Pasathorn Potivongsajarn1 M.D., Shanop Shuangshoti1 M.D., Poonchavist Chantranuwatana1 M.D.
1Department of Pathology, King Chulalongkorn Memorial Hospital University, Bangkok, Thailand
Objective: The 2011 international association for the study of lung cancer/ American thoracic society/ European respiratory society (IASLC/ATS/ERS ) classiﬁ cation changed the approach for deﬁ nite histologic diagnosis of lung cancer. The objective of this article is to describe the impact of the 2011 IASLC/ATS/ERS classiﬁ cation on small biopsy diagnosis of primary lung cancer in King Chulalongkorn Memorial (KCM) Hospital during the period of 2012 to 2014.
Materials and Methods: 383 lung biopsies of primary lung cancers were recruited from the surgical pathology database in KCM Hospital from 2012 to 2014. Data on H&E diagnosis, diagnosis after immunohistochemical study (IHC), and molecular studies of EGFR and ALK gene were obtained.
Results: H&E diagnosis of speciﬁ c tumor subtype could be achieved in 250 (65%) of the biopsies. The vast majority were non-small cell carcinomas (NSCC) composed of 202 (80.8%) adenocarcinomas (ADCA) and 41 (16.4%) squamous cell carcinomas (SQCA). Of 105 H&E unresolved biopsies with available IHC study, 81 (77.1%) could be resolved by IHC study including 51 (48.5%) adenocarcinomas, 10 (9.5%) squamous cell carcinomas, 13 (12.4%) small cell carcinomas, 4 (3.8%) lymphomas, 2 (1.9%) sarcomatoid carcinomas and 1 (0.9%) lymphoepithelial carcinoma. 24 (22.9%) IHC unresolved cases included 18 (17.1%) “NSCC, NOS”, 2 (1.9%) “NSCC, NOS, IHC could represent adenosquamous carcinoma”, 1(1%) “combined small cell carcinoma and NSCC, NOS”, 2 (1.9%) “sarcoma, NOS” and 1 (1%) “NSCC vs small cell carcinoma”. The two most common factors limiting H&E diagnosis were “few tumor cells” (9.9%) and “needle aspiration” (9.1%) with lower H&E resolution rate of 28.9% and 31.4%, respectively. However, the resolution rates after IHC study were still high (90.9% and 70%, respectively). EGFR mutation was detected in 31 of 45 cases (68.9%). Most of the tests were performed on H&E resolved adenocarcinomas (36 cases). Mutually exclusive positive results of ALK study was noted in 4 of 33 cases (12.1%). 4- antibody panels (TTF-1, CK7, p63, CK5/6) were available in 59 H&E unresolved NSCCs. Discrepancy between interpretation of 2 (TTF-1, p63) and 4 antibodies existed in 17 cases (28.8%). 5 “NSCC, favor SQCA” diagnosed by 2 antibodies were “NSCC, NOS” by 4 antibodies. 12 “NSCC, NOS” diagnosed by 2 antibodies were “NSCC, favor ADCA” by 4 antibodies.
Conclusion: The 2011 IASLC/ATS/ERS diagnostic algorithm has improved tumor subtype diagnosis of H&E unresolved NSCCs (75% IHC resolution rate). For H&E unresolved NSCC, 4-antibody panel is preferred to 2-antibody panel, since the latter could mislead the molecular study in some cases. Although various factors can limit the H&E resolution rate, the resolution rate after IHC study is still high. The relatively high
Abstracts in Th e 27 th Annual Meeting of the Royal Colllege of Pathologists of Th ailand “ Stronger Together by Quality” during 24 th -26 th February, 2016 at Ambassador Hotel, Bangkok, Th ailand. 37 incidence of EGFR mutation is likely due to a high proportion of H&E resolved adenocarcinoma which had better differentiation. A high rate of ALK gene rearrangement was noted and should be validated further by a study among a larger subset of the Thai population.