Destaining hematoxylin and eosin stains and restaining for immunohistochemistry has diagnostic value for cytology samples

Objectives: The use of one antibody per slide for immunohistochemical (IHC) studies is difficult to interpret when neoplastic cells are sparse, mixed with complex mixtures of other cells, or are obscured by the IHC stain itself. To accurately assign IHC results to particular neoplastic cells, we developed and validated a technique of destaining hematoxylin and eosin (H&E) stains and restaining (DSRS) by IHC on cytology cell block sections and studied its utility. Materials and Methods: We identified 9 patients with fine needle aspiration (FNA) samples performed for a variety of tumors. Specimens were collected and made into ThinPreps and cell blocks. Cell block serial H&E stains revealed a rich background of benign cells, with rare scattered atypical cells arranged singly or in small clusters. Select H&E slides were scanned, destained, and then restained with one IHC biomarker per H&E. Slide scanning and image synchronization were used in tracking neoplastic cells. IHC results were validated for the DSRS process for all antibodies without the need for modification of the IHC protocol. Diagnoses rendered on the limited FNA samples were compared with those made on core biopsies, resections, or cytologic samples with ample cell quantity. Results: DSRS of the limited FNA samples did not compromise the quality of tissues or IHC, and comparison of the limited FNA diagnosis and final diagnosis rendered on more adequate specimens revealed concordant and accurate diagnosis in 89% (8/9) of cases, in contrast to a concordance rate of 22% (2/9) before the use of DSRS while the immunostain interpretation accuracy rate is 100% (9/9). Conclusion: DSRS of cytology cell block sections allows IHC stains to be ascribed to particular cells, enabling diagnosis when material is sparse, when diagnostic cells are admixed with other cell types, and when the IHC stain itself would otherwise obscure the identity of cells. DSRS provides an inexpensive alternative to other, more advanced techniques such as multiplex IHC or immunofluorescence.