High prevalence of ground-glass opacity in synchronous multiple primary lung cancer

Objectives: The detection rate of synchronous multiple primary lung cancer (SMPLC) has risen significantly over the past decades. We herein investigated the clinicopathological, radiological and molecular features of patients with SMPLC. Methods: We retrospectively reviewed and analyzed 97 consecutive patients who were diagnosed with SMPLC at West China Hospital of Sichuan University between 2014 and 2017. The 97 patients were classified into three groups according to the radiological feature of the tumors: 24 patients (24.7%) in Group A (all tumors being solid lesions), 36 (37.1%) in Group B [solid and ground-glass opacity (GGO) tumors coexisting] and 37 (38.2%) in Group C (all tumors being GGO lesions). Results: Of the 97 patients, 73 (75.3%) harbored at least one GGO tumor and 60.3% (129/214) of their surgically resected tumors were GGO tumors. Subgroup analyses found more females (P=0.046), non-smokers (P=0.013) and patients with three tumors (P=0.005) in Group C than in Group A. Additionally, both the largest tumor dimension and the sum of tumor dimension in Group C were smaller than those in Group A (P<0.001 for both). Concordance between histological subtyping and clinical diagnostic criteria was observed in 93.0% (53/57) of patients, and that between genetic analysis and clinical diagnostic criteria was identified in 46.2% (6/13) of patients. Conclusions: GGO tumor was quite common in SMPLC and the clinical characteristics of GGO SMPLC were different from solid SMPLC. Histological subtyping, instead of genotyping, could be advocated as an additional reference to differentiate SMPLC from intrapulmonary metastases.