Prognostic value of complex glandular patterns in invasive pulmonary adenocarcinomas

Prognostic stratification of patients surgically resected with invasive pulmonary adenocarcinoma must be improved. Previous studies reported that complex glandular patterns (CGPs), cribriform and fused gland growth patterns, are associated with unfavorable prognosis. The goal of this study is to evaluate the prognostic value of CGPs in patients with resected stage I-IV lung adenocarcinoma. The presence of CGPs as a minor to predominant component was tested for association with overall survival (OS, n = 676) and relapse-free survival (RFS, n = 463) after surgery. CGPs were observed in 284 tumors (42.0%). Cribriform and fused gland were the predominant patterns in 35 and 37 cases, respectively. The presence of cribriform pattern was associated with worse RFS, but not OS. The fused gland pattern alone or grouped into CGPs with the cribriform pattern was not associated with OS and RFS. As a predominant pattern, cribriform was associated with the worse survival compared to the 5 recognized histologic patterns. Patients with fused gland-predominant tumors had 5-year survival that ranged between papillary- and micropapillary-predominant tumors. We conclude that cribriform-predominant, but not fused gland-predominant, is a subtype with poor prognosis similar to the solid and micropapillary subtypes. In contrast, the presence of a minor component of fused gland or CGPs (cribriform + fused gland) is not associated with survival. The cribriform pattern alone offers prognosis stratification improvement, but this effect is attenuated when combined into CGPs to define a subset of acinar-predominant tumors with poor prognosis. This argues against combining cribriform and fused gland into CGPs to summarize high-grade patterns.