found even in the isthmus lobe. In 5 cases microcysts were also noted within SCN, and their content was thought to be acidic proteoglycan. Immunohistochemical study revealed that SCN were negative for thyroglobulin and calcitonin but positive for carcinoembryonic antigen. Thirteen of 21 cases showed positive immunostaining with cytokeratin. Scattered calcitonin-positive cells were noted around the SCN. It is suggested from these findings that SCN of the thyroid are closely related to certain cells of ultimobranchial body vestiges which may be not of neuroectodermal origin but of endodermal origin.

Mucoepidermoid carcinoma of the thyroid gland

An extremely rare case of mucoepidermoid carcinoma of the thyroid in a 56-year-old woman is presented. The patient clinically having Hashimoto's thyroiditis was noted a nodule in her neck. The tumor was sited in the midportion of the left lobe of the thyroid, and histologically it showed both squamous features and mucin production. The squamous cells were arranged in solid sheets with horny pearls and the mucous cells tended to line dilated duct-like elements. Ultrastructurally, the epidermoid cells had aggregates of tonofilaments and well-developed desmosomal attachments, and the mucous cells contained numerous mucin granules in their cytoplasm. Immunohistochemical studies revealed that cytokeratin antibodies showed positivity for both the lining cells and squamous cells, whereas carcinoembryonic antigen positivity was found in the lining cells and intraluminal material. The tumor cells were negative for thyroglobulin, calcitonin, vimentin, chromogranin, and neuron-specific enolase. These unusual histologic and immunohistochemical features are suggestive of a tumor related to the so-called "solid cell nest" of the thyroid.

Solid cell nests of the thyroid

The ultimobranchial thyroid solid cell nests (SCN), irregular structures of about 1 mm in maximal diameter, are usually found in the middle third of the thyroid lateral lobes. SCN are basically composed of non-keratinizing epidermoid cells which lack intercellular bridges and are immunohistochemically positive for a panel of high and low molecular weight keratin proteins, as well as for carcinoembryonic antigen. In addition, SCN display isolated or grouped peripheral calcitonin-immunoreactive 'clear' (C) cells in up to 54 per cent of cases. The SCN central lumen, when present, is usually surrounded by mucinous cells; in addition, it may contain desquamated cells, cell debris, acid mucosubstances, characteristic PAS-positive granular material after diastase treatment, and colloid-like material. The so-called mixed follicles, structures lined by epidermoid cells of SCN and follicular epithelium, are often found as an additional component of the ultimobranchial remnants. The relationship of SCN to thyroid parenchymal cells and the probable implications of the thyroid 'ultimobranchial system' to tumour histogenesis are analysed. Pitfalls that may emerge with regard to SCN in practical pathological approaches are emphasized.