Multiple primary lung cancer (MPLC) refers to patients with two or more primary lesions of lung cancer. It can be divided into synchronous MPLC (sMPLC) and metachronous MPLC (mMPLC) based on the timing of occurrence. In recent years, the detection rate of MPLC has gradually increased. However, considerable controversy exists in distinguishing MPLC from intrapulmonary metastasis (IM), especially when the histopathological types are identical. Given the significant differences in treatment strategies and prognosis in clinical practice currently, accurate diagnosis of MPLC is crucial for personalized precision therapy. Molecular genetics and sequencing technologies offer effective strategies for assessing the clonal origin of tumors. There have been reports of coexisting mutations in the epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK) fusion genes in non-small cell lung cancer, but case of EGFR mutation following an ALK mutation has not been mentioned. This article accurately diagnoses and retrospectively analyzes the clinical data of a case of ALK mutant adenocarcinoma in a male patient who developed an EGFR mutation with multiple metastases four years after surgery, and reviews the relevant literature. This paper aims to deepen the understanding of mMPLC and provide clinical references for the diagnosis and treatment of such patients.
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【中文题目：EGFR和ALK基因异时性突变非小细胞肺癌
1例报告并文献复习】 【中文摘要：多原发肺癌（multiple primary lung cancer, MPLC）指患者有两个或两个以上原发病灶的肺癌，根据发生时间的不同分为同时性多原发肺癌（synchronous MPLC, sMPLC）和异时性多原发肺癌（metachronous MPLC, mMPLC）。近年来，MPLC的检出率逐渐升高，但由于肿瘤的异质性，在鉴别MPLC和肺内转移（intrapulmonary metastasis, IM）上存在许多争议，特别是病理组织学类型相同时。考虑到目前二者在临床治疗策略及预后上的显著差异，对于MPLC和IM的精确诊断是个体化精准治疗的关键。分子遗传学及测序技术为检测肿瘤的克隆性起源提供了有效的策略，其中非小细胞肺癌表皮生长因子受体（epidermal growth factor receptor, EGFR）突变与间变性淋巴瘤激酶（anaplastic lymphoma kinase, ALK）融合突变共存的病例陆续有报道，但ALK基因突变后再发EGFR突变的案例未见提及。本文通过分子遗传学技术准确诊断并回顾性分析了1例ALK突变型男性肺腺癌患者术后4年再发EGFR突变合并多发转移的临床资料，并复习相关文献，以期加深对mMPLC的认识，为该类病例的诊疗提供临床借鉴。
】 【中文关键词：异时性多原发肺癌；肺内转移；EGFR；ALK】.

The distinction between separate primary lung carcinomas (SPLCs) and intrapulmonary metastases (IPMs) is crucial to accurate cancer staging. Histopathology-based classification cannot always determine the relatedness of multiple tumors taken from the lung. Recently, next-generation sequencing (NGS) has been used for biomarker determination, but it also has the potential to inform clonality determination among multiple tumors. Here we present a patient with three lung tumors, each diagnosed as adenocarcinoma by histopathology with a differential diagnosis of SPLC versus IPM. We pursued molecular profiling by NGS, which revealed three unique mutational patterns ruling out the possibility of clonal relatedness among the cancers. Our case supports the utility of NGS in supplementing histopathological methods to distinguish between SPLCs and IPMs and to guide treatment decisions.

Non-small cell lung carcinomas (NSCLCs) commonly present as 2 or more separate tumors. Biologically, this encompasses 2 distinct processes: separate primary lung carcinomas (SPLCs), representing independently arising tumors, and intrapulmonary metastases (IPMs), representing intrapulmonary spread of a single tumor. The advent of computed tomography imaging has substantially increased the detection of multifocal NSCLCs. The strategies and approaches for distinguishing between SPLCs and IPMs have evolved significantly over the years. Recently, genomic sequencing of somatic mutations has been widely adopted to identify targetable alterations in NSCLC. These molecular techniques have enabled pathologists to reliably discern clonal relationships among multiple NSCLCs in clinical practice. However, a standardized approach to evaluating and staging multiple NSCLCs using molecular methods is still lacking. Here, we reviewed the historical context and provided an update on the growing applications of genomic testing as a clinically relevant benchmark for determining clonal relationships in multiple NSCLCs, a practice we have designated \"comparative molecular profiling.\" We examined the strengths and limitations of the morphology-based distinction of SPLCs vs IPMs and highlighted pivotal clinical and pathologic insights that have emerged from studying multiple NSCLCs using genomic approaches as a gold standard. Lastly, we suggest a practical approach for evaluating multiple NSCLCs in the clinical setting, considering the varying availability of molecular techniques.

BACKGROUND: It is clinically challenging to infer the phylogenetic relationship between different tumor lesions of patients with multiple synchronous lung cancers (MSLC), whether these lesions are the result of independently evolved tumor or intrapulmonary metastases.
METHODS: We used the Illumina X10 platform to sequence 128 stage I lung cancer samples collected from 64 patients with MSLC. All samples were analyzed for mutation spectra and phylogenetic inference.
RESULTS: We detected genetic aberrations within genes previously reported to be recurrently altered in lung adenocarcinoma including, EGFR, ERBB2, TP53, BRAF, and KRAS. Other putative driver mutations identified were enriched in RTK-RAS signaling, TP53 signaling, and cell cycle. Also, we found some interesting cases, two cases that carried EGFR L858R and T790M co-mutation in one tumor and another tumor with only EGFR 19del, and 1 case with two KRAS hotspots in the same tumor. Due to the short follow-up time and early stage, further investigation is needed to determine whether this unique mutation profile will affect their progression-free survival (PFS) and overall survival (OS). Regarding genetic evolution analysis among 64 tumor samples, 50 of them display distinct mutational profiles, suggesting these are independently evolved tumors, which is consistent with histopathological assessment. On the other hand, six patients were identified to be intrapulmonary metastasis as the mutations harbored in different lesions are clonally related.
CONCLUSIONS: In summary, unlike intrapulmonary metastases, patients with MSLC harbor distinct genomic profiles in different tumor lesions, and we could distinguish MSLC from intrapulmonary metastases via clonality estimation.

UNASSIGNED: Treatments for multiple ground-glass opacities (GGOs) for which the detection rate is increasing are still controversial. Next-generation sequencing (NGS) may provide additional key evidence for differential diagnosis or optimal therapeutic schedules.
UNASSIGNED: We first reported a rare case in which more than 100 bilateral pulmonary GGOs (91.7% of the GGOs were pure GGOs) were diagnosed as both multiple primary lung cancer and intrapulmonary metastasis. We performed NGS with an 808-gene panel to assess both somatic and germline alterations in tissues and plasma. The patient (male) underwent three successive surgeries and received osimertinib adjuvant therapy due to signs of metastasis and multiple EGFR-mutated tumors. The patient had multiple pure GGOs, and eight tumors of four pathological subtypes were evaluated for the clonal relationship. Metastasis, including pure GGOs and atypical adenomatous hyperplasia, was found between two pairs of tumors. Circulating tumor DNA (ctDNA) monitoring of disease status may impact clinical decision-making.
UNASSIGNED: Surgery combined with targeted therapies remains a reasonable alternative strategy for treating patients with multifocal GGOs, and NGS is valuable for facilitating diagnostic workup and adjuvant therapy with targeted drugs through tissue and disease monitoring via ctDNA.

UNASSIGNED: Multiple lung cancers may present as multiple primary lung cancers (MPLC) or intrapulmonary metastasis (IPM) with variations in clinical stage, treatment, and prognosis. However, the existing differentiation criteria based on histology do not fully meet the clinical needs. Next-generation sequencing (NGS) may play an important role in assisting the identification of different pathologies. Here, we extended the relevant data by combining histology and NGS to develop detailed identification criteria for MPLC and IPM.
UNASSIGNED: Patients with lung cancer (each patient had ≥2 tumors) were enrolled in the training (n = 22) and validation (n = 13) cohorts. Genomic profiles obtained from 450-gene-targeted NGS were analyzed, and the new criteria were developed based on our findings and pre-existing Martini & Melamed criteria and molecular benchmarks.
UNASSIGNED: The analysis of the training cohort indicated that patients identified with MPLC had no (or <2) trunk or shared mutations. However, 98.02% of mutations were branch mutations, and 69.23% of MPLC had no common mutations. In contrast, a higher percentage of trunk (33.08%) or shared (9.02%) mutations were identified in IPM, suggesting significant differences among mutated components. Subsequently, eight MPLC and five IPM cases were identified in the validation cohort, aligning with the independent imaging and pathologic distinction. Overall, the percentage of trunk and shared mutations was higher in patients with IPM than in patients with MPLC. Based on these results and the establishment of new determination criteria for MPLC and IPM, we emphasize that the type and number of shared variants based on histologic consistency assist in identification.
UNASSIGNED: Determining genetic alterations may be an effective method for differentiating MPLC and IPM, and NGS can be used as a valuable assisting tool.

OBJECTIVE: Metachronous lung cancer arising after resection of non-small-cell lung cancer is either a second primary lung cancer (SPLC) or intrapulmonary metastasis (IPM) of the initial lung cancer; however, differential diagnosis is difficult. We evaluated the surgical outcomes of metachronous lung cancer in a combined population of patients with SPLC and IPM.
METHODS: A retrospective study of 3534 consecutive patients with resected non-small-cell lung cancer between 1992 and 2016 was conducted at 4 institutions.
RESULTS: A total of 105 patients (66 males; median age, 70 years) who underwent a second pulmonary resection for metachronous lung cancer were included. Most patients (81%) underwent sublobar resection, and there was no 30-day mortality. All metachronous lung cancers were cN0, 5 were pN1-2. The postoperative comprehensive histologic assessment revealed SPLC (n = 77) and IPM (n = 28). The 5-year overall survival rate after the second resection was 70.6% (median follow-up: 69.7 months). A multivariable analysis showed that age >70 years at the second resection (P = 0.013), male sex (P = 0.003), lymph node involvement in metachronous cancer (P < 0.001), pathological invasive size of metachronous cancer >15 mm (P < 0.001) and overlapping squamous cell carcinoma histology of the initial and metachronous cancers (P = 0.003) were significant prognostic factors for poor survival after the second resection, whereas histological IPM was not (P = 0.065).
CONCLUSIONS: Surgery for cN0 metachronous lung cancer is safe and shows good outcomes. There were no statistically significant differences in the SPLC and IPM results. Caution should be exercised when operating on patients with overlapping squamous cell carcinoma.

UNASSIGNED: Distinguishing multiple primary lung cancer (MPLC) from intrapulmonary metastasis (IPM) is critical for their disparate treatment strategy and prognosis. This study aimed to establish a non-invasive model to make the differentiation pre-operatively.
UNASSIGNED: We retrospectively studied 168 patients with multiple lung cancers (307 pairs of lesions) including 118 cases for modeling and internal validation, and 50 cases for independent external validation. Radiomic features on computed tomography (CT) were extracted to calculate the absolute deviation of paired lesions. Features were then selected by correlation coefficients and random forest classifier 5-fold cross-validation, based on which the lesion pair relation estimation (PRE) model was developed. A major voting strategy was used to decide diagnosis for cases with multiple pairs of lesions. Cases from another institute were included as the external validation set for the PRE model to compete with two experienced clinicians.
UNASSIGNED: Seven radiomic features were selected for the PRE model construction. With major voting strategy, the mean area under receiver operating characteristic curve (AUC), accuracy, sensitivity, and specificity of the training versus internal validation versus external validation cohort to distinguish MPLC were 0.983 versus 0.844 versus 0.793, 0.942 versus 0.846 versus 0.760, 0.905 versus 0.728 versus 0.727, and 0.962 versus 0.910 versus 0.769, respectively. AUCs of the two clinicians were 0.619 and 0.580.
UNASSIGNED: The CT radiomic feature-based lesion PRE model is potentially an accurate diagnostic tool for the differentiation of MPLC and IPM, which could help with clinical decision making.

UNASSIGNED: Up to 15% of lung cancer patients have multiple suspicious nodules. While some of these nodules may represent metastatic lung cancer, others represent synchronous multiple primary lung cancer (SMPLC). The incidence of SMPLC ranges from 0.8% to 8.4% and appears to be increasing. Inconsistent identification of SMPLC can be detrimental for patients who are misdiagnosed as having intrapulmonary metastasis and not offered stage-based treatment. We sought to identify the contemporary incidence of SMPLC at a tertiary institution.
UNASSIGNED: From January 2018 to September 2019, patients who underwent lung cancer resection were retrospectively reviewed. Patients with SMPLC were identified using the modified Martini-Melamed criteria.
UNASSIGNED: During the 21-month period, 227 patients underwent lung cancer resection. There were 47 patients (20.7%) who had 119 pathologically confirmed SMPLC. Most patients had ipsilateral tumors (n = 24, 51.1%) with at least 1 adenocarcinoma (n = 40, 85.1%). Considering histologic subtyping, 38 (80.9%) had histologically distinct tumors. Overall and cancer-specific survival at 4 years was 86% and 90%, respectively. Only patients with 3 or more SMPLC had poor 4-year overall (P = 0.002) and cancer-specific survival (P = 0.043) compared with those with 2 SMPLC. Patient demographics, histology, tumor location, and highest pathologic staging did not affect survival outcomes.
UNASSIGNED: Using a strict inclusion criterion, the incidence of SMPLC is higher than previously reported. SMPLC patients have favorable survival outcomes, suggesting that they behave like primary lung cancer, not intrapulmonary metastasis. Awareness of SMPLC by thoracic surgeons is critical in optimizing outcomes in this patient population.

In the era of histopathology-based diagnosis, the discrimination between multiple lung cancers (MLCs) poses significant uncertainties and has thus become a clinical dilemma. However, recent significant advances and increased application of molecular technologies in clonal relatedness assessment have led to more precision in distinguishing between multiple primary lung cancers (MPLCs) and intrapulmonary metastasis (IPMs). This review summarizes recent advances in the molecular identification of MLCs and compares various methods based on somatic mutations, chromosome alterations, microRNAs, and tumor microenvironment markers. The paper also discusses current challenges at the forefront of genomics-based discrimination, including the selection of detection technology, application of next-generation sequencing, and intratumoral heterogeneity (ITH). In summary, this paper highlights an entrance into the primary stage of molecule-based diagnostics.