Metastatic SMARCA4-deficient thoracosarcomatoid tumor presenting as a maxillary mass: case report and review of the literature

Background Metastasis to the maxilla is exceedingly rare and may be the presenting sign of either occult malignancy or development of distant disease. Primary tumors most commonly arise from the lung but have been reported from various other sites in the body. We report a case of a patient presenting with a maxillary mass found to be a metastasis from a rare, aggressive T1N1M1 lung tumor. Case presentation A 58 year old male with significant smoking history presented to with progressively enlarging maxillary mass. Physical examination and contrast-enhanced CT revealed a 2cm maxillary mass with bony erosion, 4cm bilateral cervical lymphadenopathy, and 4.5cm left upper lobe lung mass. PET/CT showed hypermetabolic activity within the maxillary, cervical and lung lesions but also numerous metastases to the retroperitoneum, liver, and axial and appendicular skeleton.Punch biopsy was obtained. Histology showed a necrotic high-grade neoplasm with rhabdoid features. Immunohistochemistry was nonspecific, staining positively only for vimentin. Genetic analysis reported reduced to absent expression of SMARCA4 but intact SMARCB1. Clinical history and findings were consistent with SMARCA4-deficient thoracic sarcomatoid tumor with diffuse metastases. Conclusions Metastasis to the maxilla requires a high index of suspicion; biopsy is required for definitive diagnosis. Maxillary metastasis should be considered in patients with maxillary lesions in the setting of either risk factors for or prior history of malignancy. We are the first to report maxillary metastasis as presenting sign of SMARCA4-deficient thoracic sarcomatoid tumor.