For univariate analysis, all cumulative survival was estimated using the Kaplan-Meier method, and differences in variables were calculated using the log-rank test. of SMPC was significantly associated with tumor size, advanced-stage disease, lymph node metastasis, pleural invasion, lymphatic invasion, and vascular invasion. Patients with SMPC(+) tumors had significantly poorer outcomes than those with SMPC-negative tumors. Multivariate analysis revealed that ARP 100 SMPC was a significant independent prognostic factor of lung adenocarcinoma, especially for disease-free survival of pathological stage I individuals ( em p /em = 0.035). SMPC showed significantly higher manifestation of E-cadherin and lower manifestation of CD44 than the related manifestation levels demonstrated by AMPC and showed lower surfactant apoprotein A and phospho-c-Met manifestation level than related manifestation levels demonstrated by tumor cell parts without a micropapillary component. Fourteen instances with SMPC(+) tumors (74%) showed em EGFR /em mutations, and none of them showed em ARP 100 KRAS /em mutations. Conclusions SMPC(+) tumors are rare, but they may be associated with a poor prognosis and have different phenotypic and genotypic characteristics from those of AMPC(+) tumors. Virtual Slides The virtual slide(s) for this article can be found here: Eltd1 http://www.diagnosticpathology.diagnomx.eu/vs/9433341526290040. strong class=”kwd-title” Keywords: lung adenocarcinoma, micropapillary component, stromal micropapillary component, aerogenous micropapillary component, prognostic element Background A new lung adenocarcinoma classification system has been proposed from the International Association for the Study of Lung Malignancy, American Thoracic Society, and Western Respiratory Society (IASLC/ATS/ERS) [1]. With this classification, the micropapillary component (MPC) was recommended as a new subtype of lung adenocarcinoma in addition to the lepidic, acinar, papillary, and solid subtypes defined in the 2004 World Health Corporation (WHO) classification [2]. MPC was defined as tumor cells growing in papillary tufts lacking fibrovascular cores and may float within alveolar spaces. MPC-predominant lung adenocarcinoma shows a high incidence of nodal metastasis and a poor prognosis [3-8]. MPC-predominant carcinomas developing in various other organs, such as the breast and urinary bladder, known as invasive micropapillary carcinoma, also have a poor prognosis. However, localization of MPC in the lungs is definitely significantly different from that in the additional organs; MPC in lung adenocarcinoma is definitely distinguished by floating tumor cells within alveolar spaces (aerogenous micropapillary component, AMPC), while MPC in additional organs has been observed primarily in the stroma as invasive components (stromal invasive micropapillary component, SMPC) [3,4]. Few studies have examined lung adenocarcinoma with SMPC [9,10]. Recently, we reported 2 instances of SMPC-predominant lung adenocarcinoma [9]. The proportion of SMPC in both tumors was greater than 50% in area. We observed that SMPC experienced a strong association with vascular invasion, similar to the instances of SMPC-predominant carcinoma in additional organs. However, a large-scale investigation on pulmonary SMPC has not been conducted. The seeks of this study included: (1) clarifying the incidence of SMPC in lung adenocarcinoma; (2) elucidating the clinicopathological characteristics of the tumor; and (3) determining the prognoses of the SMPC-positive (SMPC(+)) tumors and comparing them with those of SMPC-negative (SMPC(-)) tumors. We examined 559 resected lung adenocarcinomas for this study with carrying out immunohistochemical and genetic analysis. Methods Individuals We analyzed 565 consecutive instances of main lung adenocarcinoma treated by medical resection in the Kanagawa Malignancy Center between February 2007 and December 2010. Formalin fixation of the resected lung cells was performed within 48 hours ARP 100 to reduce the loss of immunohistochemical antigen manifestation and degeneration of DNA. Six individuals who experienced received preoperative chemotherapy were excluded. A total of 559 instances were enrolled in the study. The median follow-up time was 634.5 days (range, 28-1512 days). All individuals provided educated consent, and the studies were performed according to the.