Agarose cell block and ancillary molecular tests enhance diagnostic efficacy of liquid-based cytology samples

Background The concomitant use of cytology smears and cell block (CB) preparations for ancillary techniques represents a useful diagnostic performance, especially in suspicious malignant cases or with equivocal cytological morphology. CBs prepared by the agarose-based technique have a high morphologic quality. Agarose prevents notable loss of diagnostic cells during CB preparation. This can be used as a maximal investment for the residual supernatant liquid-based cytology (LBC) material. Aim To study the use of agarose CBs from residual LBC material as a diagnostic tool added to cytology smears in fluid and fine-needle aspiration cytology. Patients and methods The current study included 65 cases utilizing LBC slides, and agarose CBs prepared from the residual LBC material. Ancillary studies were performed on CBs using immunomarkers: CK-7, CK-20, ER, PR, CEA, calretinin, pan-cytokeratin, Her2, CK5/6, P63, TTF-1, HMB-45, and S-100, as well as chromogenic in-situ hybridization (CISH) Her2. Results The majority of our studied agarose CBs (89.2%) had morphologic criteria of the diagnostically superior category. Immunohistochemistry on agarose CBs raised the sensitivity from 85.3 to 100% in effusion cytology and from 92.9 to 100% in aspiration cytology. In this study, 60 out of 65 studied cases needed further diagnostic verification with consequent use of ancillary techniques on agarose CBs including immunohistochemistry and CISH. Regarding effusion cytology samples, immunomarkers enabled subtyping of 21 cases of metastatic adenocarcinoma (14 cases of noncolorectal origin and seven cases of metastatic colorectal adenocarcinoma). Moreover, verification of the origin of malignant cells in effusion cytology samples could be reached (mesothelioma was proved in 4/6 cases and disproved in two cases that were reported as metastatic adenocarcinoma). Moreover, the inconclusive cases of effusion cytology could be solved; 9/14 cases were confirmed as benign and the remaining five cases were reported as metastatic adenocarcinoma. In our study, two cases of metastatic breast carcinoma in pleural effusion were requested for hormonal profile (one showed positivity to ER, PR, and Her2 by immunocytochemistry and the other was triple negative, and Her2 negativity was confirmed by CISH performed on the agarose CB). In pulmonary specimens, immunohistochemical subtyping of nonsmall cell carcinoma cases was possible (6/8 cases were confirmed as squamous cell carcinoma, and the remaining two cases were adenocarcinomas). In the studied five cases of lymph node aspirates, the provisional broad diagnosis of metastatic undifferentiated malignancy could be further specified by immunohistochemical application of certain tumor markers; their choice was suggested according to morphologic criteria of LBC material. Of these five cases, there was one case of metastatic malignant melanoma. Another two cases were highly suggestive of thyroid origin. Unfortunately, two of these metastatic undifferentiated cases had diagnostically unsuitable CBs, and no further studies could be done. Four lymph node aspirates were inconclusive for metastasis and were reclassified by immunohistochemistry as three cases of reactive lymphadenopathy and one case of metastasis. Accordingly, final cytologic diagnosis could be achieved in 63 (97%) of our total 65 studied cases. The complementary use of agarose CBs helped in diagnosis of 54 (96.4%) of 56 cases that needed ancillary tests. Conclusion Agarose CBs prepared from LBC residues, together with cytology smears, can achieve significant and accurate results when coupled with different ancillary studies.