Imaging performance of thoracic SMARCA4-deficient undifferentiated tumor: a case report and literature review.

ABSTRACT

Background: SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a class of high-grade malignant tumors that has only been described in recent years, with an undifferentiated or rhabdoid morphology and genetic deletion of SMARCA4 (BRG1), a subunit of the BRG1-associated factors (BAFs) chromatin remodeling complex. It is a rare tumor type that occurs in young to middle-aged men and usually presents as a compressive thoracic mass with rapid progression and poor prognosis. However, much remains unknown about the clinical and imaging manifestations of the disease. Case Description Herein, we report a 51-year-old man who came to our hospital with multiple enlarged lymph nodes in the chest after a computed tomography (CT) examination at another hospital. The patient underwent conventional ultrasound (US), contrast-enhanced ultrasound (CEUS), magnetic resonance imaging (MRI), 18F-fluorodeoxyglucose positron emission tomography/CT (PET/CT), and finally confirmed the diagnosis of SMARCA4-UT by US-guided puncture biopsy. After symptomatic management, the patient was transferred to another hospital and we performed a short-term follow-up. Conclusions: During this procedure, we obtained a series of relevant clinical and imaging data, especially US and CEUS images, which were described for the first time, offering valuable imaging information that will contribute to the clinical diagnosis of this disease to a certain extent. Moreover, this case highlights the efficacy of CEUS in identifying internal necrosis within tumors and lymph nodes, thereby improving the success rate of obtaining tumor tissue for pathological diagnosis. These findings substantiate the practical utility of US and CEUS in the context of mediastinal SMARCA4-UT, emphasizing their potential for widespread clinical adoption.