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.