The histologic heterogeneity of lung adenocarcinoma is well known. Many histologic subtypes have been described, and recently their prognostic and predictive value has emerged. Laser capture microdissection may aid in the isolation of cancer cells from distinct subtypes of lung adenocarcinoma, thus enabling the description of their specific molecular features. Characterization of epidermal growth factor receptor (EGFR) mutations in histologic subtypes of lung adenocarcinoma has become an important issue. The purpose of this study was to analyze EGFR mutations in exons 18-21 in single histologic subtypes of lung adenocarcinoma after laser capture microdissection. A revision and reclassification of a series of 208 non-small cell lung cancers was conducted, and 62 adenocarcinomas with a total of 119 histologic component subtypes were identified. Laser capture microdissection of each subtype was performed. EGFR mutations in exons 18-21 were detected using polymerase chain reaction single-strand conformation polymorphism and direct DNA sequencing. EGFR mutations were detected only in 3 out of the 62 adenocarcinomas analyzed. Two adenocarcinomas harbored EGFR mutations in exon 19 (the E746-T751 deletion VA insertion and the LREAT deletion) and one adenocarcinoma the EGFR exon 21 L858R missense point mutation. EGFR mutations were observed in all component subtypes. This suggests that, in a patient with lung adenocarcinoma, EGFR mutations are not associated with particular component histologic subtypes and probably occur at an early stage of tumorigenesis. Notably, 2 out of the 3 mutated adenocarcinomas had a bronchioloalveolar component, whereas the third mutated adenocarcinoma had a papillary subtype. Although we detected EGFR mutations only in 3 out of 62 adenocarcinomas and EGFR mutations were present in every subtype of each mutated adenocarcinoma, our research might represent a basis for further studies in characterizing molecular profiles of different component subtypes of lung adenocarcinoma.

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