The Significance of Minimally Invasive Adenocarcinoma in the Classification of Pulmonary Tumors.
Lauren F Xu, Richard Battafarano, Whitney Burrows, Allen P Burke. University of Maryland, Baltimore; Uninversity of Maryland, Baltimore
Background: The classification of lung adenocarcinomas especially those with lepidic spread or bronchioloalveolar carcinoma (BAC) features is controversial. Currently, the determination of T stage (invasive size) in adenocarcinomas with lepidic spread is not well defined. Recently, a new classification system introduced a new category for adenocarcinomas known as minimally invasive adenocarcinoma (MIA) for small solitary adenocarcinomas with predominant lepidic growth and ≤5mm invasion. This distinction is made because patients in this category have 100% or near 100% disease specific survival after complete tumor resection.
Design: We retrospectively reviewed 88 resected adenocarcinomas of the lung and re-classified them as either acinar, solid, mucinous, colloid, papillary, enteric, or micropapillary. Tumors with peripheral lepidic spread (so-called BAC features) were identified, and only the invasive component measured. The tumor stage was compared before and after resizing the tumor using only the invasive component.
Results: There were 29 invasive tumors with lepidic spread (33%), 26 nonmucinous, and 3 mucinous. There were 3 non-invasive nonmucinous BACs. The lepidic extent ranged from 2 mm to 5 cm (mean 2.9 mm). When measuring only the invasive component for staging, 11/26 lepidic non-mucinous tumors were downstaged with 8 to minimally invasive tumors (<5 mm). 3 of 3 mucinous lepidic tumors were also reduced in T stage. Regional lymph nodes were positive in 0/3 non-invasive, 0/8 minimally invasive tumors, 2/29 invasive tumors with lepidic spread (7%), 9/39 of acinar and papillary carcinomas (23%), and 6/17 tumors with a solid growth pattern (35%).
Conclusions: In this series, approximately 1/3 of lung adenocarcinomas have significant lepidic spread. Measuring only invasive component as compared to measuring the entire tumor decreases the T stage in over 1/3 of the cases. Regional lymph node metastases were not present in minimally invasive tumors < 5mm in this series.
Tuesday, March 1, 2011 1:00 PM
Poster Session IV # 274, Tuesday Afternoon