Molecular Pathology of Thyroid Tumors: Old Problems and New Concepts.

The molecular signatures of many thyroid tumors have been uncovered. These discoveries have translated into clinical practice and are changing diagnostic and tumor classification paradigms. Here, the findings of recent studies are presented with special emphasis on how molecular insights are impacting the understating of RAS mutant thyroid nodules, Hürthel cell neoplasms, and unusual thyroid tumors, such as hyalinizing trabecular tumor, secretory carcinoma of the thyroid, and sclerosing mucoepidermoid carcinoma with eosinophilia. In addition, the utility of detecting actionable molecular alterations by immunohistochemistry in advanced and aggressive thyroid cancer is also discussed.

Cytopathology of primary sclerosing mucoepidermoid carcinoma with eosinophilia of the thyroid: a multi-institutional case series and review of literature.

INTRODUCTION: Sclerosing Mucoepidermoid Carcinoma with Eosinophilia (SMECE) of the thyroid is an extremely rare tumor that exhibits unique histologic characteristics and is nearly always associated with lymphocytic thyroiditis (LT). However, the cytomorphologic and clinicopathologic characteristics of SMECE have only been described in rare case reports. MATERIALS AND METHODS: Authors' institution laboratory information systems were searched for records of SMECE between 2012 and 2023. Literature review was performed using keywords "Sclerosing mucoepidermoid carcinoma with eosinophilia", "thyroid", and "cytopathology" to search through institution electronic library databases for relevant articles. RESULTS: A total of 19 cases were identified, 3 unpublished in the authors' archives and 16 in the literature which had fine needle aspiration (FNA) material or cytologic features available for review, and were comprised of 3 males and 16 females. The common cytomorphologic characteristics of SMECE included fragments or loose clusters of intermediate-type epidermoid cells in a background of prominent LT and eosinophils. Overt keratinization, mucinous cells, and extracellular mucin were not commonly encountered, resulting in diagnostic challenges, especially if eosinophils associated with epithelial cell clusters were rare. The cases were reported as "Nondiagnostic" (1 case), "Atypia of Undetermined Significance" (4 cases), "Suspicious for Malignancy" (3 case), or "Malignant" (11 cases). CONCLUSIONS: The clinical course of SMECE of the thyroid varied and distinct cytomorphologic characteristics in a subset of patients who experienced aggressive disease raises the possibility of different prognostic grades. Cases with keratinized squamous cells and necrosis mimic anaplastic (undifferentiated) thyroid carcinoma, but the clinical history and radiologic findings can be helpful to exclude this diagnosis.

[Sclerosing mucoepidermoid carcinoma with eosinophilia of thyroid gland]. / Skleroziruyushchii mukoepidermoidnyi rak shchitovidnoi zhelezy s eozinofiliei stromy.

Sclerosing mucoepidermoid carcinoma with stromal eosinophilia of thyroid gland is represented less than 100 cases in the world literature. We present a rare case of sclerosing mucoepidermoid carcinona with stromal eosinophilia in a 69-year-old woman who has been observed for multinodular goiter for more than 3 years. Cytological examination revealed a picture most of all corresponding to a malignant neoplasm (Bethesda V). The patient underwent a thyroidectomy. Pathomorphological examination revealed a neoplasm of mixed structure with foci of cribriform structures and squamous metaplasia with areas of keratinization. According to the IHC study, the expression of TTF-1, p63, cytokeratins 5/6 were positive, while there were no expression of thyroglobulin with its positive reaction in the thyroid tissue. Additional histochemical staining with Alcian blue revealed a positive reaction with a homogeneous acellular substance of the tumor. A comprehensive morphological study with the use of additional stains made it possible to accurately establish the diagnosis, which will determine the further tactics of managing the patient.

Molecular Pathology of Thyroid Tumors: Old Problems and New Concepts.

The molecular signatures of many thyroid tumors have been uncovered. These discoveries have translated into clinical practice and are changing diagnostic and tumor classification paradigms. Here, the findings of recent studies are presented with special emphasis on how molecular insights are impacting the understating of RAS mutant thyroid nodules, Hürthel cell neoplasms, and unusual thyroid tumors, such as hyalinizing trabecular tumor, secretory carcinoma of the thyroid, and sclerosing mucoepidermoid carcinoma with eosinophilia. In addition, the utility of detecting actionable molecular alterations by immunohistochemistry in advanced and aggressive thyroid cancer is also discussed.

NSD3-NUTM1-rearranged carcinoma of the median neck/thyroid bed developing after recent thyroidectomy for sclerosing mucoepidermoid carcinoma with eosinophilia: report of an extraordinary case.

Sclerosing mucoepidermoid carcinoma with eosinophilia (SMECE) is an exceedingly rare low-grade thyroid malignancy of unknown histogenesis. NUT carcinoma is another rare, highly aggressive neoplasm with predilection for the midline, defined by recurrent NUTM1 fusions. The bromodomain family genes (BRD4 or BRD3) and rarely NSD3, ZNF532, or others are known fusion partners. We describe an extraordinary case of a 42-year-old female with a thyroid SMECE treated by thyroidectomy and neck dissection. She presented 6 months later with extensive midline recurrence encasing/compressing the trachea. Biopsy revealed poorly differentiated carcinoma with abrupt squamous differentiation, suggestive of NUT carcinoma. Immunohistochemistry confirmed expression of monoclonal NUT antibody. Targeted RNA sequencing revealed the NSD3-NUTM1 fusion in the NUT carcinoma, but not in the SMECE. This unique case highlights unusual sequential origin of two exceptionally rare entities at same anatomic site and underlines the necessity of sampling unexpectedly aggressive recurrences of otherwise indolent malignancies.

Mucoepidermoid carcinoma of parotid gland and membranous nephropathy - differentiation between sclerosing mucoepidermoid carcinoma with eosinophilia and Kimura's disease.

BACKGROUND: When we encounter patients who present with both a neck mass and nephrotic syndrome, both malignancy and Kimura's disease need to be evaluated as the therapeutic strategies differ vastly between them. CASE PRESENTATION: We present the case of a 27-year-old male patient with neck mass and nephrotic syndrome. The presence of both eosinophilia and elevated immunoglobulin E levels were concerning for Kimura's disease, which is an allergic syndrome defined by eosinophilic granulomas of neck soft tissue along with peripheral eosinophilia. The eventual final diagnosis, however, was sclerosing mucoepidermoid carcinoma of parotid gland with both eosinophilia and membranous nephropathy. Following the surgical resection of the mass, the nephrotic syndrome completely resolved. CONCLUSION: Detailed histopathological assessments of both the parotid gland and renal tissue were key aspects of the diagnosis and management to exclude Kimura's disease.

Activating BRAF mutation in sclerosing mucoepidermoid carcinoma with eosinophilia of the thyroid gland: two case reports and review of the literature.

BACKGROUND: Sclerosing mucoepidermoid carcinoma with eosinophilia is a rare form of thyroid carcinoma. The underlying molecular mechanisms of sclerosing mucoepidermoid carcinoma with eosinophilia tumorigenesis remain unknown. CASE PRESENTATION: We present two cases of sclerosing mucoepidermoid carcinoma with eosinophilia, both with a concurrent papillary thyroid carcinoma. Patient 1, a 70-year-old Caucasian woman, presented with sclerosing mucoepidermoid carcinoma with eosinophilia with distant renal metastasis and coexisting papillary thyroid carcinoma. Patient 2, a 74-year-old Caucasian woman with a remote history of thyroid cancer treated with thyroidectomy, presented with locoregionally invasive sclerosing mucoepidermoid carcinoma with eosinophilia and recurrent papillary thyroid carcinoma in the thyroid bed. BRAF mutation studies were performed on the sclerosing mucoepidermoid carcinoma with eosinophilia tumors. In both cases, sclerosing mucoepidermoid carcinoma with eosinophilia was positive for the BRAF V600E mutation by polymerase chain reaction. Patient 1 is the first reported case of sclerosing mucoepidermoid carcinoma with eosinophilia with renal metastasis, to the best of our knowledge. CONCLUSIONS: Our findings suggest, for the first time, to our knowledge, involvement of the RAS-RAF-MEK-ERK signaling pathway in the pathogenesis of sclerosing mucoepidermoid carcinoma with eosinophilia. Thus, BRAF inhibitors may prove to be a useful targeted medical therapy in the treatment of a subset of patients with aggressive sclerosing mucoepidermoid carcinoma with eosinophilia tumors who exhibit BRAF activating mutation.

Sclerosing mucoepidermoid carcinoma with eosinophilia of thyroid gland: Not so indolent a neoplasm?

A 58-year-old female, a known diabetic and hypertensive, presented with left-sided swelling on the anterior aspect of the neck of 1-year duration, which was rapidly increasing in size for the past 6 months. She was on Eltroxin for hypothyroidism for the past 1 year. Computed tomography study of the neck showed a nodule in the left lobe of thyroid which on fine-needle aspiration was suspicious for malignancy. Total thyroidectomy with left posterolateral lymph node dissection was done. Histopathological examination showed sclerosing mucoepidermoid carcinoma with eosinophilia (SMECE) of the thyroid gland with lymph node metastasis. SMECE of the thyroid was initially thought to be a low-grade malignancy with indolent clinical behavior. However, our case showed extra thyroidal spread with lymph node metastasis, necessitating adjuvant therapy for our patient. Such aggressive behavior has been noted in few earlier case reports also.

Thyroid sclerosing mucoepidermoid carcinoma with eosinophilia distinct from the salivary type.

We report three cases of thyroid sclerosing mucoepidermoid carcinoma with eosinophilia (SMECE), which is an extremely rare variant of mucoepidermoid carcinoma (MEC). The aims of this report were to describe the clinicopathological findings, including results from immunohistochemical and fluorescence in situ hybridization analysis of thyroid SMECE, as well as to discuss the distinction between thyroid SMECE and its salivary counterpart. The cases included a 63-year-old female, a 44-year-old male, and a 66-year-old female, with all patients presenting with Hashimoto's thyroiditis. Nodal metastasis was not found in any of the three cases. Neither regional recurrences nor distant metastases were found in any patient during the follow-up, which was 20 years, 3 years, and 18 months, respectively. Histologically, tumors were composed of epidermoid carcinoma cells, intermediate type carcinoma cells, and goblet cell-type mucus-secreting carcinoma cells, with all tumors displaying a sclerotic stroma with eosinophilic and lymphocytic infiltration. The formation of eosinophilic abscess in the tumor nests that might be a novel characteristic finding of SMECE was observed. Immunohistochemically, the carcinoma cells were positive for cytokeratin 34ßE12, TTF-1, and PAX8, but negative for thyroglobulin. In two cases, increased IgG4-positive plasma cells were observed. Mastermind-like transcriptional coactivator 2 (MAML2), according to fluorescence in situ hybridization, was intact in all cases. In conclusion, thyroid SMECE has favorable outcomes and seems to be genetically different from salivary MEC. This is the first report to describe the presence of increased IgG4-positive plasma cells in the stroma of SMECE.