Mediastinal teratoma as a cause of pleural effusion

INTRODUCTION: Teratomas are congenital tumors originating from pluripotent germ cells that contain derivatives of the three germ layers. One of their extragonadal forms is the anterior mediastinum, where they can present atypically. CLINICAL CASE: A 3-year-old female patient was diagnosed with a cystic mediastinal teratoma in the context of pleural effusion due to tumor rupture. With negative tumor markers, surgical resolution was performed, which evidenced a heterogeneous tumor, adhered to adjacent structures, that was completely resected. The histopathology was compatible with a mature teratoma presenting pancreatic tissue, whose enzymatic secretion we assume was responsible for its rupture. CONCLUSIONS: Cystic mediastinal teratomas can rupture and present as pleural effusion. Although this form of presentation is unusual, it is necessary to be aware of it for proper medical and surgical management.