SMARCA4-deficient thoracic tumor detected by [18F]FDG PET/CT

Thoracic SMARCA4-Deficient Undifferentiated Tumor Mimicking Malignant Pleural Mesothelioma on FDG PET/CT

ABSTRACT

We describe contrast-enhanced CT and FDG PET/CT findings in a case of thoracic SMARCA4-deficient undifferentiated tumor with extensive pleural involvement and mediastinal lymph node metastases. Contrast-enhanced CT showed multiple enhancing right-sided pleural masses and soft tissue plaques and enlarged mediastinal lymph nodes. The pleural lesions and mediastinal lymph nodes showed intense FDG uptake mimicking malignant pleural mesothelioma with mediastinal lymph node metastases.

Thoracic SMARCA4-Deficient Undifferentiated Tumor Mimicking a Pleural Mesothelioma on 18 F-FDG PET/CT

ABSTRACT

A 72-year-old woman, who was a nonsmoker, presented with chest distress persisting for over 10 days. Plain chest CT revealed thickening of the left pleura accompanied by hydrothorax. Subsequent 18 F-FDG PET/CT showed irregular thickening involving the visceral, parietal, and interlobular pleura on the left side, with diffuse high avidity of 18 F-FDG. The left pleural mesothelioma was suspected initially, but pathological examination from biopsied specimen later confirmed a thoracic SMARCA4-deficient undifferentiated tumor.

Occult SMARCA4-Deficient Undifferentiated Carcinoma Unmasked by 68 Ga-FAPI-46 PET/CT

ABSTRACT

SMARCA4-deficient undifferentiated tumors (SMARCA4-dUT) are rare and aggressive neoplasms commonly found in male smokers and portend a poor prognosis. In this case, we reported 18 F-FDG and 68 Ga-FAPI-46 PET/CT findings in an occult SMARCA4-dUT located in the left pulmonary hilum along with mediastinal lymph node metastases. 68 Ga-FAPI-46 PET/CT showed superiority over 18 F-FDG for detecting SMARCA4-dUT lesions. This case highlighted that 68 Ga-FAPI-46 PET/CT may be a promising imaging modality in the evaluation of SMARCA4-dUT, particularly for detecting the occult SMARCA4-dUT arising in uncommon sites.

SMARCA4-deficient tumors in the adrenal gland and small intestines: A rare case report

Thoracic SMARCA4-deficient undifferentiated tumors (SMARCA4-UTs) are rare undifferentiated thoracic malignancies with poor prognosis. They predominantly affect young men who are heavy smokers. Recently, the category of SMARCA4-deficiency-related malignancy has been expanded to include extra-thoracic sites, such as the paranasal sinuses, gastrointestinal tract, ovary, and uterus. We report a rare case of SMARCA4-deficient tumors in the adrenal gland and small intestines. SMARCA4-deficient tumors should be included in the differential diagnosis when multiple large masses with heterogeneous contrast effect and strong accumulation are seen in cancers of unknown primary on 18F-fluorodeoxyglucose (FDG) positron emission tomography with computed tomography (PET/CT).

68 Ga-DOTA-FAPI-04 PET/CT in the Detection of Thoracic SMARCA4-Deficient Undifferentiated Tumor

ABSTRACT

Thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a rare malignant disease. We present the case of a 56-year-old woman with thoracic SMARCA4-UT presenting as a mediastinal mass who underwent 68 Ga-DOTA-FAPI-04 PET/CT imaging. Intense 68 Ga-DOTA-FAPI-04 uptake was observed in the primary tumor and lymph node metastases. After 7 cycles of immune checkpoint inhibitor plus chemotherapy, the patient underwent mediastinal mass resection, and postoperative pathology confirmed a complete pathologic response. This case may provide valuable insights into the diagnosis and monitoring of the treatment response of thoracic SMARCA4-UT.

FDG PET/CT in a Case of Thoracic SMARCA4-Deficient Undifferentiated Tumor

ABSTRACT

Thoracic SMARCA4-deficient undifferentiated tumor is a rare, newly recognized poorly differentiated tumor with poor prognosis. FDG PET/CT findings of thoracic SMARCA4-deficient undifferentiated tumor are rarely reported. We describe FDG PET/CT findings in a case of thoracic SMARCA4-deficient undifferentiated tumor. The tumor presented as a pleural mass, destroyed the adjacent ribs, and showed intense FDG uptake with SUV max of 12.7. This case indicates that thoracic SMARCA4-deficient undifferentiated tumor should be included in the differential diagnosis of FDG-avid pleural lesions.

Molecular, clinicopathological characteristics and surgical results of resectable SMARCA4-deficient thoracic tumors

PURPOSE

SMARCA4-deficient thoracic tumors are rapid aggressive malignancies, often diagnosed at an advanced and inoperable stage. The value of pulmonary resection for resectable SMARCA4-deficient thoracic tumors is largely unknown.

METHODS

In this observational study, we included 45 patients who received surgery for stage I-III SMARCA4-deficient tumors. We compared the molecular, clinicopathological characteristics and survival between SMARCA4-dNSCLC and SMARCA4-deficient undifferentiated tumor (SMARCA4-dUT) patients.

RESULTS

Thirty-four SMARCA4-dNSCLC and 11 SMARCA4-dUT patients were included in this study. Molecular profiles were available in 33 out of 45 patients. The most common mutated gene was TP53 (21, 64%), and followed by STK11 (9, 27%), KRAS (5, 15%), FGFR1 (4, 12%) and ROS1 (4, 12%). There were 3 patients that harbored ALK mutation including 1 EML4-ALK rearrangement. There were 2 patients that harbored EGFR rare site missense mutation. SMARCA4-dUT patients had significance worse TTP (HR = 4.35 95% CI 1.77-10.71, p = 0.001) and OS (HR = 4.27, 95% CI 1.12-16.35, p = 0.022) compared to SMARCA4-dNSCLC patients. SMARCA4-dUT histologic type, stage II/III, R1/2 resection and lymphovascular invasion were independent poor prognostic predictors for both TTP and OS. There were 8 patients who received immunotherapy, the objective response rate was 50%. The SMARCA4-dNSCLC patient with ALK rearrangement was treated with crizotinib as second-line therapy, and achieved stable disease for 9.7 months.

CONCLUSION

Patients with SMARCA4-deficient tumors have a high probability of early recurrence after surgery, except for stage I patients. Immunotherapy seems to be a valuable strategy to treat recurrence.