Correlation of light microscopic, immunocytochemical and ultrastructural cytomorphology of anaplastic large cell Ki-1 lymphoma, an activated lymphocyte phenotype. A case report.

BACKGROUND: Anaplastic large cell Ki-1 lymphoma has been proposed to be a neoplasm of activated lymphocytes, mostly of T-cell origin. CASE: A previously healthy 12-year-old boy presented with a two-month history of a rapidly growing hard palate mass that involved the nasal cartilage and extended to the floor of the right orbit. By light microscopy (LM) the aspirates were very cellular, containing single, pleomorphic cells and occasional cellular aggregates. The cells showed distinct polarity, with the large, anaplastic nucleus at one end and the tapering cytoplasm, including a prominent paranuclear halo (or "hof"), at the other end ("hand mirror" appearance). The cytoplasmic border showed prominent ruffling, concentrated at the two poles of the cells and corresponding to the areas of the protopod and uropod. Immunocytochemically (ICC) the cells were positive for Ki-1, epithelial membrane antigen and UCHL-1, all of which showed both membrane positivity along with Golgi area staining. LCA showed variable membrane staining. Ultrastructurally (electron microscopy [EM]) the polarity was recapitulated, with an eccentric, horseshoe-shaped nucleus partially enclosing a prominent Golgi complex with associated centrosomes and asymmetric plasma membrane ruffling.
CONCLUSION: All three levels of examination (LM, ICC and EM) revealed tumor cell features corresponding to the phenotype of the activated lymphocyte. These features are characteristic, thus allowing the diagnosis of Ki-1 anaplastic lymphoma by fine needle aspiration cytology.