Occult neuroendocrine differentiation in non-small cell lung carcinoma

Introduction: Neuroendocrine (NE) differentiation can be documented by immunohistochemistry (IHC) with the use of synaptophysin (SYN) and chromogranin (CGA) in some lung carcinomas with conventional non-small cell morphology. These tumors are referred as non-small cell lung carcinomas with neuroendocrine differentiation (NSCLC-ND) or non-small cell lung carcinoma with occult neuroendocrine differentiation. The finding of NE differentiation in some NSCLC has led to the hypothesis that these tumors may form a subgroup with a prognosis and response to treatment between NSCLC and SCLC. (Pelosi et al., 2003; Wick et al., 2011; Howe et al., 2005) Aim: To find occult NE differentiation in NSCLC using CGA and SYN. Materials and Methods: The IHC markers, CGA and SYN were done on 37 NSCLC cases which compromised of 23 Squamous cell carcinomas (SCC) and 14 adenocarcinomas. Semiquantitative assessments of staining intensity and percentage of tumour cells positive were made. An Intensity Distribution (ID) score of > 1 with any marker was used as the criterion for evidenceof NE differentiation. Results: NE differentiation was seen in 40.54% of NSCLC. 50% of adenocarcinomas and 34.8% SCC showed NE differentiation. SYN and CGA positivity was seen in 29.7% and 24% NSCLCs respectively. Adenocarcinoma showed significant immunoreactivity for SYN (p=0.042) while SCC showed significant immunoreactivity for CGA (p=0.035) Conclusion: In our study, 40.5% of NSCLC showed NE differentiation. NE differentiation was seen more in adenocarcinoma than in SCC. Synaptophysin showed significant association with adenocarcinomas and chromogranin with SCC.