Diagnosis of T-cell lymphoma in body fluids: cytologic features and unusual flow cytometric findings

OBJECTIVE: To demonstrate the unique morphologic and phenotypic features observed in cases of T-cell lymphomas presenting as effusions. STUDY DESIGN: Cytologic slides and flow cytometric histograms of 8 cases of body fluids with T-cell lymphoma were retrospectively reviewed. Morphologic features, flow cytometric histograms and immunophenotypes of the cells were evaluated. RESULTS: Three of the 8 cases showed 1 or more of the following: intermediate-to-large cells with an increased nuclear-cytoplasmic ratio, finely granular or vacuolated cytoplasm and round or convoluted vesicular nuclei with a prominent single or multiple nucleoli. Flow cytometric studies of these 3 cases showed an abnormal scatter pattern in the myelomonocytic region of the histograms. Phenotypic analysis revealed variable expression of a T-cell phenotype. The remaining cases showed the conventional morphologic and flow cytometric features of a T-cell lymphoma. CONCLUSION: Morphologic alterations of neoplastic T-cells in body fluids can result in a variety of potentially incorrect diagnoses. The unusual flow cytometric histogram can serve as a useful clue for the diagnosis of T-cell lymphoma in body fluids but could be a potential pitfall for a false negative. Detailed cytologic evaluation combined with flow cytometric study can improve diagnostic accuracy.