Lung adenocarcinoma with micropapillary and solid patterns: Recurrence rate and trends

BACKGROUND: Lung adenocarcinomas with micropapillary pattern (MP) or solid pattern (SP) have poor prognosis with frequent postoperative recurrence. However, treatment strategies for these histological subtypes have not been established. This study examined the recurrence rates and patterns in patients with these histological subtypes. METHODS: Overall, 238 patients with lung adenocarcinoma who underwent radical resection were included. According to the histological subtypes, the patients were classified into three groups: neither MP nor SP (MP−/SP−), MP (MP+), and SP (SP+). The clinical and pathological characteristics and recurrence‐free survival (RFS) were examined in each group. In addition, univariate and multivariate analyses were performed to investigate the recurrence factors. The site of recurrence, PD‐L1 expression, and driver mutations were examined in patients with postoperative recurrence. RESULTS: The recurrence rates were significantly higher in the MP+ and SP+ groups (p = 0.01). The RFS was significantly shorter in the MP+ and SP+ groups (p < 0.001) than in the MP−/SP− group, especially in pStage 1A (p = 0.001). The relationship between recurrence and pathologic factors was significant for pleural, lymphatic, and vascular invasion, as well as MP in univariate analysis and only for MP in multivariate analysis. Most recurrences were distant metastases in the MP+ and SP+ groups. PD‐L1 was highly expressed in recurrent SP+ cases. CONCLUSIONS: Early‐stage lung adenocarcinoma with MP or SP frequently has postoperative recurrence. Prevention of distant metastases is important in these patients to improve prognosis, and aggressive postoperative chemotherapy may be considered.