CTICasesSMARCA4-Deficient Thoracic Carcinoma
Imaging findings
CTPA in a patient who arrived with a grave outside diagnosis shows that contrast injected through an upper extremity vein does not reach the right atrium and is diverted into extensive collateral vessels, so the study was repeated via a lower extremity vein. Imaging then reveals a very large mass involving the right atrium with SVC obstruction. Transvenous biopsy showed a poorly differentiated carcinoma that was nearly negative for most cell-surface markers except some cytokeratins, with rhabdoid cells described, in a smoker with a history of urothelial carcinoma.
Key takeaways
A very large, aggressive mediastinal or cardiac tumor causing SVC obstruction, with contrast diversion into collaterals, in a smoker, and a poorly differentiated carcinoma that is largely marker-negative with rhabdoid features should raise consideration of a SMARCA4-deficient thoracic carcinoma (as well as NUT carcinoma). These are aggressive non-small-cell tumors that can be confirmed by immunohistochemistry showing loss of the relevant protein, though confirmation was not pursued here because the patient died soon after.
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