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

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 gamma 2 chain of laminin-5 and its proteolytic fragments comprise an invasion factor for many carcinomas. The aim of this study was to determine whether the immunocytochemical presentation of the laminin gamma 2 chain identifies pre-invasive or invasive squamous cells in brush biopsies. 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 gamma 2 chain: D4B5, 4G1, detection using ChemMate and Autostainer. 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 gamma 2 chain antibody (sensitivity of laminin gamma 2 chain immunocytochemistry, 93%). The positive predictive value was 100% for conventional cytology and 97% for laminin gamma 2 chain immunocytochemistry. The negative predictive value attained was 92% for conventional cytology and 97% for laminin gamma 2 chain immunocytochemistry. The high sensitivity level observed for method-enhanced brush cytology suggests that this technique be used as an initial diagnostic step.