Thoracic Oncology
Multiple tumor nodules in lung cancer diagnosis
Low dose CT (LDCT) scan screening for lung cancer is a recommended preventative modality for adults with a significant smoking history (Mayer et al. Ann Int Med. 2014;160(5):330). The screening approach aims to identify adults at significant risk for lung cancer. The goal is to discover lung cancers at low stage with benign mediastinal nodes for optimal treatment and potential for cure. In a minority, but significant number of cases, the LDCT demonstrates multiple lung nodules or masses confounding the attempt to adequately stage the tumor. Two tumors representing a primary cancer and separate malignant spread, namely, intra-pulmonary metastases, in the same lobe, different ipsilateral lobe, or contralateral lobe would be staged, respectively, as T3, T4, or M1a (Detterbeck et al. Chest. 2013;143(5):e191S). Clearly, if the two tumors are separate unique primary cancers, independent of one another, then at best they would be considered as multiple T1 tumors. The treatment modalities of and clinical survival outcomes for these multiple conditions would be markedly different.
The identification of additional tumors may be synchronous (at the same time of the primary discovery) or metachronous (at a later time than the primary discovery). The approach is basically the same. Two tumors with different histologic types, or having separate in-situ squamous cell carcinoma patterns, or disparate immunohistochemical or molecular expressions, or different genomic profiles or driver mutations may be considered as separate distinct primary malignancies (Detterbeck et al. J Thorac Oncol. 2016;11:639; Nicholson et al. J Thorac Oncol. 2017;13:205). Separate foci of ground-glass opacities with small solid central component indicative of minimally invasive adenocarcinoma may be designated as the highest T-stage. These cited and more challenging cases should be presented to a lung cancer tumor board with multiple specialties represented for analysis and judgment. The approach to diagnostic decision-making and clinical management should involve the expertise of all specialties in the lung cancer patient care team.
Arnold M. Schwartz, MD, PhD, FCCP
Steering Committee Member