Differentiation of primary and metastatic tumours in synchronous multifocal colonic and bronchopulmonary adenocarcinoma by targeted next-generation sequencing

Differential diagnosis of pulmonary enteric adenocarcinoma and metastatic colorectal carcinoma with the assistance of next-generation sequencing and immunohistochemistry

PURPOSE

Pulmonary enteric adenocarcinoma (PEAC), defined as tumors with an enteric component exceeding 50% and a histological morphology similar to colorectal cancer (CRC) and metastatic colorectal carcinoma (MCC), is an extremely rare primary lung adenocarcinoma, which was recently recognized by World Health Organization (WHO). Adenocarcinomas with intestinal differentiation have also been described in other anatomic sites, including paranasal sinuses, extrahepatic biliary tree, uterine and cervix, ovary. The morphologic spectrum and immunohistochemical profiles of PEAC overlap with those of colonic adenocarcinomas, the diagnosis of PEAC remains challenging. Currently, colonoscopy has to be performed to confirm the diagnosis, resulting in low compliance due to its invasiveness. Due to the rareness of PEAC, its molecular signature has not been comprehensively examined.

METHODS

In this study, we investigated the molecular signatures associated with PEAC and its histological counterparts, CRC and MCC using capture-based targeted sequencing.

RESULTS

We revealed that 12/13 (92.31%) PEAC patients harbored mutations in well-established driver genes for non-small cell lung cancer and none of them had mutations unique to CRC. Furthermore, 13/15 (86.7%) of MCC harbored mutations that are frequently seen in CRC.

CONCLUSION

Collectively, our study showed that PEAC, exhibiting a similar mutational profile with NSCLC, showed a distinctive signature from CRC and MCC. Furthermore, we derived a classification model, intergrading both IHC markers and genetic signature, to accurately diagnose PEAC.

Next-Generation Sequencing: A Novel Approach to Distinguish Multifocal Primary Lung Adenocarcinomas from Intrapulmonary Metastases

Distinguishing between multiple lung primary tumors and intrapulmonary metastases is imperative for accurate staging. The American Joint Committee on Cancer (AJCC) criteria are routinely used for this purpose but can yield equivocal conclusions. This study evaluated whether next-generation sequencing (NGS) using the 50-gene AmpliSeq Cancer Hotspot Panel version 2 can help facilitate this distinction. NGS was performed on known primary-metastatic pairs (8 patients) and multiple lung adenocarcinomas (11 patients). Primary-metastatic pairs had high mutational concordance. Seven pairs shared mutations, and 1 was concordant for having no mutations. Driver mutations in KRAS (n = 4), EGFR (n = 2), and BRAF (n = 1) were always concordant. Multiple lung tumors from 3 patients were completely concordant and predicted by NGS to be intrapulmonary metastases, whereas 8 had completely discordant mutations and were predicted to be independent primary tumors. The NGS prediction correlated with the AJCC (eighth edition) prediction in all patients for whom the latter was unequivocal (8 of 11). Furthermore, it separated patients by overall survival. Patients with predicted multiple independent primary tumors by NGS had better survival than those with distant metastases (P = 0.016, log-rank test), whereas those with predicted intrapulmonary metastases had no difference (P = 0.527). With further validation, the 50-gene panel has the potential to serve as an adjunct to the AJCC criteria.

Comprehensive Genomic Profiling Aids in Distinguishing Metastatic Recurrence from Second Primary Cancers

BACKGROUND

Metastatic recurrence after treatment for locoregional cancer is a major cause of morbidity and cancer-specific mortality. Distinguishing metastatic recurrence from the development of a second primary cancer has important prognostic and therapeutic value and represents a difficult clinical scenario. Advances beyond histopathological comparison are needed. We sought to interrogate the ability of comprehensive genomic profiling (CGP) to aid in distinguishing between these clinical scenarios.

MATERIALS AND METHODS

We identified three prospective cases of recurrent tumors in patients previously treated for localized cancers in which histologic analyses suggested subsequent development of a distinct second primary. Paired samples from the original primary and recurrent tumor were subjected to hybrid capture next-generation sequencing-based CGP to identify base pair substitutions, insertions, deletions, copy number alterations (CNA), and chromosomal rearrangements. Genomic profiles between paired samples were compared using previously established statistical clonality assessment software to gauge relatedness beyond global CGP similarities.

RESULTS

A high degree of similarity was observed among genomic profiles from morphologically distinct primary and recurrent tumors. Genomic information suggested reclassification as recurrent metastatic disease, and patients received therapy for metastatic disease based on the molecular determination.

CONCLUSIONS

Our cases demonstrate an important adjunct role for CGP technologies in separating metastatic recurrence from development of a second primary cancer. Larger series are needed to confirm our observations, but comparative CGP may be considered in patients for whom distinguishing metastatic recurrence from a second primary would alter the therapeutic approach. The Oncologist 2017;22:152-157Implications for Practice: Distinguishing a metastatic recurrence from a second primary cancer can represent a difficult clinicopathologic problem but has important prognostic and therapeutic implications. Approaches to aid histologic analysis may improve clinician and pathologist confidence in this increasingly common clinical scenario. Our series provides early support for incorporating paired comprehensive genomic profiling in clinical situations in which determination of metastatic recurrence versus a distinct second primary cancer would influence patient management.

USING SOMATIC MUTATION DATA TO TEST TUMORS FOR CLONAL RELATEDNESS

A major challenge for cancer pathologists is to determine whether a new tumor in a patient with cancer is a metastasis or an independent occurrence of the disease. In recent years numerous studies have evaluated pairs of tumor specimens to examine the similarity of the somatic characteristics of the tumors and to test for clonal relatedness. As the landscape of mutation testing has evolved a number of statistical methods for determining clonality have developed, notably for comparing losses of heterozygosity at candidate markers, and for comparing copy number profiles. Increasingly tumors are being evaluated for point mutations in panels of candidate genes using gene sequencing technologies. Comparison of the mutational profiles of pairs of tumors presents unusual methodological challenges: mutations at some loci are much more common than others; knowledge of the marginal mutation probabilities is scanty for most loci at which mutations might occur; the sample space of potential mutational profiles is vast. In this article we examine this problem and propose a test for clonal relatedness of a pair of tumors from a single patient. Using simulations, its properties are shown to be promising. The method is illustrated using several examples from the literature.