P3.01-016 Factors Influencing the Concordance of Histological Subtype Diagnosis by Biopsy and Resected Specimens of Lung Adenocarcinoma: Topic: Morphology

Abstract

Lung adenocarcinoma is heterogeneous, characterized by various histological subtypes. Determination of the predominant histological subtype (lepidic, papillary, acinar or solid-predominant) has been shown to correlate with genetic abnormalities and clinicopathological features. Although subtyping using small biopsy samples is important for tailored approaches to clinical management, limited data exist on the concordance of predominant subtype between resected specimens and biopsy specimens. We compared the diagnosed predominant subtypes in resected specimens and matched biopsy specimens in a series of 327 lung adenocarcinomas. Histological subtyping of preoperative material was made by review of archived hematoxylin and eosin stain slides that had originally been prepared for diagnosis before surgery. The histological subtype of surgically resected tumors was obtained from the pathological case records for each surgical resection specimen. The accuracy of preoperative diagnosis by biopsy and the factors that influence concordance with resected specimen analysis were examined. In 211 of the 326 patients (66.0%), the predominant adenocarcinoma subtype diagnosed from biopsy matched the findings of resection analysis. Concordance rate was highest in papillary pattern (82%), followed by lepidic pattern (75%), solid pattern (66%), and acinar pattern (39%). Overall, the concordance rate in biopsy samples with larger tumor areas (≥0.7 mm2) was significantly higher than in those with smaller tumor area (<0.7 mm2; 71% vs 58%, respectively; p = 0.02). Other factors in biopsy samples, such as number of biopsies, or the small biopsy type, did not have significant influence on the concordance between preoperative and postoperative diagnosis. In the biopsy samples with smaller tumor areas, the concordance rate was 77% in lepidic subtype, 71% in papillary subtype, 60% in solid subtype, and 40% in acinar subtype. Concordance rate in the biopsy samples with larger tumor area was higher in papillary and solid subtypes (88% and 76%, respectively), but remained low in acinar subtype (37%). These results indicate that accuracy of adenocarcinoma subtyping based on small biopsy samples is influenced by tumor area. Our study also suggests that subtyping of acinar histology using biopsy specimen is particularly error-prone.