The cytological features of sclerosing mucoepidermoid carcinoma with eosinophilia of the thyroid gland: A case report

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A total of 19 cases were identified, 3 unpublished in the authors' archives and 16 in the literature which had fine needle aspiration (FNA) material or cytologic features available for review, and were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.

Primary Thyroid Mucoepidermoid Carcinoma (MEC) Is Clinically, Prognostically, and Molecularly Different from Sclerosing MEC with Eosinophilia: A Multicenter and Integrated Study

Mucoepidermoid carcinoma (MEC) and sclerosing MEC with eosinophilia (SMECE) are rare primary thyroid carcinomas. In this study, we aimed to present our multicenter series of MEC and SMECE and integrated our data with published literature to further investigate the clinicopathological characteristics and prognoses of these tumors. We found 2 MECs and 4 SMECEs in our multicenter archives. We performed fluorescence in situ hybridization (FISH) to determine the MAML2 gene rearrangement. We screened for mutations in BRAF, TERT promoter, and RAS mutations using Sanger sequencing and digital polymerase chain reaction. Histopathologically, MECs and SMECEs were composed of two main cell types including epidermoid and mucin-secreting cells, arranged in cords, nests, and tubules. SMECEs were characterized by a densely sclerotic stroma with abundant eosinophils. We did not detect any MAML2 fusion in any of our cases. Two MEC cases harbored concomitant BRAF p.V600E and TERT C228T mutations. RAS mutations were absent in all cases. Concurrent foci of another thyroid malignancy were more commonly seen in MECs (p < 0.001), whereas SMECEs were associated with chronic lymphocytic thyroiditis (p < 0.001). MECs and SMECEs had equivalent recurrence-free survival (RFS) but MECs conferred significantly dismal disease-specific survival (DSS) as compared to SMECEs (p = 0.007). In conclusion, MECs and SMECEs not only shared some similarities but also demonstrated differences in clinicopathological characteristics, prognoses, and molecular profiles. SMECEs had a superior DSS in comparison to MECs, suggesting that they are low-grade cancers. This could help clinicians better evaluate patient outcomes and decide appropriate treatment plans.

Sclerosing mucoepidermoid carcinoma with eosinophilia of the thyroid: demonstrating the natural progression of a rare and misunderstood disease

Sclerosing mucoepidermoid carcinoma with eosinophilia of the thyroid in a 46-year-old woman.

Thyroid sclerosing mucoepidermoid carcinoma with eosinophilia in conjunction with parotid basal cell adenoma: Cytologic, histologic, and molecular features

Sclerosing mucoepidermoid carcinoma with eosinophilia (SMECE) is a rare malignancy in the thyroid: only 56 cases with histologic descriptions are reported in the literature and fewer reports describe the cytomorphology. Given the rarity of SMECE, data on the cytomorphologic and molecular features are limited. We report a case of a 53-year-old woman with a 5 cm left thyroid mass. Fine-needle aspiration (FNA) revealed atypia of undetermined significance and pathology of left thyroid lobectomy specimen showed SMECE. Additionally, a left pre-auricular lump was noted and FNA followed by left superficial parotidectomy showed basal cell adenoma. Next-generation sequencing showed point mutations in NTRK3 and NF1. Unlike salivary gland mucoepidermoid carcinoma, MAML2 translocations are not present in SMECE. Even though it is a rare entity, awareness of SMECE of the thyroid is important. In this case report we review the cytomorphologic, histologic, and molecular features.