Morphologic, Immunohistochemical, and Genetic Differences Between High-grade and Low-grade Fetal Adenocarcinomas of the Lung

Malignant Salivary Gland Neoplasm of the Tongue Base with EWSR1::BEND2 Fusion: An Unusual Case with Literature Review

PURPOSE

Salivary gland malignancies may have overlapping architectural patterns, tumor morphology, and immunohistochemical phenotypes, presenting challenges in precise classification. Molecular phenotyping has become quite useful for providing an additional diagnostic modality, and potential drug targets. Here we reported a young female patient with salivary gland tumor of the tongue base harboring genetic alterations by next generation sequencing (NGS).

METHODS

The morphological, immunohistochemical and molecular features of this case were described, and related literature was reviewed.

RESULTS

The tumor showed an epithelial myoepithelial architecture arranged in cords and tubules interwoven with a chondromyxoid stroma, along with perineural invasion and adjacent striated muscle infiltration. Myoepithelial cells were positive for CK5/6, partially positive for P63 and CK7, and sporadically positive for S100. Immunoprofiling revealed a low density of infiltrating lymphocytes and macrophages and the absence of programmed death ligand 1 (PD-L1). Notably, RNA-based NGS showed EWSR1::BEND2 gene fusion in this tumor, and EWSR1 break-apart was confirmed by fluorescence in situ hybridization. This led to a final diagnosis of a minor salivary gland malignancy with EWSR1::BEND2 fusion. Only two other cases of salivary gland tumors with EWSR1::BEND2 fusion had been previously reported, which were also detected via RNA-based NGS.

CONCLUSION

This study emphasized that EWSR1::BEND2 fusion may drive the carcinogenesis in salivary glands neoplasia. In clinic RNA-based NGS could be essential for precise genotyping of EWSR1 fusion in this rare disease.

Prominent response to savolitinib monotherapy in high-grade fetal adenocarcinoma with MET amplification and concurrent brain metastasis: a case report

Background

Mesenchymal-epithelial transition (MET) represents a potential therapeutic target in various cancers, with amplification of the MET gene identified in a subset of patients with pulmonary adenocarcinomas. However, MET gene amplification is rarely observed in high-grade fetal adenocarcinoma (H-FLAC).

Case Description

Here we present a novel case of a patient diagnosed with stage IV H-FLAC harboring MET amplifications and treated with savolitinib. The 69-year-old male patient, who presented with a primary complaint of cough and white sputum, had a history of hypertension for over 10 years and a 45-year smoking history. The patient received savolitinib monotherapy treatment due to brain metastases. Despite the omission of radiotherapy for asymptomatic brain metastases, a notable response to savolitinib therapy was observed, with a partial response (PR) achieved after 4 weeks and a reduction in the brain tumor. At the time of the submission of this report, the patient received over 24 weeks of savolitinib treatment, and was maintained PR. The patient was still undergoing treatment. This highlights the potential clinical benefits of targeted therapy against MET amplification in H-FLAC.

Conclusions

H-FLAC harboring MET amplification and brain metastasis is rare. Treatment with savolitinib monotherapy resulted in a PR, providing preliminary insights to the efficacy of savolitinib for H-FLAC with MET amplification.

Molecular landscape and multi-omic measurements of heterogeneity in fetal adenocarcinoma of the lung

Fetal adenocarcinoma of the lung (FLAC) is a rare form of lung adenocarcinoma and was divided into high-grade (H-FLAC) and low-grade (L-FLAC) subtypes. Despite the existence of some small case series studies, a comprehensive multi-omics study of FLAC has yet to be undertaken. In this study, we depicted the multi-omics landscapes of this rare lung cancer type by performing multi-regional sampling on 20 FLAC cases. A comparison of multi-omics profiles revealed significant differences between H-FLAC and L-FLAC in a multi-omic landscape. Two subtypes also showed distinct relationships between multi-layer intratumor heterogeneity (ITH). We discovered that a lower genetic ITH was significantly associated with worse recurrence-free survival and overall survival in FLAC patients, whereas higher methylation ITH in H-FLAC patients suggested a short survival. Our findings highlight the complex interplay between genetic and transcriptional heterogeneity in FLAC and suggest that different types of ITH may have distinct implications for patient prognosis.

Clinical and Pathological Characteristics and Prognosis of Lung Adenocarcinoma With High-Grade Fetal Features: A Retrospective Analysis

Fetal adenocarcinoma of the lung is a rare tumor. The clinical and pathological characteristics, treatment, and prognosis of patients with lung adenocarcinoma with fetal lung-like morphology were retrospectively investigated. The tumors of 9 patients with lung adenocarcinoma contained fetal lung-like morphology. One patient had pure-type high-grade fetal adenocarcinoma. Two patients had more than 50% high-grade fetal adenocarcinoma. Six specimens accounted for < 50% of the high-grade fetal features. It occurred in 7 men and 2 women. The median age at diagnosis was 62.0 years. Thyroid transcription factor-1 was frequently expressed in 8 specimens. All 9 specimens showed high rates of immunopositivity for β-catenin and E-cadherin. Three specimens showed nuclear β-catenin staining. Some patients showed immune expression of CDX2, α-fetoprotein (AFP), SALL4, and Glypican-3. Three of these specimens were diffusely strongly positive for p53, including 1 mixed-type high-grade fetal adenocarcinoma and 2 lung adenocarcinomas with high-grade fetal features. However, the other 6 patients had wild-type p53, including 1 pure-type high-grade fetal adenocarcinoma. PD-L1 was not expressed in all patients. Epidermal growth factor receptor mutations were detected in 1 patient. All patients were diagnosed using surgical samples. During the follow-up period of 36 months (range: 1-92 months), 3 patients received chemotherapy. One patient underwent radiotherapy. Two patients experienced recurrences. No patient died. PD-L1 expression status suggests a poor response to immune checkpoint therapy. The prognosis of the patient was relatively good.

Fetal Type Morphologies Suggest the Presence of DICER1 Hotspot Mutations in Non-small Cell Lung Cancer

Germline and somatic pathogenic variants (PVs) in DICER1 , encoding a miRNA biogenesis protein, are associated with a wide variety of highly specific pathologic entities. The lung tumors pleuropulmonary blastoma, pulmonary blastoma (PB), and well-differentiated fetal lung adenocarcinoma (WDFLAC) are all known to harbor DICER1 biallelic variants (loss of function and/or somatic hotspot missense mutations), and all share pathologic features reminiscent of the immature lung. However, the role of DICER1 PVs in non-small cell lung cancer (NSCLC) is relatively unknown. Here, we aimed to establish the spectrum of lung pathologies associated with DICER1 hotspot PVs and to compare the mutational landscape of DICER1 -mutated NSCLC with and without hotspots. We queried DNA sequencing data from 12,146 NSCLCs featuring somatic DICER1 variants. 235 (1.9%) cases harboring ≥ 1 DICER1 PV were found and 9/235 (3.8%) were DICER1 hotspot-positive cases. Histologic review of DICER1 hotspot-positive cases showed that all but one tumor were classified as within the histologic spectrum of PB/WDFLAC, whereas all the DICER1 non-hotspot double variants were classified as lung adenocarcinomas, not otherwise specified. Comparison between the mutational landscape of DICER1 hotspot-positive and hotspot-negative cases revealed a higher frequency of CTNNB1 mutations in the hotspot-positive cases (5/9 vs. 2/225; P <0.00001). We conclude that DICER1 somatic hotspots are not implicated in the most common forms of NSCLC but rather select for morphologic features of lung tumor types such as PB and WDFLAC. As a corollary, cases showing this tumor morphology should undergo testing for DICER1 variants, and if positive, genetic counseling should be considered.

High-grade fetal adenocarcinoma of the lung misdiagnosed as male breast carcinoma: a case report and literature review

Background and aim

High-grade fetal adenocarcinoma of the lung (HG-FLAC) is a specific subtype of lung adenocarcinoma with a poor prognosis. A lack of understanding exists because of the rarity of this disease. This study aimed to present a case of HG-FLAC with multiple metastases misdiagnosed as male breast carcinoma at the initial diagnosis.

Case presentation

The patient visited our hospital due to a month-long cough. The chest computed tomography (CT) scan revealed a mass in the left lung and chest wall, accompanied by enlargement of mediastinal lymph nodes. The magnetic resonance imaging indicated potential metastatic lesions in the brain and adrenal glands. The patient underwent a biopsy of the lesion in the right chest wall. The pathological and immunohistochemical findings indicated a high possibility of male breast cancer. However, the clinical features did not support this diagnosis. Therefore, a CT-guided percutaneous lung biopsy was performed, and the pathological examination finally indicated HG-FLAC.

Conclusions

We presented a complex yet interesting case in which HG-FLAC was misdiagnosed as male breast cancer. Our interesting case may stimulate discussions about the methods to manage patients with HG-FLAC.

KMT2C expression and DNA homologous recombination repair factors in lung cancers with a high-grade fetal adenocarcinoma component

Background

High-grade fetal adenocarcinoma of the lung (H-FLAC) is a rare variant of pulmonary adenocarcinoma. Our previous study showed a high frequency of KMT2C mutations in lung cancers with an H-FLAC component, showing that KMT2C dysfunction may be associated with the biological features of H-FLACs.

Methods

In this study, we performed RNA sequencing and immunohistochemical analysis to identify the differentially expressed genes and corresponding pathways associated with H-FLACs, compared with common adenocarcinomas.

Results

Ingenuity pathway analysis based on RNA sequencing data revealed that DNA homologous recombination repair (HRR) pathways were significantly inactivated in H-FLAC. Expression of KMT2C, ATM, ATR, and BRCA2 was significantly lower in H-FLACs than in common adenocarcinomas, and BRCA1 expression showed a decreasing trend. Pearson correlation analyses for all cases revealed that KMT2C expression showed a strong positive correlation (R>0.7) with the expression of ATR, BRCA1, and BRCA2 genes and a moderately positive correlation with ATM expression (R=0.47). Immunohistochemical analysis showed significantly lower levels of KMT2C, ATM, ATR, and BRCA2 expression in H-FLACs than in common adenocarcinomas, and a trend of lower BRCA1 levels. Additionally, KMT2C expression showed a weak to moderate correlation with that of ATM, ATR, BRCA1, and BRCA2.

Conclusions

Cancers containing H-FLAC components showed lower levels of KMT2C and HRR factors than common lung adenocarcinomas, and their levels exhibited a positive correlation. These results support the hypothesis that loss of KMT2C function decreases the expression of the HRR factors in H-FLACs. H-FLACs with low KMT2C expression may be a good indication for poly (ADP-ribose) polymerase (PARP) inhibitor-based therapy.

SWI/SNF complex gene variations are associated with a higher tumor mutational burden and a better response to immune checkpoint inhibitor treatment: a pan-cancer analysis of next-generation sequencing data corresponding to 4591 cases

Background

Genes related to the SWItch/sucrose nonfermentable (SWI/SNF) chromatin remodeling complex are frequently mutated across cancers. SWI/SNF-mutant tumors are vulnerable to synthetic lethal inhibitors. However, the landscape of SWI/SNF mutations and their associations with tumor mutational burden (TMB), microsatellite instability (MSI) status, and response to immune checkpoint inhibitors (ICIs) have not been elucidated in large real-world Chinese patient cohorts.

Methods

The mutational rates and variation types of six SWI/SNF complex genes (ARID1A, ARID1B, ARID2, SMARCA4, SMARCB1, and PBRM1) were analyzed retrospectively by integrating next-generation sequencing data of 4591 cases covering 18 cancer types. Thereafter, characteristics of SWI/SNF mutations were depicted and the TMB and MSI status and therapeutic effects of ICIs in the SWI/SNF-mutant and SWI/SNF-non-mutant groups were compared.

Results

SWI/SNF mutations were observed in 21.8% of tumors. Endometrial (54.1%), gallbladder and biliary tract (43.4%), and gastric (33.9%) cancers exhibited remarkably higher SWI/SNF mutational rates than other malignancies. Further, ARID1A was the most frequently mutated SWI/SNF gene, and ARID1A D1850fs was identified as relatively crucial. The TMB value, TMB-high (TMB-H), and MSI-high (MSI-H) proportions corresponding to SWI/SNF-mutant cancers were significantly higher than those corresponding to SWI/SNF-non-mutant cancers (25.8 vs. 5.6 mutations/Mb, 44.3% vs. 10.3%, and 16.0% vs. 0.9%, respectively; all p  < 0.0001). Furthermore, these indices were even higher for tumors with co-mutations of SWI/SNF genes and MLL2/3. Regarding immunotherapeutic effects, patients with SWI/SNF variations showed significantly longer progression-free survival (PFS) rates than their SWI/SNF-non-mutant counterparts (hazard ratio [HR], 0.56 [95% confidence interval {CI} 0.44–0.72]; p < 0.0001), and PBRM1 mutations were associated with relatively better ICI treatment outcomes than the other SWI/SNF gene mutations (HR, 0.21 [95% CI 0.12–0.37]; p = 0.0007). Additionally, patients in the SWI/SNF-mutant + TMB-H (HR, 0.48 [95% CI 0.37–0.54]; p  < 0.0001) cohorts had longer PFS rates than those in the SWI/SNF-non-mutant + TMB-low cohort.

Conclusions

SWI/SNF complex genes are frequently mutated and are closely associated with TMB-H status, MSI-H status, and superior ICI treatment response in several cancers, such as colorectal cancer, gastric cancer, and non-small cell lung cancer. These findings emphasize the necessity and importance of molecular-level detection and interpretation of SWI/SNF complex mutations.

A case report of low grade fetal lung adenocarcinoma with TP53 mutation

RATIONALE

Fetal lung adenocarcinoma (FLAC) is a rare malignant tumor that occurs in the alveolar epithelium. FLAC, as a distinct entity, is a malignancy with a very low incidence, accounting for less than 0.5% of all lung tumors, with a high rate of misdiagnosis due to its rarity, lack of typical presentation and imaging signs. According to histopathological differences, FLAC is further divided into 2 types: low-grade FLAC and high-grade FLAC. In the article, we report a young woman who was diagnosed with low-grade fetal-type lung adenocarcinoma.

PATIENT CONCERNS

An 18-year-old female patient was admitted due to cough and chest distress.

DIAGNOSIS

The final pathological examination confirmed that the lesion was a low-grade fetal lung adenocarcinoma.

INTERVENTIONS

The patient underwent thoracoscopic left lower lobectomy and regional lymph node dissection.

OUTCOMES

The postoperative course was stable, and no recurrence was observed 1 year after operation.

LESSONS

To the best of our knowledge, there are no previous case reports of low-grade fetal-type adenocarcinoma, TP53 gene mutation, and the significance of its mutation is not extensively studies. FLAC, although extremely rare, is considered in the differential diagnosis of lung cancer. In addition, biopsy, histopathology, and specific immunohistochemical staining of larger tissue specimens are helpful for accurate diagnosis of FLAC.

Morphological and Molecular Characteristics in Low Grade Fetal Adenocarcinoma of the Lung: Two Case Reports and Literature Review

Background: Low-grade fetal adenocarcinoma of the lung is a rare pulmonary tumor resembling fetal lung histologically. Due to its rarity, there is limited information regarding the pathogenesis and biological characteristics of low-grade fetal adenocarcinoma of the lung. Here, we describe two cases of low-grade fetal adenocarcinoma of the lung treated at our hospital and summarize cases of low-grade fetal adenocarcinoma of the lung reported in the literature. Case presentation: We examined two cases (one woman and one man; 30 and 67 years old, respectively). Histologically, tumor tissues from both cases had a complex glandular component with clear cuboidal and columnar cells that resembled the histological features of fetal lung. In some areas, squamous morules were prominent. Immunohistochemically, nuclear/cytoplasmic expression of β-catenin was detected in both cases. Mutation analysis revealed a CTNNB1 mutation in both cases and a DICER1 mutation in 1 case. No mutations in EGFR, BRAF, KRAS, or PIK3CA were found. Conclusions: Low-grade fetal adenocarcinoma of the lung showed a high frequency of CTNNB1 mutations and low frequencies of EGFR, KRAS, BRAF, and PIK3CA mutations in our examined cases and in previous studies. This rare tumor has unique clinicopathological characteristics with specific genetic aberrations involving the Wnt pathway. These results provide a molecular basis for development of new therapies to treat these tumors.

Distinct properties of pure- and mixed-type high-grade fetal lung adenocarcinomas by genetic profiling and transcription factor expression

The clinicopathological differences among high-grade fetal lung adenocarcinomas completely comprising tumor cells that resemble fetal lung epithelium (pure type) and those with fetal lung-like components admixed with conventional adenocarcinoma cells (mixed type) remain undetermined. Here, we examined the clinicopathological, immunohistochemical, and molecular features of 11 lung adenocarcinomas with fetal lung-like morphology among 3895 consecutive cases of primary lung cancer based on the expression pattern of transcription factors. According to the current WHO classification, two cases (0.05%) were categorized as low-grade fetal adenocarcinoma, two cases (0.05%) were pure-type high-grade fetal adenocarcinoma, five cases (0.1%) were mixed-type high-grade fetal adenocarcinoma, and the remaining two cases (0.05%) were lung adenocarcinoma with high-grade fetal features (fetal lung-like morphology occupied less than 50%). CTNNB1 mutations were exclusively identified in low-grade fetal adenocarcinomas. In contrast, mixed-type high-grade fetal adenocarcinoma or lung adenocarcinoma with high-grade fetal features frequently harbored mitogenic drivers including EGFR mutations. Furthermore, almost all tumor cells expressed CDX2 and HNF4α in both cases of pure-type high-grade fetal lung adenocarcinoma, but lacked TTF-1 positivity. In contrast, TTF-1 was frequently expressed in mixed-type high-grade fetal lung adenocarcinoma and in lung adenocarcinoma with high-grade fetal features. Our data suggest similar prevalence of low-grade fetal lung adenocarcinoma and pure-type high-grade fetal lung adenocarcinoma, and indicate that pure- and mixed-type high-grade fetal lung adenocarcinomas are distinct, with the former akin to low-grade fetal adenocarcinoma with respect to purely embryonic morphology and absence of common lung adenocarcinoma mitogenic drivers, and the latter being genetically and transcriptionally related to conventional lung adenocarcinoma.