Invasive Mucinous Adenocarcinomas With Spatially Separate Lung Lesions: Analysis of Clonal Relationship by Comparative Molecular Profiling

Abstract

Introduction: Pulmonary invasive mucinous adenocarcinomas (IMAs) often present with spatially separate lung lesions. Clonal relationship between such lesions, particularly those involving contralateral lobes, is not well established. Here, we used comparative genomic profiling to address this question.

Methods: Patients with genomic analysis performed on two IMAs located in different lung regions were identified. Molecular assays included DNA-based next-generation sequencing (NGS) for 410 to 468 genes (Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets), RNA-based NGS for 62 genes (Memorial Sloan Kettering-Fusion), or non-NGS assays.

Results: Comparative genomic profiling was performed on two separate IMAs in 24 patients, of whom 19 had contralateral lesions. Tumors from all but one patient shared matching driver alterations, including KRAS (n = 19), NRG1 (n = 2), ERBB2 (n = 1) or BRAF (n = 1). In addition, in patients with paired tumors profiled by NGS (n = 12), shared driver alterations were accompanied by up to 4 (average 2.6) other identical mutations, further supporting the clonal relationship between the tumors. Only in a single patient separate IMAs harbored entirely nonoverlapping mutation profiles, supporting clonally unrelated, distinct primary tumors. Notably, in a subset of patients (n = 3), molecular testing confirmed a clonal relationship between the original resected IMAs and subsequent contralateral IMA presenting after an extremely long latency (8.1-11.7 y).

Conclusions: Comparative molecular profiling supports that nearly all separate pulmonary IMA lesions represent intrapulmonary spread arising from a single tumor and documents a subset with a remarkably protracted course of intrapulmonary progression. This study reinforces the unique biology and clinical behavior of IMAs while further highlighting the value of genomic testing for clarifying the clonal relationship between multiple lung carcinomas.

Keywords: Comparative molecular profiling; Invasive mucinous adenocarcinoma; KRAS; Lung; Molecular diagnostics; NSCLC.

Figure 1:. Summary of genomic findings.

The top rows show the patient number and the individual tumor designations as T1 and T2. ^#Initial testing by Sanger sequencing or MALDI-TOF MS resulted in a false-negative result; the mutation was detected only after re-testing with a locked nucleic acid-PCR sequencing. *Additional shared alterations other than the shared pathogenic MAPK alterations as provided in the panel above.

Figure 2:. Radiologic, histologic, and genomic findings for select tumor pairs that were analyzed using next-generation sequencing.

A-D: Tumor pairs classified as clonally related. E: The sole patient in this study with tumor pair classified as clonally unrelated (separate primary IMAs). Histologic sections (20x objective) and the molecular results are provided below. The IMA-specific prevalence is provided for each genetic alteration in parenthesis. Probability of chance co-occurrence is provided for pairs with shared genetic alterations (A-D).

Figure 3:. Radiologic presentation and the timeline of progression of clonally-related IMAs.

Progression timeline for patients with metachronous tumors (A) and synchronous tumors (B), and (C) overall survival based on the presence of pneumonic infiltrates. Each row represents individual patients and the course of their disease. The horizontal axis represents time in years. Shading legend: red death of disease (DD), gray death of other causes (DOC), blue no evidence of disease (NED) and yellow alive with disease (AWD). T1 and T2 refer to index lesions that underwent molecular analysis. Superscript values represent additional lesions identified radiologically.