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P1.02 - Biology/Pathology (ID 614)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: Biology/Pathology
- Presentations: 1
- Coordinates: 10/16/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
P1.02-032 - Clinicopathological Profile of Invasive Mucinous Adenocarcinoma Based on Evaluation of Invasive Components (ID 9335)
09:30 - 16:00 | Author(s): A. Kikuyama
In the new 2015 WHO classification, invasive mucinous adenocarcinoma (IMA), formerly referred to as mucinous BAC, is categorized as variant of invasive adenocarcinoma. IMA has goblet or columnar cell feature with abundant intracytoplasmic mucin and may show the same heterogeneous mixture of histologic subtypes (lepidic, acinar, papillary, and micropapillary) as non-mucinous tumors. In the 8th edition of TNM classification, invasive tumor size is used for T factor, but few comprehensive studies about invasive components of IMA are reported.
We evaluated 460 patients with lung adenocarcinoma surgically resected at our facility from Jan 1, 2000 to Jan 31, 2017. In cases identified as IMA, invasive components (the predominant histologic subtypes, the size of invasive area and the presence of spread through air spaces (STAS)) were noted. We classified all cases with the 8[th] TNM system and investigated the clinical course retrospectively.
24 cases (5.2%) were diagnosed as IMA. Of 24 IMAs, 21 cases (91.3%) expressed CK20 with lack of TTF-1. KRAS mutation was found in 2 of the examined 3 cases. 23 cases (96.3%) were found histologic subtype other than lepidic pattern. All cases of IMA were classified into 16 cases of lepidic predominant IMA and 8 cases of non-lepidic predominant IMA (3 cases of acinar predominant, 5 cases of papillary predominant) depending on the predominant histologic subtype. The proportions of lepidic predominant and non-lepidic predominant IMA in each stages were as follows; IA: 68.8% vs 12.5%, ⅠB: 12.5% vs 37.5%, II: 6.3% vs 25.0%, IIIA: 12.5% vs 25.0%. Lymph node metastasis was observed in only one case of non-lepidic predominant IMA. The recurrence was observed 37.5% (6 of 16, included 3 relapsed cases of StageⅠ) and 37.5% (3 of 8) respectively in the period. STAS was found with a high probability in both category (71.4% vs 100%) and a total of 7 cases were pulmonary recurrence. 5-year DFS did not differ significantly (48.5% vs 51.4%, log rank test p=0.76). 5-year OS was a high tendency for lepidic predominant IMA, but no significant difference was observed (73.9% vs 43.8%, log rank test p=0.14).
Lepidic predominant IMA seemed to be more frequent in early-stage cancer than non-lepidic predominant IMA, but the frequency of relapse in the clinical course was similar in both groups. These results suggest that IMA have a prognostic factor other than patterns of the histologic subtypes and invasive size.
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