DNA Ploidy Analysis and Cell Block Immunohistochemistry in the Diagnosis of Malignant Effusions

Effusion cytology is a major diagnostic tool in medicine and has both therapeutic and prognostic implications. One of the dilemmas encountered is the differentiation between atypical cells and reactive mesothelial cells. The use of ancillary tools can reduce this grey zone and help to achieve a definitive diagnosis.

The main objective of this study was to evaluate the role of flow cytometry (FCM) and cell block with immunohistochemistry (IHC), along with the clinicoradiological investigations, to achieve a final diagnosis in effusion cytology to the maximum extent possible.

A prospective study was conducted. Effusion fluids, showing adequate amount and cellularity, were processed for conventional cytology, ploidy analysis by FCM, and cell block analysis, followed by IHC wherever required. Conventional cytological analysis was done by 2 independent pathologists, to look for interobserver variation, if any. The final result was achieved on the basis of integration of the results of the aforementioned studies, cytological details, clinicoradiological information, tissue biopsy findings, and follow-up.

A total of 90 samples were analyzed. On cytological examination, observer I categorized 60% samples as benign and 18.8% (n = 17) as malignant versus 58% categorized as benign and 23.3% (n = 21) as malignant by observer II. Observer I reported 19 (21.1%) equivocal cases and observer II reported 16 (17.7%). When both pathologists were considered together, the number of equivocal cases increased to 20. Sensitivity and specificity of FCM were 96.67 and 100%, respectively, and 100% for the cell block. On combining all techniques, the equivocal cases were resolved and a total of 33 cases were reported as malignant. However, 3 cases could still not be categorized and were labeled inconclusive.

Conventional cytology combined with cell block IHC and FCM has the potential to minimize the requirement of tissue biopsy for confirmation. If the first sample is used judiciously for all the techniques, this may reduce the requirement for a second sample and possibly also the time required for a definite diagnosis and the initiation of therapy.