Fine needle aspiration cytology, histology and immunohistochemistry of anaplastic large cell Ki-1-positive lymphoma. A report of three cases.
BACKGROUND: Large cell anaplastic Ki-1 lymphoma is a cytologically undifferentiated malignant lymphoma that needs to be distinguished from a variety of other neoplasms using immunohistochemistry. CASES: The cytopathologic, histopathologic and immunohistochemical features of three cases of Ki-1-positive anaplastic large cell lymphoma are presented. The patients comprised two females and one male, ranging in age from 48 to 82 years. Presentation was with peripheral lymphadenopathy. Fine needle aspiration biopsy of an enlarged lymph node in each case revealed single cells and poorly cohesive groups of cells with large, pleomorphic nuclei, many containing prominent nucleoli, and a moderate amount of cytoplasm. Many binucleate and multinucleate tumor cells were present. In each case the cytologic features suggested metastatic anaplastic carcinoma. The histopathologic features of excised nodes were also suggestive of this diagnosis, with cohesive groups of cells and many multinucleate tumor giant cells. In one case malignant cells were confined to subcapsular and medullary sinuses, further highlighting the resemblance to metastatic carcinoma. Immunohistochemical staining of histologic sections confirmed the diagnosis of large cell anaplastic, Ki-1-positive lymphoma, with the tumor cells in the three cases showing diffuse and strong positive staining for Ki-1 antigen. Further immunohistochemistry revealed tumor cells in two cases to be positive for leukocyte common antigen, two cases to express B-cell markers and one case to express T-cell markers. CONCLUSION: The fine needle aspiration biopsy findings confirmed that large cell anaplastic, Ki-1-positive lymphoma should be considered in the cytologic differential diagnosis of anaplastic tumor within a lymph node. The differential diagnosis may include anaplastic carcinoma, malignant melanoma, sarcoma, Hodgkin's disease and histiocytic lymphoma. Immunostaining of fine needle aspiration biopsy material or, preferably, of histologic tissue sections is necessary for confirmation of the diagnosis.