Immunoflow cytometry and cell block immunohistochemistry in the FNA diagnosis of lymphoma: a review of 73 consecutive cases

Aims-To review the results of 73 consecutive fine needle aspirations (FNAs) that were collected by a pathologist and analysed by immunoflow cytometry. Material for a cell block was also collected from some of these lesions. Methods-The setting was a large general hospital in rural New Zealand. The FNAs were performed by a pathologist, or a radiologist for image guided loc alisations. Material for immunoflow cytometry was collected into RPMI and, when required, material for a cell block was collected into formalin. Results-Of the 73 samples collected by FNA nine were inadequate. Light chai n restriction could be demonstrated in most FNA samples from B cell lymphom as (28 of 30 adequate samples). The exceptions were two cases of T cell ric h B cell lymphoma. Artefactual light chain restriction was seen occasionall y in T cell lymphomas, presumably as a result of autoantibodies binding to the cell surfaces. It was possible to subtype most (18 of 30 adequate sampl es) B cell lymphomas as chronic lymphocytic leukaemia (CLL), follicle centr e cell lymphoma (FCCL), or mantle cell lymphoma. The CD4 to CD8 ratio was n ot usually restricted in T cell lymphomas and coexpression of CD4 and CD8 w as not usually found. Loss of pan-T cell antigens was seen in some T cell l ymphomas. Four of the six T cell. lymphomas and three of the four non-lymph oid malignancies were diagnosed with the aid of cell block immunohistochemi stry. Only one of the four cases of Hodgkin's lymphoma showed Reed-Sternber g cells in the FNA smears. Conclusions-It is not always possible to characterise lymphomas as fully wi th FNA and immunoflow cytometry as is possible with biopsy histology and a full battery of modern investigations. Nevertheless, in the setting of a la rge rural general hospital immunoflow cytometry on FNA samples is a highly effective method of diagnosing and typing B cell lymphomas. Immunoflow cyto metry is of little use for T cell lymphomas or Hodgkin's lymphomas. We advo cate the use of cell block immunohistochemistry in preference to immunoflow cytometry for cases in which the cytological appearance of the specimen is overtly malignant but the differential diagnosis includes nonlymphoid mali gnancy.