Immunocytochemical staining for stratifin and OCIAD2 in bronchial washing specimens increases sensitivity for diagnosis of lung cancer.

OBJECTIVE Brushing or washing cytology taken at bronchoscopy is a standard diagnostic procedure for lung cancer. The present study evaluated the sensitivity of immunocytochemical diagnosis of lung cancer using bronchial washing materials. METHODS We collected bronchial washing samples taken at bronchoscopy between July 2012 and July 2013 at Tsukuba University Hospital and studied 106 cases that were finally diagnosed as lung cancer. We collected exfoliated cells using a thin-layer advanced cytology assay system (TACAS(™)) and performed cytological diagnosis using Papanicolaou staining. As controls, we randomly selected 30 tumour-negative cases from among samples collected during the same period. Using these materials, we also examined the expression of stratifin (14-3-3 sigma) (n = 92) and OCIAD2 ovarian immunoreactive antigen domain 2) (n = 106) by immunocytochemistry, as these are considered to be broad spectrum immune markers for lung adenocarcinoma including early invasive lung adenocarcinoma. RESULTS Using Papanicolaou staining, 52 out of 106 lung cancers (49.1%) were diagnosed as positive. However, positivity was increased to 63.0% by immunocytochemistry using anti-stratifin or anti-OCIAD2 antibodies. Biopsies were taken in 103/106 cases and cancer was diagnosed in 60/103, (58.3%). The sensitivity of stratifin or OCIAD2 was significantly higher than that of Papanicolaou staining (P = 0.027), but immunocytochemistry detected false-positive cells in 3/30 cases (10%) for stratifin and 2/30 cases (7%) for OCIAD2. CONCLUSION Immunocytochemical staining for stratifin and OCIAD2 improved diagnostic sensitivity for lung cancers but diagnostic specificity was lower than that for cytology alone. The immunostains carried up to a 10% risk of a false-positive result and therefore positive staining must be confirmed by morphological evidence of malignancy.