Rapid On-Site Evaluation has High Diagnostic Yield Differentiating Adenocarcinoma vs Squamous Cell Carcinoma of Non–Small Cell Lung Carcinoma, not Otherwise Specified Subgroup

Our objective was to evaluate the diagnostic yield of rapid on-site evaluation (ROSE) on the differential diagnosis of non–small cell lung carcinoma, not otherwise specified (NSCLC-NOS). Biopsied cases diagnosed as NSCLC-NOS with ROSE during 2004 through 2008 were retrieved. Diagnostic confirmation was done with immunohistochemistry (IHC) involving thyroid transcription factor-1 and p63 immunostains. For the study, 106 cases were available. The final diagnoses rendered were squamous cell carcinoma (SqCC) (n = 39) and adenocarcinoma (AC) (n = 67). Cytologic, histologic, and IHC concordance for these diagnoses occurred in 75 cases (70.8 %), of which 56 (52.8 %) were AC and 19 (17.9 %) were SqCC. Cytologic, histologic, and IHC discordance was found in 31 cases (29.2 %). Of these 31 cases, 11 NSCLC-NOS diagnoses histologically corresponded to 1 SqCC plus 4 ACs, and 4 favor SqCC plus 2 ACs; the former 5 NSCLC-NOS cases classified correctly through cytology, as well as IHC. However, IHC was not available for the latter 6 NSCLC-NOS cases that were also classified correctly through cytology. In addition, only 3 NSCLC-NOS diagnoses cytologically corresponded to 3 favor SqCC histologically, in which IHC was not available, and for 2 cases that both corresponded to favor SqCC and favor AC histologically and cytologically. In the other 15 cases, histology labeled 4 cases NSCLC-NOS and misclassified 2 cases; cytology labeled 1 case NSCLC-NOS and misclassified 13 cases. ROSE has high diagnostic yield over subclassification of NSCLC-NOS. We recommend allocating a cytotechnologist for specimen adequacy and a cytopathologist for cytologic diagnosis.