RESUMEN
Ki-1 positive anaplastic large cell lymphoma is a newly described high-grade lymphoma and is defined by histopathological and immunologic criteria. We experienced a case of systemically involving Ki-1 positive anaplastic large cell lymphoma in a 44 year- old female which initially manifested as pleural effusion. Abdominopelvic CT scan showed the evidence of marked lymphadenopathy in retroperitoneal and both external and inguinal lymph nodes. On cytologic examination of pleural fluid, tumor cells revealed pleomorphic large isolated cells with prominent nucleoli and abundant cytoplasms. The nuclei were large with irregular profiles including some deep invaginations. Also, occasional multilobed/ multinucleated and binucleated nuclei were seen. Immunohistochemical examination was performed to differentiate from the undifferentiated adenocarcinoma, Hodgkin's disease, non-Hodgkin's lymphoma and malignant histiocytosis. The neoplastic cells were positive for leukocyte common antigen, CD3, CD30(Ki-1) but negative for cytokeratin, epithelial membrane antigen, and CD15. A histologic diagnosis of Ki-1 positive anaplastic lymphoma was made by biopsies of the inguinal lymph node, polypoid lesions of the stomach and cecum.