Sclerosing mucoepidermoid carcinoma (SMEC) of the salivary glands is a rare variant of low-grade mucoepidermoid carcinoma with scanty cellular atypia characterized by marked fibrosis/sclerosis and a rich inflammatory infiltrate. Herein, we report 25 unpublished cases of SMEC, two of them with prominent eosinophilia (2/25; 8%) and three with abundant IgG4-positive plasma cells (3/25; 12%). In our series of salivary SMEC, molecular analysis using fluorescence in situ hybridization (FISH) and/or next-generation sequencing (NGS) provided evidence of MAML2 gene rearrangement in 18 cases of the 21 analyzable cases tested (86%), while this gene locus was intact in 3 cases (14%). This study focuses on the diagnostic criteria of salivary SMEC given its challenge of abundant collagenous stroma, minimal residual neoplastic areas, and inconspicuous mucous cells. Follow-up data of our cases indicate that salivary SMECs have favorable outcomes. Molecular analysis for MAML2 gene rearrangement suggests that SMECs of salivary glands represent a rare variant of conventional low-grade MECs of salivary glands. In contrast, SMECs of the thyroid gland are genetically distinct from salivary-type thyroid MECs.

• Keywords
• MAML2 rearrangement, IgG4, Keloid-like stromal fibrosis, SMEC, Salivary gland, Sclerosing mucoepidermoid carcinoma, Sclerosis, Tissue eosinophilia,
• MeSH
• DNA-Binding Proteins genetics   MeSH
• Adult MeSH
• Gene Rearrangement MeSH
• In Situ Hybridization, Fluorescence MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Carcinoma, Mucoepidermoid * pathology   genetics   MeSH
• Biomarkers, Tumor genetics   analysis   MeSH
• Salivary Gland Neoplasms * pathology   genetics   MeSH
• Aged MeSH
• Sclerosis MeSH
• Trans-Activators genetics   MeSH
• Transcription Factors genetics   MeSH
• High-Throughput Nucleotide Sequencing MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Male MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• DNA-Binding Proteins MeSH
• MAML2 protein, human MeSH Browser
• Biomarkers, Tumor MeSH
• Trans-Activators MeSH
• Transcription Factors MeSH

Classification of tumors of the head and neck has evolved in recent decades including a widespread application of molecular testing in tumors of the sinonasal tract, salivary glands, and soft tissues with a predilection for the head and neck. The availability of new molecular techniques has allowed for the definition of multiple novel tumor types unique to head and neck sites. Moreover, an expanding spectrum of immunohistochemical markers specific to genetic alterations facilitates rapid identification of diagnostic molecular abnormalities. As such, it is currently possible for head and neck pathologists to benefit from a molecularly defined tumor classification while making diagnoses that are still based largely on histopathology and immunohistochemistry. This review covers the principal molecular alterations in sinonasal malignancies, such as alterations in DEK, AFF2, NUTM1, IDH1-2, and SWI/SNF genes in particular, that are important from a practical standpoint for diagnosis, prognosis, and prediction of response to treatment.

• Keywords
• Head and neck, Molecular diagnostics, Next-generation sequencing, Sinonasal, Sinonasal tumor, Soft tissue,
• MeSH
• Humans MeSH
• Biomarkers, Tumor * genetics   analysis   MeSH
• Paranasal Sinus Neoplasms * pathology   genetics   classification   diagnosis   MeSH
• World Health Organization MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Biomarkers, Tumor * MeSH