Fine needle aspiration biopsy of Ki-1-positive large-cell "anaplastic" lymphoma.

The cytopathologic, immunohistochemical and ultrastructural features of a case of Ki-1-positive lymphoma are presented and discussed. On fine needle aspiration (FNA) biopsy smears, the Ki-1-positive lymphoma was characterized by large isolated cells with abundant dense/vacuolated cytoplasm and large nuclei with irregular profiles. Although most cells contained one nucleus, binucleated and multilobed/multinucleated cells were also seen. The cohesion of the malignant cells in histologic sections of a biopsied lymph node suggested an anaplastic carcinoma. The discrepancy was resolved by ultrastructural and immunologic analyses. The main differential diagnoses on FNA material include Hodgkin's disease, malignant melanoma and undifferentiated carcinoma; the cytologic suspicion should be confirmed by immunocytochemical studies.