Ground-glass opacity component in semi-solid lesions: how much is enough?

Abstract

With more at-risk individuals presenting for low-dose CT screening for lung cancer, lesions that may or may not be pathologic are being identified [1, 2]. It is well recognized that pure ground-glass opacities, commonly found in screening studies, often have a low malignant potential and may be either adenocarcinoma in situ or minimally invasive adenocarcinoma though many may also be invasive or have an invasive component [3, 4]. It is the semi-solid lesions where significant questions regarding malignant potential arise. How much of a solid component should prompt definitive therapy, specifically resection, and is lobectomy the appropriate treatment for such lesions or does an anatomic segmentectomy or wedge resection suffice? [5] Kamigaichi et al. [6] have taken an opposite approach asking the question what is the clinical effect on aggressiveness of a small ground-glass component on an otherwise solid lesion. In a retrospective study of 988 consecutive patients with T1 lesions, they looked specifically at the consolidation-to-tumour ratio (CTR), as defined by the solid tumour component as a percentage of maximum tumour diameter as measured by high-resolution CT scanning. A CTR of 1 defines a pure-solid tumour while a nearly pure-solid tumour is defined as 0.75 ≤ CTR < 1. In this study, carried out with patients accrued from 3 institutions, there may be some variability in estimating the size of the ground glass component, especially in retrospect, but the CT scanning technique was consistent between the institutions.