Assessment of invasion in lung adenocarcinoma classification, including adenocarcinoma in situ and minimally invasive adenocarcinoma

Abstract

Classification of adenocarcinoma has undergone recent evaluation to better align histological classification with clinical outcomes. One terminology, in particular, that of bronchioloalveolar carcinoma (BAC), has been debated for many decades. Although initial discussion surrounded the cell-of-origin of this tumor, more recent confusion has been generated from the use of this term both as a pattern of growth within an otherwise invasive adenocarcinoma and as a term for a pre-invasive tumor synonymous with adenocarcinoma in situ. As a result, adenocarcinomas with quite different radiology, gross morphology and metastatic potential have been associated with the BAC term. Focusing on invasion and using an illustrative case, we will explore the current recommendations that incorporate assessment of invasion to clarify the confusion caused by the different uses of the historical term 'BAC'.

RhoB Determines Tumor Aggressiveness in a Murine EGFRL858R-Induced Adenocarcinoma Model and Is a Potential Prognostic Biomarker for Lepidic Lung Cancer

“…This subtype of carcinoma is associated with good survival when it is diagnosed at an early stage, but it can rapidly become invasive, spreading along the bronchial tree, invading through the basal membrane, and eventually leading to a very aggressive phenotype with a poor outcome (38)(39)(40)(41). The crucial event in the progression of this type of cancer is the switch from a "horizontal" spread toward "vertical" invasion of the basal membrane.…”

Root Cause Analysis of Problems in the Frozen Section Diagnosis of In Situ, Minimally Invasive, and Invasive Adenocarcinoma of the Lung

“…In accordance with the new proposed classification, our surgeons now request that a more-precise diagnosis (no invasion versus 5 mm of invasion versus .5 mm of invasion) be made at frozen section. Borczuk 16 recently addressed the assessment of invasion in in situ and minimally invasive adenocarcinoma. Difficulties distinguishing malignant cells from atypical reactive cells based on cytomorphology have long been recognized in the cytology literature and remain as diagnostic problems.…”

In Compressed Lung Tissue Microscopic Sections of Adenocarcinoma In Situ May Mimic Papillary Adenocarcinoma

“…9 Elastin fibers are not present in papillary tumors of other organs, nor are they present in metastases of papillary adenocarcinoma of the lung. In papillary tumors of the lung with very thin fibrovascular cores containing elastin fibers, it is highly likely that these cores are part of the preexisting alveolar wall.…”