Abstract
Background : T lymphoblastic lymphoma (T-LBL) frequently manifests with a mediastinal mass and pleural effusion. We report a case of early T-cell precursor lymphoblastic lymphoma (ETP-LBL) in which pleural fluid cytology showed more than 5% basophils in a background of atypical cells.
Case : A 14-year-old male patient with a past history of allergy presented with a prolonged history of cough and low-grade fever. A plain chest X-ray revealed pleural effusion and a mass lesion in the anterior mediastinum. Pleural fluid cytology showed atypical cells with fine granular chromatin, which led us to suspect a malignancy of lymphocytic origin. An increase in the number of basophils (7.3% of nucleated cells) was observed in the background. Immunohistochemical staining (IHC) of a pleural fluid cell block and mediastinal biopsy sections revealed atypical cells that showed positive staining for CD3 and CD99, and negative staining for CD4/CD8 and TdT. Bone marrow infiltration of less than 25% suggested the diagnosis of T-LBL. It was further classified as ETP-LBL because the atypical cells showed negative staining for CD1a and CD5, and weakly positive staining for CD117.
Conclusion : The differential diagnosis of lymphoma using IHC staining is crucial as determining the high-risk type of lymphoma is important for selecting the appropriate treatment. On the other hand, in our present case, the finding of basophilic pleural effusion was not directly related to the T-LBL diagnosis, and we considered the possibility of local infiltration of basophils associated with the tumor.
