Thoracic SMARCA4-Deficient Undifferentiated Tumor

**Semantic type:** Neoplastic Process

**Definition:** An aggressive, high-grade malignant neoplasm characterized by biallelic inactivation of SMARCA4 gene. It affects adults, usually heavy smokers, and involves the thorax (lung, pulmonary hilum, mediastinum, and/or pleura) with or without chest wall invasion. It is composed of sheets of malignant large round to epithelioid cells. Rhabdoid cells may be present. Increased number of mitoses and necrosis are frequently seen. The prognosis is poor.

**Synonyms:** - SMARCA4-Deficient Thoracic Sarcoma - SMARCA4-Deficient Thoracic Sarcomatoid Tumor - SMARCA4-UT