Abstract
Background : Thoracic SMARCA4-undifferentiated tumors are rare neoplasms that predominantly occur in adult males with a history of heavy smoking. These tumors manifest as large masses in the chest. Herein, we report a case in which the diagnosis was successfully made by pleural fluid cytology alone.
Case : An elderly man in his 80’s with a history of heavy smoking presented with a large tumor extending from the left pulmonary hilus to the mediastinum, along with left pleural effusion, as observed on chest CT. Cytological specimens and cell blocks were prepared from the pleural fluid. The cytological specimens revealed tumor cells that were isolated or in weakly cohesive clusters. The cytological specimen and cell block specimens stained with hematoxylin and eosin showed the presence of rhabdoid cells. Immunocytochemical staining demonstrated negative staining of the tumor cells for cytokeratin AE1/AE3, TTF-1, claudin-4, and E-cadherin in tumor cells. Expression of SMARCA4 and SMARCA2 were lost, while that of SMARCB1 was preserved. The tumor cells showed diffusely positive staining for CD34, and partial and sparsely positive staining for SOX2 and SALL4, respectively. Based on these findings, we established the diagnosis of thoracic SMARCA4-undifferentiated tumor.
Conclusion : Thoracic SMARCA4-undifferentiated tumors are highly aggressive. We demonstrated that these tumors can be diagnosed by pleural fluid cytology alone, which is especially useful, since it might be difficult to obtain tissue specimens from patients with this tumor.
