BACKGROUND: Invasive mucinous adenocarcinoma (IMA) is a rare subtype of invasive lung adenocarcinoma. However, the clinical course and prognostic outcomes following IMA resection, particularly postoperative recurrence, remain unclear. METHODS: We pathologically reevaluated 1362 lung adenocarcinoma resections performed at our institution, categorizing cases into the IMA group (72 cases) and non-IMA group (1290 cases). The IMA group was further classified into pneumonia and nodular types based on preoperative computed tomography. RESULTS: Overall, the IMA group had lower carcinoembryonic antigen levels (3 vs 8 ng/mL; P < .01), fewer lymph node metastasis (4% vs 24%; P < .01), and more KRAS mutations (56% vs 7%; P < .01) than the non-IMA group. Although postoperative recurrence rates did not differ between both groups (32% vs 27%; P = 0.35), lung recurrence occurred more frequently in the IMA group (83% vs 17%; P < .01). Propensity score-matched pair analysis showed that the IMA group had fewer lymph node metastasis (3% vs 35%; P < .01), more KRAS mutations (56% vs 9%; P < .01), and higher intrapulmonary recurrence rate (84% vs 31%; P < .01) than the non-IMA group. The 5-year overall survival rates did not differ between both groups (74% vs 81%; P = 0.26). However, among patients with intrapulmonary recurrence, those in the IMA group had significantly worse prognosis than those in the non-IMA group (35% vs 77%; P < .01). CONCLUSIONS: Intrapulmonary recurrence, which induced significantly worse prognosis, was more likely to occur in the IMA than non-IMA group.
BACKGROUND:Invasive mucinous adenocarcinoma (IMA) is a rare subtype of invasive lung adenocarcinoma. However, the clinical course and prognostic outcomes following IMA resection, particularly postoperative recurrence, remain unclear. METHODS: We pathologically reevaluated 1362 lung adenocarcinoma resections performed at our institution, categorizing cases into the IMA group (72 cases) and non-IMA group (1290 cases). The IMA group was further classified into pneumonia and nodular types based on preoperative computed tomography. RESULTS: Overall, the IMA group had lower carcinoembryonic antigen levels (3 vs 8 ng/mL; P < .01), fewer lymph node metastasis (4% vs 24%; P < .01), and more KRAS mutations (56% vs 7%; P < .01) than the non-IMA group. Although postoperative recurrence rates did not differ between both groups (32% vs 27%; P = 0.35), lung recurrence occurred more frequently in the IMA group (83% vs 17%; P < .01). Propensity score-matched pair analysis showed that the IMA group had fewer lymph node metastasis (3% vs 35%; P < .01), more KRAS mutations (56% vs 9%; P < .01), and higher intrapulmonary recurrence rate (84% vs 31%; P < .01) than the non-IMA group. The 5-year overall survival rates did not differ between both groups (74% vs 81%; P = 0.26). However, among patients with intrapulmonary recurrence, those in the IMA group had significantly worse prognosis than those in the non-IMA group (35% vs 77%; P < .01). CONCLUSIONS: Intrapulmonary recurrence, which induced significantly worse prognosis, was more likely to occur in the IMA than non-IMA group.