Laminin‐5 immunocytochemistry: a new tool for identifying dysplastic cells in oral brush biopsies

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Abstract
Background:  The brush biopsy technique is not only a seminal technique but also a critically discussed method for detection of oral pre‐cancerous stages and manifest carcinomas. The γ2 chain of laminin‐5 and its proteolytic fragments comprise an invasion factor for many carcinomas.Objectives:  The aim of this study was to determine whether the immunocytochemical presentation of the laminin γ2 chain identifies pre‐invasive or invasive squamous cells in brush biopsies.Methods:  The value‐based identification of atypical epithelia was analysed in 93 consecutive brush biopsies with histopathological diagnoses: standardized haematoxylin and eosin staining; standardized immunocytochemistry: monoclonal antibodies against laminin γ2 chain: D4B5, 4G1, detection using ChemMate and Autostainer.Results:  Conventional cytology did not result in any false‐positive cases, i.e. atypical cells in normal, inflamed or benignly hyperproliferative mucosa (specificity, 100%), whereas immunocytochemistry revealed one false‐positive case (specificity, 98%). In brush biopsies of oral squamous cell carcinomas, the following immunocytochemical patterns were possible: (1) staining of the cytoplasm, (2) banded markings between clumped carcinoma cells and (3) positive hazes surrounding atypical cells. Bacterial colonies appeared as false‐positive results. Four of 27 carcinomas and one of three recurrences were not cytologically identified (sensitivity of conventional cytology, 79%). Three of the five carcinomas not identified by cytology were immunocytochemically stained with laminin γ2 chain antibody (sensitivity of laminin γ2 chain immunocytochemistry, 93%). The positive predictive value was 100% for conventional cytology and 97% for laminin γ2 chain immunocytochemistry. The negative predictive value attained was 92% for conventional cytology and 97% for laminin γ2 chain immunocytochemistry.Conclusions:  The high sensitivity level observed for method‐enhanced brush cytology suggests that this technique be used as an initial diagnostic step.