OBJECTIVETo evaluate the prognostic significance of micropapillary pattern (MPP) in adenocarcinoma of lung.

METHODSNinety-one consecutively excised cases of pulmonary adenocarcinoma, including follow-up data, were retrospectively studied. These tumors were divided into 2 major groups: those with MPP and those without MPP. The former was further subdivided according to extent of the micropapillary component, as follows: MPP + (constituting 1% to 10% of the tumor), MPP ++ (constituting 11% to 30% of the tumor) and MPP +++ (constituting more than 30% of the tumor).

RESULTSThe overall 5-year survival rate was 64.8%. The 5-year survival rates were 88.9% for stage I tumors, 46.2% for stage II tumors, and 23.8% for stage III tumor respectively (P = 0.000). The extent of micropapillary component showed no correlation with tumor stage, size and 5-year survival rate (P = 0.065, 0.358 and 0.206, respectively). On the other hand, the 5-year survival rate was 41.5% for patients in the MPP-positive group (number = 41) and 84.0% for patients in the MPP-negative group (number = 50). The percentage of nodal metastasis in MPP-positive group was also higher than that in MPP-negative group (P = 0.000). In pulmonary adenocarcinoma, this characteristic histology correlated with tumor stage and size, but not with patient's gender and smoking history. Within the same stage, the 5-year survival rates of MPP-positive and MPP-negative groups were as follows: for stage I, 78.6% versus 92.6% (P = 0.1548), for stage II, 30.0% versus 100% (P = 0.0598), and for stage III, 17.7% versus 28.6% (P = 0.4045).

CONCLUSIONSMPP in primary pulmonary adenocarcinoma, even when only constituting a minor component, predicts an aggressive clinical behavior and is associated with poor prognosis. Although it may not be an independent prognostic factor, presence of this histologic pattern should alert clinicians for more active treatment and closer follow up.