Abstract
Simple SummaryPulmonary invasive mucinous adenocarcinoma (IMA) is a recognized variant of lung adenocarcinoma (ADC) that has unique histological patterns. Comprehensively clinical studies and pathological analyses on IMAs have been limited because IMA is rarely diagnosed compared with other subtypes. We compared the clinical characteristics, pathological features, and survival outcomes of 77 IMA patients with 520 non-IMA-type ADC patients. Currently, IMAs lack a simple pathological prognostic grading system to predict survival. We therefore proposed a simple two-tier grading system, which was modified from the low- and high-grade PanIN grading system, to evaluate its prognostic value. We found that IMAs have more distinct clinicopathological characteristics compared to non-IMA-type ADCs. For patients with stage I–IIIA IMA, a new two-tier grading system might be useful in predicting recurrence-free survival. We demonstrated that stage I and II IMAs have better overall survival compared with non-IMA-type ADCs.Pulmonary invasive mucinous adenocarcinoma (IMA) has unique histological patterns. This study aimed to comprehensively evaluate the clinicopathological features, prognosis, and survival outcomes of IMAs. We retrospectively identified 77 patients with pulmonary IMA and reviewed their clinical and pathological features. Another 520 patients with non-IMA-type ADC were retrieved for comparison with patients with IMA. A new two-tier grading system (high-grade and low-grade IMAs) modified from the pancreatic intraepithelial neoplasia classification system was used for survival analyses. Compared to patients with non-IMA-type ADC, patients with IMA tended to have never smoked (p = 0.01) and had early-stage IMA at initial diagnosis (p < 0.001). For stage I–II diseases, the five-year overall survival (OS) rates were 76% in IMAs and 50% in non-IMA-type ADCs, and a longer OS was observed in patients with IMA (p = 0.002). KRAS mutations were the most commonly detected driver mutations, which occurred in 12 of the 28 (43%) patients. High-grade IMAs were associated with a shorter recurrence-free survival (RFS) for stage I–IIIA diseases (p = 0.010) than low-grade IMAs but not for OS. In conclusion, patients with stage I and II IMA had better OS than those with non-IMA-type ADC. A new two-tier grading system might be useful for predicting RFS in stage I–IIIA IMAs.
Highlights
Lung adenocarcinoma (ADC) is the most common primary lung cancer, and its prevalence has increased in recent years
There were no significant differences in age, sex, Eastern Cooperative Oncology Group (ECOG) performance score, and history of other primary malignancies between patients with invasive mucinous adenocarcinoma (IMA) and patients with non-IMA-type ADC
It was not difficult to detect the high-grade, PanIN3-like component because the high-grade area typically comprised more than 10% of the total tumor and sometimes was the predominant component of the tumor. Using this two-tier grading system, we found that high-grade IMA (IMA-G2) was associated with poor recurrence-free survival (RFS) in stage I–II or I–IIIA pulmonary invasive ADCs
Summary
Lung adenocarcinoma (ADC) is the most common primary lung cancer, and its prevalence has increased in recent years. Pulmonary invasive mucinous ADC (IMA), a distinct histological variant of lung ADC, accounts for approximately 5% of lung ADCs [1]. Previous studies have suggested that IMAs might have more distinguished clinical, genetic, and pathological features compared to conventional lung ADCs [3,4,5]. A comparison of clinical characteristics between IMAs and other subgroups of lung ADCs has been reported in previous studies. Patients with IMA tended to have an earlier tumor stage than those with other types of lung ADC [6]. Another study demonstrated that in stage IV cases, patients with IMA frequently had lower lobe tumor mass, initial bilateral lung involvement, and pneumonia-like consolidation on chest tomography [5,7]
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