Undiagnosed retroperitoneal mass. Report of a case in which needle aspiration cytodiagnosis led to investigation and timely management.

Needle aspiration cytology of an undiagnosed retroperitoneal mass was performed on a 37-year-old male. The cytologic findings were highly consistent with a seminoma. In the differential diagnosis the possibility of non-Hodgkin's lymphoma, melanocarcinoma and metastatic adenocarcinoma was considered. The cytologic features in the aspirate included uniform, single to loose groups of malignant cells with round nuclei and prominent nucleoli and pale cytoplasm with occasional vacuoles. A variable number of lymphocytes were intermingled with the neoplastic cells. On immunostaining, the markers for lymphoma, melanoma and epithelial malignancy were negative, while alpha-1-antitrypsin was positive in malignant cells, and alkaline phosphatase activity was weakly positive in the cytoplasm. In view of the cytologic diagnosis, a clinical examination of the testes was undertaken and followed by an ultrasound examination, which demonstrated a well-demarcated tumor in the left testis. It was removed and diagnosed as a typical seminoma. This case is of interest since needle aspiration cytodiagnosis not only suggested the correct diagnosis in an otherwise-undiagnosed retroperitoneal mass but also led to a timely investigation and correct management.