Clinicopathological, immunohistochemical, and mutational analyses of pulmonary enteric adenocarcinoma: usefulness of SATB2 and β -catenin immunostaining for differentiation from metastatic colorectal carcinoma

Double the trouble: pulmonary enteric adenocarcinoma with synchronous contralateral pulmonary adenocarcinoma

Pulmonary enteric adenocarcinoma (PEAC) is a rare subtype of non-small cell lung cancer with morphological and immunohistochemical features that are nearly indistinguishable from those of metastatic colorectal carcinoma. Owing to these overlapping features, diagnosis and treatment of PEAC can present a clinical challenge. We report the case of a 78-year-old man with synchronously diagnosed locally advanced pulmonary adenocarcinoma of the left lower lobe and localized right lower lobe PEAC. These malignancies exhibited distinct tumor molecular profiles and differed in their kinetic response to chemoimmunotherapy. We describe plausible mechanisms by which two distinct pulmonary malignancies are present in the contralateral lobes. To the best of our knowledge, this is the first reported case of synchronous invasive pulmonary adenocarcinoma and PEAC.

Lung enteric-type adenocarcinoma with gastric metastasis: a rare case report and literature review

Lung enteric-type adenocarcinoma (ETAC) is a rare subtype of non-small cell lung cancer (NSCLC), comprising approximately 0.6% of all primary lung adenocarcinomas. It is characterized by a tendency for early metastasis and a prognosis comparable to that of common lung adenocarcinoma. This case report described a patient with lung-ETAC who developed gastric metastasis. The patient underwent treatment with chemotherapy and a PD-1 inhibitor, resulting in disease remission with a progression-free survival (PFS) of 8 months. The follow-up time was 13 months. This case report was aimed to enhance understanding of the biological behavior of this rare tumor and provide insights into potential future treatment strategies.

Case report: 18F-FDG PET/CT in pulmonary enteric adenocarcinoma

Pulmonary enteric adenocarcinoma (PEAC), an uncommon variant of lung cancer, presents significant diagnostic challenges due to its overlapping characteristics with colorectal adenocarcinomas. We present a case of a 55-year-old non-smoking female patient diagnosed with PEAC. The patient's initial symptoms included fever, cough, and sputum production, with air space consolidation on CT, leading to an initial diagnosis of pneumonia. Sputum culture after admission showed no growth of bacteria and fungi. Anti-inflammatory therapy was not ideal. Subsequent bronchoscopy with endobronchial ultrasound and biopsy confirmed the diagnosis of PEAC. Gastroscopy and colonoscopy yielded negative results, and a PET/CT scan revealed an FDG-avid lesion in the right middle lobe, with no other significant hypermetabolic gastrointestinal lesions, thereby excluding an extrapulmonary primary gastrointestinal malignancy. The patient was ultimately staged as PEAC (T4N1M0, stage IIIb). She declined anti-tumor therapy and experienced clinical deterioration during follow-up. This case report expands the radiological spectrum of PEAC, adds to the limited literature, and emphasizes the role of 18F-FDG PET/CT in diagnosing such diseases. It also underscores the importance of a multidisciplinary approach in the management of PEAC.

The utility of the lineage specific immunohistochemical stains SATB2, CDX2, and villin, and the mucin glycoproteins MUC2, MUC5AC, and MUC6 to distinguish pulmonary invasive mucinous adenocarcinoma from metastatic colorectal carcinoma

CONTEXT

The lungs are a common site of tumor metastasis. While morphology and immunophenotype can help differentiate primary from metastatic tumors, distinguishing pulmonary invasive mucinous adenocarcinoma (PIMA) from metastatic colorectal adenocarcinoma (CRC) may occasionally be challenging due to overlapping morphological and immunohistochemical features. Lineage-specific markers such as CDX2, TTF-1, and napsin A are helpful with pulmonary non-mucinous adenocarcinoma (PNMA), however they are non-specific and insensitive when applied to PIMA. SATB2 is a newer marker that distinguishes CRC from upper gastrointestinal and pancreaticobiliary tumors; its utility in distinguishing CRC from PIMA has not been fully elucidated.

OBJECTIVE

To evaluate the performance of lineage-specific and mucin glycoprotein immunostains in distinguishing PIMA and CRC.

DESIGN

We stained tissue microarrays comprising 34 PNMA, 31 PIMA, and 32 CRC with CK7, CK20, SATB2, CDX2, villin, TTF-1, napsin A, and gel-forming mucins MUC2, MUC5AC, and MUC6.

RESULTS

PIMA showed significant (>50% of cells) expression of SATB2 (6%), CDX2 (6%), villin (74%), TTF-1 (13%), and napsin A (23%). However, significant CK7 expression was seen in nearly all PIMA (30/31) and none of the metastatic CRC.

CONCLUSION

Our results suggest that CK7 remains one of the most useful markers for distinguishing primary PIMA from metastatic CRC. Expression of the mucin glycoproteins MUC5AC and MUC6 and lack of expression of MUC2 favored a diagnosis of PIMA, but expression of these markers was too heterogeneous to be of clinical utility. To our knowledge this is the only study comparing the immunohistochemical profile of PIMA and metastatic CRC in lung metastasectomy specimens.

Proteomics-Derived Biomarker Panel Facilitates Distinguishing Primary Lung Adenocarcinomas With Intestinal or Mucinous Differentiation From Lung Metastatic Colorectal Cancer

The diagnosis of primary lung adenocarcinomas with intestinal or mucinous differentiation (PAIM) remains challenging due to the overlapping histomorphological, immunohistochemical (IHC), and genetic characteristics with lung metastatic colorectal cancer (lmCRC). This study aimed to explore the protein biomarkers that could distinguish between PAIM and lmCRC. To uncover differences between the two diseases, we used tandem mass tagging-based shotgun proteomics to characterize proteomes of formalin-fixed, paraffin-embedded tumor samples of PAIM (n = 22) and lmCRC (n = 17).Then three machine learning algorithms, namely support vector machine (SVM), random forest, and the Least Absolute Shrinkage and Selection Operator, were utilized to select protein features with diagnostic significance. These candidate proteins were further validated in an independent cohort (PAIM, n = 11; lmCRC, n = 19) by IHC to confirm their diagnostic performance. In total, 105 proteins out of 7871 proteins were significantly dysregulated between PAIM and lmCRC samples and well-separated two groups by Uniform Manifold Approximation and Projection. The upregulated proteins in PAIM were involved in actin cytoskeleton organization, platelet degranulation, and regulation of leukocyte chemotaxis, while downregulated ones were involved in mitochondrial transmembrane transport, vasculature development, and stem cell proliferation. A set of ten candidate proteins (high-level expression in lmCRC: CDH17, ATP1B3, GLB1, OXNAD1, LYST, FABP1; high-level expression in PAIM: CK7 (an established marker), NARR, MLPH, S100A14) was ultimately selected to distinguish PAIM from lmCRC by machine learning algorithms. We further confirmed using IHC that the five protein biomarkers including CDH17, CK7, MLPH, FABP1 and NARR were effective biomarkers for distinguishing PAIM from lmCRC. Our study depicts PAIM-specific proteomic characteristics and demonstrates the potential utility of new protein biomarkers for the differential diagnosis of PAIM and lmCRC. These findings may contribute to improving the diagnostic accuracy and guide appropriate treatments for these patients.

Clinicopathological and genetic analyses of pulmonary enteric adenocarcinoma

AIMS

Pulmonary enteric adenocarcinoma (PEAC) is a rare variant of pulmonary adenocarcinoma. Due to its rarity, few pathological and molecular studies have been performed on PEAC. We herein conducted clinicopathological, immunohistochemical and molecular analyses of PEAC with a focus on its differentiation from invasive mucinous adenocarcinoma (IMA).

METHODS

We examined the clinicopathological features of 16 cases of PEAC and performed a genetic analysis using next-generation sequencing (NGS). The results obtained were compared with those for IMA.

RESULTS

The average age of patients with PEAC (seven men and nine women) was 72.9 years. A comparison of clinical data on PEAC and IMA revealed no significant differences in age, sex or smoking history. Fifteen PEAC cases had dirty necrosis. Immunohistochemically, the positive rates for each antibody in PEAC were as follows: CK7, 88% (14/16); CK20, 81% (13/16); CDX2, 88% (14/16); p53, 69% (11/16); MUC1, 100% (16/16); MUC2, 19% (3/16); MUC5AC, 69% (11/16); MUC6, 19% (3/16). The positive rates for these antibodies in IMA were 100%, 87%, 0%, 7%, 93%, 0%, 100% and 80%, respectively. EGFR mutations, the MET exon 14 skipping mutation, BRAF mutations, the ALK fusion gene and ROS-1 fusion gene were not detected in any cases of PEAC or IMA. Among PEAC cases, NGS identified KRAS mutations in seven (44%, 7/16) and TP53 mutations in nine (56%, 9/16). Among IMA cases, the most commonly mutated gene was KRAS (90%).

CONCLUSIONS

The rates of dirty necrosis, immunopositivity for CDX2 and TP53 mutations were significantly higher, while that of KRAS mutations was significantly lower in PEAC cases than in IMA cases.

Development and validation of a decision tree for distinguishing pulmonary adenocarcinomas with mucinous features and metastatic colorectal adenocarcinoma

BACKGROUND

Diagnosis of mucinous carcinomas in the lung on transbronchial biopsy or fine-needle aspiration (FNA) samples can be difficult for the pathologist, because primary and metastatic tumors can have similar morphological, immunohistochemical, and molecular characteristics. Correct diagnosis is key to determine appropriate therapy and to distinguish primary from metastatic disease. This distinction often falls to the pathologist in patients with a history of mucinous adenocarcinoma of the colon. Despite its drawbacks, immunohistochemistry is often employed to help assign a primary site for mucinous adenocarcinomas in the lung. However, the published data in this regard is limited to studies that use only a handful of markers.

METHODS

The authors examined the staining characteristics and heterogeneity of CK7, TTF-1, NapsinA, CK20, CDX2, and SATB2 in resection specimens of pulmonary adenocarcinomas with mucinous features and metastatic colorectal adenocarcinoma.

RESULTS

Based on the heterogeneity, sensitivity, and specificity in this cohort, the authors developed a decision tree based on TTF-1, SATB2, CDX2, and CK7 to categorize tumors as primary or metastatic lesions. Validation of the decision tree in FNA specimens from the lungs and lung-draining lymph nodes showed 84% concurrence in cases from the lung and 100% concurrence in cases from the lymph node. In cases where the algorithm assigned a primary site, it was 95% accurate compared to the multidisciplinary diagnosis.

CONCLUSIONS

This method holds promise in distinguishing primary versus metastatic lesions in resection, biopsy, and FNA samples from the lungs.

Frequent nuclear β-catenin expression in pulmonary enteric-type adenocarcinoma according to the current World Health Organization criteria

Based on the current World Health Organization classification criteria, five of 3895 consecutive cases of surgically resected primary lung carcinomas (0.13%) categorized as enteric-type were analyzed. Three cases completely comprised tumor cells that resemble colorectal adenocarcinoma, while the other two cases exhibited features of conventional adenocarcinomas admixed with enteric components. Immunohistochemically, all patients expressed at least three of the five intestinal markers: CDX2, CK20, HNF4α, MUC2, and SATB2. None of the patients expressed TTF-1 and NKX3.1. Three cases showed nuclear accumulation of β-catenin, indicating activation of the Wnt/β-catenin signaling pathway; APC mutations were detected in one of these cases. TP53 mutations were detected in three cases. Mutated EGFR or ALK fusions were not detected. Our study demonstrates that pulmonary enteric-type adenocarcinomas share immunohistochemical features and genetic alterations with colorectal adenocarcinomas, which are characterized by frequent activation of the Wnt/β-catenin signaling pathway and a lack of actionable mutations.

Deciphering Lung Adenocarcinoma Heterogeneity: An Overview of Pathological and Clinical Features of Rare Subtypes

Lung cancer is one of the most frequently diagnosed cancers worldwide and the leading cause of cancer-related death. The 2021 World Health Organization (WHO) classification provided a detailed and updated categorization of lung adenocarcinomas with a special focus on rare histological types, including enteric, fetal and colloid types, as well as not otherwise specified adenocarcinoma, overall accounting for about 5-10% of all cases. However, rare entities are nowadays difficult to diagnose in most centers, and evidence of optimal therapeutic management for these patients is still lacking. In recent years, increasing knowledge about the mutational profile of lung cancer, in addition to the spreading diffusion of next-generation sequencing (NGS) in different centers, have been helpful in the identification of rare variants of lung cancer. Hence, the hope is that several new drugs will be available in the near future to treat these rare lung tumors, such as in targeted therapy and immunotherapy, which are often used in clinical practice for several malignancies. The aim of this review is to summarize the current knowledge about the molecular pathology and clinical management of the most common rare adenocarcinoma subtypes in order to provide a concise and updated report that can drive clinicians' choices in their routine practice.

Clinical presentation and outcome of patients with enteric-type adenocarcinoma of the lung: A pooled analysis of published cases

Enteric-type adenocarcinoma of the lung (lung-ETAC, former pulmonary enteric adenocarcinoma, PEAC) is a rare subtype of non-small cell lung cancer (NSCLC), which shares morphological and immunohistochemical features with lung and colorectal adenocarcinoma. Few data are available on patient prognosis, possible prognostic factors and systemic approach to metastatic disease. We performed a pooled analysis and a systematic review of published lung-ETAC, along with an additional case description. Thirty-one eligible publications were identified, providing data from 126 patients. In the 127 patients overall analyzed, median overall survival (OS) was 56.0 (range 36.7-75.3) months in early-stage patients and 14.0 (range 4.5-23.5) months in those with advanced/metastatic disease. Median disease-free survival (DFS) after radical surgery was 24 (range 22.6-35.1) months. Smoking status (HR 4.304, 95% CI: 1.261-14.693, p = 0.020) and node involvement (HR 1.853, 95% CI: 1.179-2.911, p = 0.007) were the negative independent prognostic factors at multivariate analysis. As regards systemic therapies for advanced cases, no firm conclusions were drawn about the efficacy of lung cancer-oriented chemotherapy regimens as opposed to colon cancer-oriented ones. Molecular analysis of lung-ETAC revealed a relatively high mutational rate, with alterations in several druggable molecular pathways, KRAS and NRAS (31%) were the most frequently mutated oncogenes, followed by ROS1 (15%), RET (13%), BRAF (11%), EGFR (8%) and ALK (6%). Moreover, 3 (15%) out of 20 cases showed DNA mismatch repair deficiency (dMMR). In conclusion, advanced lung-ETAC patients appeared to have a better prognosis compared to other subtypes of NSCLC. Moreover, the mutational rate and microsatellite instability found in lung-ETACs suggest that a significant proportion of these patients could benefit from target therapies and immunotherapy.

Thyroid transcription factor-1 expression in rectal adenocarcinoma metastatic to the lung

Distinguishing metastatic lung tumors from primary lung cancer is essential for planning the appropriate treatment strategy. Thyroid transcription factor-1 (TTF-1) is a reliable immunohistochemistry (IHC) marker for differentiating between primary lung adenocarcinomas and metastatic lung tumors originating from colorectal adenocarcinomas. Herein, we report a rare case of TTF-1 expression in both the metastatic lung tumor and primary rectal adenocarcinoma. Aside from the similar histological characteristics of both tumors when stained with hematoxylin-eosin, the IHC patterns, including negative results for alveolar epithelium markers (napsin A and CK7) and positive results for intestinal markers (CK20, CDX2, SATB2, and β-catenin), of the lung tumor and the primary rectal adenocarcinoma strongly supported the final diagnosis. Considering the non-negligible frequency of TTF-1 positivity in colorectal adenocarcinomas, applying the IHC panel including multiple markers for alveolar epithelium and intestinal differentiation, would be helpful to support the diagnosis of metastatic lung tumor from a rectal adenocarcinoma.

A pulmonary enteric adenocarcinoma patient harboring a rare EGFR exon 19 P753S mutation: Case report and review

Pulmonary enteric adenocarcinoma (PEAC) is a rare subtype of non–small cell lung cancer (NSCLC), accounting for about 0.6% of all primary lung adenocarcinoma. Although epidermal growth factor receptor (EGFR) mutation is common in primary lung adenocarcinoma, it is rarely reported in PEAC. This case report describes a PEAC patient with co-mutations of EGFR, Kirsten rat sarcoma viral oncogene (KRAS), and TP53, being treated with immunotherapy combined with chemotherapy. A 69-year-old man complained of cough and expectoration with bloody sputum for 2 weeks. The lung-enhanced CT scan showed a massive soft tissue shadow, about 46 × 35 mm in the lower lobe of the right lung. The neoplasm sample in the lower lobe of the right lung was obtained using CT-guided fine-needle aspiration (FNA). Immunohistochemical assays showed that the tumor was positive for CK7, CDX-2, C-MET, and villin. Gastroscopy and rectal colonoscopy had been performed respectively to exclude a diagnosis of colorectal adenocarcinoma. The patient was finally diagnosed with pulmonary intestinal adenocarcinoma. Next-generation sequencing (NGS) analysis showed a rare EGFR exon 19 missense mutation (c.2257C>T, p.P753S), KRAS exon 2 missense mutation (c.35G>T, p.G12V), and TP53 exon 5 missense mutation (c.401T>C, p.F134S). The lung-enhanced CT scan showed that the tumor shrank after four cycles of chemotherapy combined with immunotherapy. We hope that this case report can increase the understanding of this rare type of tumor and provide new molecular indications for diagnosis and individualized treatment. Furthermore, the combination of chemotherapy and immunotherapy seems to be an effective therapy for PEAC. Whether the use of immunotherapy can provide clinical benefits needs to be further explored with more samples in future studies.

Genomic and epigenomic profiles distinguish pulmonary enteric adenocarcinoma from lung metastatic colorectal cancer

BACKGROUND

As a rare subtype of lung adenocarcinoma, the diagnosis of pulmonary enteric adenocarcinoma (PEAC) remains challenging due to overlapping morphologic spectrum with lung metastatic colorectal cancer (lmCRC). However, the molecular features of PEAC as a separate lung cancer entity are poorly understood.

METHODS

We performed whole-exome sequencing and targeted bisulfite sequencing of 32 PEAC and 30 lmCRC to improve differential molecular characterization of the two diseases. We used machine learning methods to select key markers and developed a diagnostic classifier. In addition, we validated the classifier in the internal test cohort and an independently recruited external validation cohort with 17 PEAC and 7 lmCRC.

FINDINGS

Our results showed that EGFR was the key driver mutation in PEAC but at a lower prevalence compared to typical lung adenocarcinomas, whereas ERBB2 and KRAS were more frequently observed in PEAC. By contrast, we observed significant enrichment of KRAS and APC mutations in lmCRC compared with PEAC. At the chromosome arm level, copy number variations in 13q, 14q, and 18p were the major chromosomal differences observed between PEAC and lmCRC. Furthermore, by comparing differentially methylated regions (DMRs), we established a neat DNA methylation-based classifier consisting of eight DMRs. This classifier correctly classified all samples in the training cohort and 95% of the samples in the internal test cohort. An external validation cohort of 24 cases recruited from multiple centers in China also reliably agreed with pathological diagnosis.

INTERPRETATION

These results provide solid evidence of PEAC-specific genomic characteristics and demonstrate the potential utility of DNA methylation markers for auxiliary diagnosis of PEAC and lmCRC.

FUNDING

This work was supported by National key research and development project 2019YFC1315700, CAMS Key Laboratory of Translational Research on Lung Cancer (2018PT31035), and Beijing Natural Science Foundation (7222144).

Genetic mutation profiles and immune microenvironment analysis of pulmonary enteric adenocarcinoma

BACKGROUND

Pulmonary enteric adenocarcinoma (PEAC) has distinctive clinical outcomes, radiographic, pathological and molecular characteristics. The prognosis of patients with PEAC was poor. However, molecular profiles and therapeutic biomarkers of PEAC remain elusive.

METHODS

In the present study, the hospitalized patients with PEAC admitted to Tongji Hospital in Wuhan from January 1, 2014 to November 20, 2020 were retrospectively enrolled and followed until December 10, 2020. Comprehensive genomic profiling of tumor tissue from the PEAC patients were performed and compared with lung adenocarcinoma, colorectal cancer and metastatic colorectal carcinoma. Tumor immune microenvironment analysis were evaluated.

RESULTS

There were 10 patients with PEAC enrolled. 70% of patients were male and the median age of onset was 63 years (interquartile range, 55-72). There were six early-stage patients (Stage IA to IIB) and four stage IV patients. Molecular analysis revealed the most common gene mutations included TP53 (57%, 4/7) and KRAS (57%, 4/7) mutations. There were 40% mutations occurred in genes encoding receptor tyrosine kinases (RTKs). 100% of patients (8/8) were microsatellite stability (MSS). The median level of TMB was 6.0 (interquartile range, 4.5-7.0) mutations/Mb. Three of 10 patients showed low PD-L1 expression (tumor proportion score < 10%) and the others were PD-L1 negative. A small subset of CD8+, CD3+, CD68+ T cells were observed and were mainly distributed in the cancer stroma.

CONCLUSION

This study demonstrated that PEAC was characterized by low-frequency RTK gene mutation, high KRAS mutation, low PD-L1 expression, low TMB, and low CD8+ T cells infiltration.

Expression of nSATB2 in Neuroendocrine Carcinomas of the Lung: Frequent Immunopositivity of Large Cell Neuroendocrine Carcinoma with a Diagnostic Pitfall

Small cell lung carcinoma (SCLC) and pulmonary large cell neuroendocrine carcinoma (LCNEC) are both classified as lung neuroendocrine carcinoma (NEC). It has recently been reported that the special AT-rich sequence-binding protein 2 (STAB2), known as a colorectal cancer marker, is also expressed in NECs occurring in various organs including the lung. However, few studies have examined any differences of SATB2 immunopositivity between SCLC and LCNEC. We investigated SATB2 expression in 45 SCLC and 14 LCNEC cases using immunohistochemistry as well as the expression of caudal-type homeobox 2 (CDX2) and keratin (KRT) 20. The LCNEC cases were more frequently positive for SATB2 (ten out of 14, 71%) than the SCLC ones (seventeen out of 45, 38%) with a statistically significance (P = 0.035). Furthermore, two LCNEC cases were positive for CDX2 while no positive findings were observed for any SCLC cases, the difference of which, however, was not statistically significant (P = 0.053). KRT20 was negative in all LCNEC and SCLC cases. These results require our attention when we use SATB2 and CDX2 as colorectal cancer markers because their expression in pulmonary NECs can lead to a misdiagnosis that the tumor is of metastatic colorectal adenocarcinoma, especially when the patient has a past history of colorectal cancer. Analyzing the relationship between the demographic/clinical variables and the SATB2 expression in the SCLC cases, just high Brinkman index (≥ 600) was significantly related to the positivity of SATB2 (P = 0.017), which is interesting considering the strong relationship between SCLC and smoking.

Diagnosis and treatment of primary pulmonary enteric adenocarcinoma: Report of Six cases

BACKGROUND

Primary pulmonary enteric adenocarcinoma (PEAC) is a very rare subtype of invasive adenocarcinoma, and there have been no large studies on PEAC to date. Therefore, it is necessary to obtain much more information about the clinical and pathological features, diagnosis, differential diagnosis, and treatment of PEAC.

CASE SUMMARY

All clinical data of six patients with confirmed PEAC from 2013 to 2018 were collected, and data on diagnosis, differential diagnosis, and treatment of PEAC are discussed combined with all the associated literature. The mean age of six patients was 64.0 ± 5.6 (59-73) years old. Their clinical manifestations were heterogeneous, and during their disease course, there were no gastrointestinal symptoms. There was no evidence from colonoscopy or imaging studies to suggest digestive tract tumors or new metastases. The most commonly mutated gene was KRAS (50.0%), and the pathological features of the six cases were similar to those of colorectal cancer. CDX2 (83.3%) and CK7 (66.7%) had the highest positive rates upon immunohistochemical examination. In the associated literature, 252 cases were identified, and the most commonly mutated gene was KRAS (42.9%). Additionally, CDX2 (68.3%) and CK7 (85.8%) had the highest positive rates. Patients mainly received surgery, chemotherapy, and radiotherapy, immunotherapy was not included.

CONCLUSION

Positive results for CDX2 and CK7 play an important role in the diagnosis and differential diagnosis of PEAC, and immunotherapy or targeted therapy focused on KRAS needs to be further studied for the treatment of PEAC.

Pulmonary enteric adenocarcinoma

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Synthetically expounded the clinical characteristics of PEAC.

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Systematically described the differentiation of PEAC from primary lung adenocarcinoma and MCRC.

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Found patients with PEAC may have high frequencies of HER2 and MMR mutations.

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Proposed a new conjecture that patients with PEAC might benefit from anti-HER2 therapy and immune checkpoint inhibitors.

Pulmonary enteric adenocarcinoma (PEAC) is an exceptionally rare subtype of non–small cell lung cancer (NSCLC). It is characterized by pathological features similar to those of colorectal adenocarcinoma. Most patients with PEAC have almost no special clinical manifestations, and it is often difficult to differentiate from metastatic colorectal adenocarcinoma (MCRC). As a special type of lung adenocarcinoma, PEAC has unique mutation expression and immune characteristics; its mutation profile shows higher Kirsten rat sarcoma viral oncogene (KRAS), human epidermal growth factor receptor-2 (HER2) , DNA mismatch repair(MMR) mutation rates, and much lower epidermal growth factor receptor (EGFR) rate. So in the future, targeted therapy may tend to be a new light in the treatment of PEAC. As for immunohistochemistry (IHC), CDX-2, villin, and CK7 are significantly positive in PEAC. This review focuses on the pathologic features, immunohistochemical examination, mutation analysis, diagnosis, treatment, and prognosis of PEAC.

SATB2 in Neoplasms of Lung, Pancreatobiliary, and Gastrointestinal Origins

OBJECTIVES

Special AT-rich binding protein 2 (SATB2) immunohistochemistry (IHC) has high sensitivity and specificity for colorectal adenocarcinoma (CRC), but data on its expression in specific subsets of pulmonary, gastric, small bowel, and pancreatobiliary adenocarcinomas (ADCAs) are relatively limited or discordant. We assessed SATB2 expression in a large cohort of ADCAs from these sites to determine its reliability in distinguishing CRC from them.

METHODS

SATB2 IHC was performed on 335 neoplasms, including 40 lung ADCAs, 165 pancreatobiliary neoplasms (34 intraductal papillary mucinous neoplasms [IPMNs], 19 pancreatic ADCAs, 112 cholangiocarcinomas [CCs]), and 35 gastric, 13 small bowel, 36 ampullary (AMP), and 46 CRC ADCAs. The cases were evaluated for positivity (defined as ≥5% nuclear staining), and an H-score was calculated based on the percentage of SATB2+ cells and staining intensity. Analysis was performed to determine the optimal H-score threshold to separate CRC and non-CRC.

RESULTS

SATB2 was positive in 3% of lung, 2% of CC, 17% of gastric, 38% of small bowel, and 6% of AMP ADCAs. All pancreatic ADCA/IPMNs were negative, and 87% CRCs were positive.

CONCLUSIONS

SATB2 is not entirely specific for colorectal origin and can be expressed in a subset of gastrointestinal ADCAs. It is most useful in the differential of CRC vs lung and pancreatobiliary ADCAs.

Pulmonary enteric adenocarcinoma: a literature review

Pulmonary enteric adenocarcinoma (PEAC) is an extremely rare type of non-small cell lung cancer (NSCLC) with a histologic pattern that mimics metastatic colorectal cancer (MCC). The main clinical symptoms in PEAC patients are dyspnoea, coughing, hemoptysis, and chest and back pain. The first article about PEAC appeared in 1991 in the form of a case report. As a variant of invasive lung carcinoma, only a small number of case reports and clinical research studies have been carried out, and the only one guidance on diagnosis and treatment is the WHO Tumor Classification book. It is important for doctors to distinguish PEAC from MCC to extend survival time and improve the quality of life. We reviewed the existing literature regarding the diagnosis, treatment, and prognosis of PEAC to provide some valuable clinical references.

Clinicopathological and mutational differences between tumors with multiple metastases and single lung metastasis in colorectal cancer

Cancer metastasis, particularly multiple metastatic cancer, is a significant event that affects patient prognosis. However, single metastasis can be treated by partial resection, although the clinicopathological and molecular profile of single lung metastasis has not been thoroughly elucidated. The present study examined tumor heterogeneity by comparing the mutation status between primary colorectal cancer (CRC) and corresponding metastatic lesions to identify prognostic factors associated with single lung metastasis and multiple metastases. The present study enrolled 31 cases of CRC; 20 cases with multiple metastases and 11 cases with single lung metastasis. Clinicopathologically, all cases with multiple metastases were tubular adenocarcinoma, and 3/11 cases with single metastasis were mucinous adenocarcinoma originating from the left side, the remaining 8 cases were tubular adenocarcinoma from the left side. CRC cases with multiple metastases exhibited more frequent vascular invasion, but not lymphatic invasion, than those with single lung metastasis. Furthermore, CRC with multiple metastases was associated with strong tumor budding (P=0.04). Patients with CRC with multiple metastases had lower recurrence-free survival rates compared with those with single lung metastasis (P=0.02). However, there was no significant difference between these two groups in terms of overall survival rates. A next-generation sequencing cancer hotspot panel was used to analyze a heterochronous multiple metastases case, including brain metastasis. Sanger sequencing, immunohistochemistry and microsatellite instability were examined for all 31 cases to reveal the molecular features. KRAS and TP53 mutation signatures were largely preserved throughout the metastatic events. TP53/APC mutations and overexpression of p53 appeared to be associated with the presence of lymphovascular invasion and strong tumor budding, respectively, although these differences were not statistically significant. Early relapses in patients with CRC could be a sign for eventual multiple metastases, although these may not affect the overall survival of patients with CRC. Considerable mutational changes were seemingly rare during metastatic events in patients with CRC.

Pulmonary enteric adenocarcinoma: an overview

Most commonly described as sporadic, pulmonary adenocarcinoma with enteric differentiation (PAED) is a rare variant of invasive lung cancer recently established and recognised by the World Health Organization. This tumour is highly heterogeneous and shares several morphological features with pulmonary and colorectal adenocarcinomas. Our objective is to summarise current research on PAED, focusing on its immunohistochemical and molecular features as potential tools for differential diagnosis from colorectal cancer, as well as prognosis definition and therapeutic choice. PAED exhibits an 'entero-like' pathological morphology in more than half cases, expressing at least one of the typical immunohistochemical markers of enteric differentiation, namely CDX2, CK20 or MUC2. For this reason, this malignancy appears often indistinguishable from a colorectal cancer metastasis, making the differential diagnosis laborious. Although standard diagnostic criteria have not been established yet, in the past few years, a number of approaches have been addressed, aimed at defining specific immunohistochemical and molecular signatures. Based on previously published literature, we have collected and analysed molecular and immunohistochemical data on this rare neoplasm, and have described the state of the art on diagnostic criteria as well as major clinical and therapeutic implications.The analysis of data from 295 patients from 58 published articles allowed us to identify the most represented immunohistochemical and molecular markers, as well as major differences between Asian PAEDs and those diagnosed in European/North American countries. The innovative molecular approaches, exploring driver mutations or new gene alterations, could help to identify rare prognostic factors and guide future tailored therapeutic approaches to this rare neoplasm.

Next generation sequencing of lung adenocarcinoma subtypes with intestinal differentiation reveals distinct molecular signatures associated with histomorphology and therapeutic options

OBJECTIVES

We aim to provide a better understanding of the molecular landscape of primary lung adenocarcinomas with intestinal differentiation.

MATERIAL AND METHODS

Five invasive mucinous adenocarcinomas (IMA) and seven pulmonary enteric adenocarcinomas (PEAD) were included in this study. Furthermore, we analyzed six pulmonary colloid adenocarcinomas (CAD), including one primary tumor, one metastasis, and two sample pairs consisting of the primary colloid lung tumor and a matching metastasis and an acinar component, respectively. All samples were characterized using immunohistochemistry (TTF-1, CK7, CK20, CDX2, Ki-67, ALK and PD-L1) and a next generation sequencing panel covering 404 cancer-related genes (FoundationOne® gene panel).

RESULTS AND CONCLUSION

While Ki-67 expression was comparably low in IMA (range: 8-15%) and in primary CAD (range: 5-8%), we observed considerably higher proliferation rates in the non-colloid tumor compartment (16%) and metastases (72%) from CAD, as well as in the PEAD-group (36-71%). The overall tumor mutational burden was lowest in IMA (2.5 mutations per megabase), intermediate in CAD (5.8 mutations per megabase) and highest in PEAD (16.8 mutations per megabase). KRAS mutations were frequent in all three tumor subtypes, but TP53 mutations were mostly limited to PEAD. While chromosomal alterations were rare in IMA, we discovered MYC amplifications in three of four CAD. Comparing primary and metastatic CAD, we observed the acquisition of multiple mutations and chromosomal alterations. PEAD had a variety of chromosomal alterations, including two cases with RICTOR amplification. PD-L1 expression (20%, 50% and 80% of tumor cells) was limited to three PEAD samples, only. In conclusion, we provide a detailed insight into the molecular alterations across and within the different subtypes of pulmonary adenocarcinomas with intestinal differentiation. From a clinical perspective, we provide data on potential treatment strategies for patients with PEAD, including immunotherapy.

DNA methylation profiling reliably distinguishes pulmonary enteric adenocarcinoma from metastatic colorectal cancer

Pulmonary enteric adenocarcinoma is a rare non-small cell lung cancer subtype. It is poorly characterized and cannot be distinguished from metastatic colorectal or upper gastrointestinal adenocarcinomas by means of routine pathological methods. As DNA methylation patterns are known to be highly tissue specific, we aimed to develop a methylation-based algorithm to differentiate these entities. To this end, genome-wide methylation profiles of 600 primary pulmonary, colorectal, and upper gastrointestinal adenocarcinomas obtained from The Cancer Genome Atlas and the Gene Expression Omnibus database were used as a reference cohort to train a machine learning algorithm. The resulting classifier correctly classified all samples from a validation cohort consisting of 680 primary pulmonary, colorectal and upper gastrointestinal adenocarcinomas, demonstrating the ability of the algorithm to reliably distinguish these three entities. We then analyzed methylation data of 15 pulmonary enteric adenocarcinomas as well as four pulmonary metastases and four primary colorectal adenocarcinomas with the algorithm. All 15 pulmonary enteric adenocarcinomas were reliably classified as primary pulmonary tumors and all four metastases as well as all four primary colorectal cancer samples were identified as colorectal adenocarcinomas. In a t-distributed stochastic neighbor embedding analysis, the pulmonary enteric adenocarcinoma samples did not form a separate methylation subclass but rather diffusely intermixed with other pulmonary cancers. Additional characterization of the pulmonary enteric adenocarcinoma series using fluorescence in situ hybridization, next-generation sequencing and copy number analysis revealed KRAS mutations in nine of 15 samples (60%) and a high number of structural chromosomal changes. Except for an unusually high rate of chromosome 20 gain (67%), the molecular data was mostly reminiscent of standard pulmonary adenocarcinomas. In conclusion, we provide sound evidence of the pulmonary origin of pulmonary enteric adenocarcinomas and in addition provide a publicly available machine learning-based algorithm to reliably distinguish these tumors from metastatic colorectal cancer.

Evaluation of Carcinoma of Unknown Primary on Cytologic Specimens

Carcinoma of unknown primary is defined as metastatic carcinoma without a clinically obvious primary tumor. Determining the tissue of origin in carcinoma of unknown primary is important for site-directed therapy. Immunohistochemistry is the most widely used tool for the work-up of metastases, but molecular profiling assays are also available. This review provides an overview of immunohistochemical stains in the work-up of metastatic carcinoma, with a focus on newer site-specific markers, and discusses the role of gene expression profiling assays for determining tissue of origin. The utility of cytopathology specimens in the evaluation of carcinoma of unknown primary also is highlighted.

Distinctive features of immunostaining and mutational load in primary pulmonary enteric adenocarcinoma: implications for differential diagnosis and immunotherapy

Background

Primary pulmonary enteric adenocarcinoma (PEAC) is an extremely rare variant of invasive lung cancer. It is highly heterogeneous while shares some common morphologic and immunohistochemical features with usual pulmonary adenocarcinoma (PAC) and colorectal adenocarcinoma (CRAC), making the differential diagnosis difficult. At present there are only limited studies about distinctive features of primary PEAC and the results are often inconsistent.

Methods

We retrospectively analyzed total 129 primary PEACs and 50 CRACs that were published since 1991 or diagnosed in our centre. Among them eight typical samples of primary PEACs and usual PACs were detected by targeted exome sequencing.

Results

The combination of CK7⁺/CDX2⁺ acquires high sensitivity (71.3%) and specificity (82%) in differential diagnosis of PEACs from CRAC. The primary PEACs harbor a high incidence of KRAS mutation but almost absent of EGFR mutation. Moreover, compared with usual PACs, the primary PEACs have higher nonsynonymous tumor mutation burden and more frequent MMR mutation.

Conclusions

The combination of CK7⁺/CDX2⁺ immunostaining and the distinctive genetic signatures, including low incidence of sensitivity genes mutations and high tumor mutation burden, is an important supplementary to the clinical differential diagnosis of primary PEACs. Our findings thus have significant implications for development of individualized treatment strategy in these patients.

Role of conventional immunomarkers, HNF4-α and SATB2, in the differential diagnosis of pulmonary and colorectal adenocarcinomas

AIMS

Pulmonary (ADC) and colorectal (CRC) adenocarcinomas are frequent entities in pathological routine diagnostics. Whereas the differential diagnosis is usually straightforward based on histomorphology, it can be challenging in small biopsies. In general, CDX-2, CK20, Napsin-A and TTF-1 are recommended immunohistological markers in this scenario. Hepatocyte nuclear factor 4 alpha (HNF4-α) and special AT-rich sequence-binding protein 2 (SATB2) were described recently as promising additional markers, but comprehensive large-scale data are lacking so far. Therefore, we analysed the expression of these six markers in 1021 non-small-cell lung cancers (NSCLC), including 472 ADC as well as in 80 pulmonary metastases of CRC.

METHODS AND RESULTS

Tissue microarrays of NSCLC and pulmonary metastases of CRC were stained for CDX-2, CK20, HNF4-α, Napsin-A, SATB2 and TTF-1 and staining results were correlated with clinicopathological variables. ADC exhibited expression of CDX-2, CK20, HNF4-α, Napsin-A, SATB2 and TTF-1 in nine (2%), 21 (4%), 17 (4%), 345 (73%), 35 (7%) and 408 (86%) samples, while 80 CRC were positive in 79 (99%), 74 (93%), 77 (96%), no (0%), 78 (98%) and five (6%) cases, respectively.

CONCLUSIONS

In addition to conventional immunomarkers, HNF4-α and particularly SATB2 may be helpful in the differential diagnosis of pulmonary ADC and metastases of CRC.

CK7/CK20 Double-Negative Pulmonary Enteric Adenocarcinoma With Histopathological Evaluation of Transformation Zone Between Enteric Adenocarcinoma and Conventional Pulmonary Adenocarcinoma

We report a rare case of pulmonary enteric adenocarcinoma (PEA) exhibiting a immunohistochemical feature of CK7/CK20 double-negativity by evaluating the transformation zone between PEA and conventional pulmonary adenocarcinoma (CPA). A 75-year-old man was found to have a mass, 40 mm in diameter, in the right lower lobe on chest computed tomography, and underwent right lower lobectomy. Histologically, the tumor was composed of a PEA and CPA component. The dominant PEA component had medium to large complex glands with tall columnar cells with eosinophilic cytoplasm and brush-border. The CPA component comprised small to medium glands with cuboidal cells. Moreover, intermediate glands (INT), which had cuboidal to tall columnar cells, with morphological features between PEA and CPA, was also observed in the transformation area. Immunohistochemically, the PEA component was negative for CK7, CK20, and TTF-1, and positive for CDX2 and SATB2 (weak): the CPA component was negative for CK20, CDX2, and SATB2, and positive for CK7 and TTF-1: the INT were negative for SATB2, with intermingled positive signals for CK7, CK20, TTF-1, and CDX2. The final diagnosis was PEA based on the CPA component and not colorectal carcinoma. To distinguish CK7-negative PEA from metastatic colorectal carcinoma, careful examination for a CPA component is very useful along with clinical information. There are no reports that discuss about process of oncogenesis, de novo sequence or transformation from CPA of PEA. This is the first reported case of CK7/CK20 double-negative PEA, with analysis of the transformation zone between PEA and CPA components.