Background and aims: Molecular testing for epidermal growth factor receptor (EGFR) mutations has recently become a standard practice for the management of patients with non-squamous none small cell lung cancer. Primary small intestine adenocarcinoma (SIA) is an uncommon malignancy, and EGFR mutation in the cancer has not been well characterized due to its rarity.
Methods: A micro-tissue array with 53 SIAs and 24 surgically resected primary non-ampullary SIAs were studied. EGFR mutations were analyzed by DNA sequencing in 24 cases with formalin-fixed paraffin-embedded blocks. All 77 cases were examined by immunohistochemistry (IHC) using antibodies specific for the EGFR E746-A750 deletion in exon 19 (DEL), L858R point mutation in exon 21 (L858R), and total EGFR. EGFR amplifications were detected by fluorescence in situ hybridization.
Results: A positive reaction of DEL-specific, L858R-specific, and total EGFR antibodies was detected in seven (9.1%), 5 (6.5%) and 35 (45.5%) of 77 SIAs by IHC, respectively. Positive reaction of the three antibodies was not significantly correlated with patient's age, gender, differentiation, and stage. EGFR gene amplification was assayed in 77 SIAs in micro-tissue array. Of 24 SIA samples that had DNA sequencing, two (8.3%) harbored exon 19 deletion and one (4.2%) harbored L858R point mutation. Only one case with EGFR amplification and two cases with polysomy were shown.
Conclusions: Our findings suggested that mutations and amplification in EGFR genes are minor events, and most of SIAs may be unsuitable to EGFR-TKIs treatment.