• The CPG provides key recommendations and algorithms for managing SMs, excluding mucosal melanoma and soft-tissue sarcomas. • The guideline covers diagnosis, staging, risk assessment, treatment and disease monitoring. • Technological advancements in treatment with RT are discussed with a special focus on particle therapy. • Surgical indications for open and transnasal endoscopic surgery are provided. • Neoadjuvant chemotherapy in high-grade, locally advanced SMs helps to select subjects for conservative treatments.

• Keywords
• (neoadjuvant) chemotherapy, endoscopic surgery, proton therapy, radiotherapy, sinonasal carcinomas,
• Publication type
• Journal Article MeSH
• Practice Guideline MeSH

SMARCB1-deficient sinonasal adenocarcinoma is a rare variant of SWI/SNF-deficient malignancies with SMARCB1 loss and adenocarcinoma features. More than 200 high-grade epithelial sinonasal malignancies were retrieved. A total of 14 cases exhibited complete SMARCB1 (INI1) loss and glandular differentiation. SMARCA2 and SMARCA4 were normal, except for one case with a loss of SMARCA2. Next-generation sequencing (NGS) and/or fluorescence in situ hybridization (FISH) revealed an alteration in the SMARCB1 gene in 9/13 cases, while 2/13 were negative. Two tumors harbored SMARCB1 mutations in c.157C > T p.(Arg53Ter) and c.842G > A p.(Trp281Ter). One harbored ARID1B mutations in c.1469G > A p.(Trp490Ter) and MGA c.3724C > T p.(Arg1242Ter). Seven tumors had a SMARCB1 deletion. One carried an ESR1 mutation in c.644-2A > T, and another carried a POLE mutation in c.352_374del p.(Ser118GlyfsTer78). One case had a PAX3 mutation in c.44del p.(Gly15AlafsTer95). Histomorphology of SMARCB1-deficient adenocarcinoma was oncocytoid/rhabdoid and glandular, solid, or trabecular in 9/14 cases. Two had basaloid/blue cytoplasm and one showed focal signet ring cells. Yolk sac tumor-like differentiation with Schiller-Duval-like bodies was seen in 6/14 cases, with 2 cases showing exclusively reticular-microcystic yolk sac pattern. Follow-up of a maximum of 26 months (median 10 months) was available for 8/14 patients. Distant metastasis to the lung, liver, mediastinum, bone, and/or retroperitoneum was seen in 4/8 cases. Locoregional failure was seen in 75% of patients, with 6/8 local recurrences and 3 cervical lymph node metastases. At the last follow-up, 5 of 8 (62%) patients had died of their disease 2 to 20 months after diagnosis (median 8.2 months), and 3 were alive with the disease. The original diagnosis was usually high-grade non-intestinal-type adenocarcinoma or high-grade myoepithelial carcinoma. A correct diagnosis of these aggressive tumors could lead to improved targeted therapies with potentially better overall disease-specific survival.

• Keywords
• Head and neck, Next-generation sequencing, Rhabdoid, SMARCB1-deficient adenocarcinoma, SWI/SNF complex, Sinonasal, Yolk sac-like,
• MeSH
• Adenocarcinoma * genetics   pathology   MeSH
• Diagnosis, Differential MeSH
• DNA-Binding Proteins genetics   deficiency   MeSH
• Adult MeSH
• SMARCB1 Protein * deficiency   genetics   MeSH
• In Situ Hybridization, Fluorescence MeSH
• Middle Aged MeSH
• Humans MeSH
• Mutation * MeSH
• Myoepithelioma * genetics   pathology   MeSH
• Biomarkers, Tumor genetics   MeSH
• Paranasal Sinus Neoplasms * genetics   pathology   MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Neoplasm Grading MeSH
• Transcription Factors * genetics   deficiency   MeSH
• High-Throughput Nucleotide Sequencing MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• DNA-Binding Proteins MeSH
• SMARCB1 Protein * MeSH
• Biomarkers, Tumor MeSH
• SMARCB1 protein, human MeSH Browser
• Transcription Factors * MeSH