Histopathologic Characteristics of Pulmonary Adenocarcinomas with and without EGFR Mutation
Chavit Chantranuwat MD*, Virote Sriuranpong MD, PhD**, Nusara Huapai BSc***, Thep Chalermchai MD**, Kittichai Leungtaweeboon MD****, Narin Voravud MD**, Apiwat Mutirangura MD, PhD***
Affiliation : * Department of Pathology, King Chulalongkorn Memorial Hospital University ** Medical Oncology Unit, Department of Medicine, King Chulalongkorn Memorial Hospital University *** Genetic Unit, Department of Anatomy, King Chulalongkorn Memorial Hospital University **** Department of Surgery, King Chulalongkorn Memorial Hospital University
EGFR mutation played crucial role for responsiveness of non-small cell lung cancers to EGFR
tyrosine kinase inhibitors. Almost the mutations were present in adenocarcinomas. Few had studied on
histopathologic correlation with EGFR mutation in pulmonary adenocarcinomas. To obtain better view on
pathobiology of pulmonary adenocarcinomas, we correlated exons 19 and 21 mutations with various histo-
pathologic features by dissecting particular histological patterns from 60 surgically resected adenocarcino-
mas.
Results : Gland-forming pattern, including bronchiloloalveolar carcinoma (BAC), well-formed acinar,
and poorly-formed acinar patterns more frequently contains EGFR mutations than solid pattern (72.7% vs.
23.1%, p=0.002). EGFR mutations of each within the gland-forming pattern are not significantly different.
Micropapillary pattern revealed less exon 19 mutations than the gland-forming pattern (12.5% vs. 66.7%,
p=0.018), but tended to have more Exon 21 mutations than the others (33.3% vs. 11.9%, p=0.10). Tumors
predominated by BAC pattern more commonly had exon 19 mutations than non-BAC predominated tumors
(68.8% vs. 39.5%, p=0.046). EGFR-mutated tumors comprised less proportion of papillary pattern than
tumors without mutation (mean=1.5% vs. 11.2%, p=0.049). Terminal respiratory unit (TRU) histology was
associated with more EGFR mutations (72.4% vs. 42.1%, p= 0.036). Tumors smaller than 3.5 cm had more
EGFR mutations than larger tumors (73.1% vs. 41.9%, p=0.018).
Conclusion : High frequency of the mutation
does not present only in BAC pattern, but also in well-formed and poorly-formed acinar patterns, suggesting
them as usual spectrum of EGFR mutated adenocarcinomas. Other characteristics of EGFR-mutated adeno-
carcinomas include TRU-type histology, smaller size, and less solid phenotype.
Keywords : Lung, Adenocarcinoma, Histopathology, EGFR mutation
