Abstract 4209: Genotypic agreement between histological specimen and preoperative cytology in small lung adenocarcinoma.

Abstract

Abstract Background. Histological subtype and genotype is critical for making treatment decisions and improving patient outcomes in non-small cell lung cancer (NSCLC). Approximately 70% of lung cancers are diagnosed in advanced stages where small biopsies and cytological specimens are the only source of material for both diagnosis and genotyping. Patients with specific gene alterations in epidermal growth factor receptor (EGFR) or anaplastic lymphoma kinase (ALK) likely receive more benefit from EGFR TKI or ALK TKI therapy, respectively. Although, genotyping agreement from cytological and histological samples is critical, more investigational studies need to be explored to assess the concordance of genotype. Purpose. We performed a comparing investigation on concordance rate for pathological diagnosis and EGFR gene mutation status between surgical specimen and preoperative cytological specimen in small lung cancer. Additionally we reviewed immunohistochemical (IHC) staining with two different ALK specific antibodies. Materials and Methods. 55 patients who had surgically resected small (≦3cm) lung adenocarcinoma with known preoperative bronchial brushing cytology were examined retrospectively. IHC staining was conducted by mutation-specific antibodies using E746-A750 deletion and L858R for EGFR or 5A4 and D5F3 for ALK. DNA analysis was performed by PNA-RNA PCR clamp assay. Results. 1) Diagnostic concordance rate between cytological and histological specimen was 90.9%. Disagreement cases were included one case of squamous cell carcinoma, two cases of small cell carcinoma, one case of melanoma and one case of mucoepidermoid carcinoma by cytology. 2) In IHC positive for mutation-specific EGFR antibodies, the sensitivity was 83% in E746-A750 and 100% in L858R, respectively. In EGFR IHC positive cases, well to moderate differentiation were dominant. 3) In ALK IHC, one case was observed stronger cytoplasmic staining in D5F3 than 5A4. Furthermore, the cribriform pattern was observed in H&E staining. Distinctive cytological feature was not observed. Conclusion. Our results showed that high genotype concordance rates of histology and cytology agreement in small lung adenocarcinoma. Citation Format: Noriko Hirai, Sasaki Takaaki, Yoshinori Minami, Masahiro Kitada, Naoyuki Miyokawa, Yoshinobu Ohsaki. Genotypic agreement between histological specimen and preoperative cytology in small lung adenocarcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4209. doi:10.1158/1538-7445.AM2013-4209