OBJECTIVE: Gastrointestinal medullary carcinoma is a rare histologic subtype of adenocarcinoma. As nonampullary small bowel medullary carcinomas (SB-MCs) are poorly characterized, we aimed to analyse their clinicopathologic and immunohistochemical features and to compare them with nonmedullary small bowel adenocarcinomas (NM-SBAs).
RESULTS: Surgically resected SBAs collected through the Small Bowel Cancer Italian Consortium were classified as SB-MCs (carcinomas with ≥50% of tumour fulfilling the typical histologic criteria of MC) or NM-SBAs. Immunohistochemistry for cytokeratin (CK)7, CK20, CDX2, programmed death-ligand 1 (PD-L1) and mismatch repair proteins was performed in both SB-MCs and NM-SBAs. SB-MCs were also tested for CK8/18, synaptophysin, SMARCB1, SMARCA2, SMARCA4, and ARID1A and for Epstein-Barr virus (EBV)-encoded RNAs by in-situ hybridization. MLH1 promoter methylation status was evaluated in MLH1-deficient cases. Eleven SB-MCs and 149 NM-SBAs were identified. One (9%) SB-MC was EBV-positive, while 10 (91%) harboured mismatch repair deficiency (dMMR). MLH1 promoter hypermethylation was found in all eight dMMR SB-MCs tested. Switch/sucrose nonfermentable deficiency was seen in two (18%) SB-MCs, both with isolated loss of ARID1A. Compared with NM-SBAs, SB-MCs exhibited an association with coeliac disease (P < 0.001), higher rates of dMMR (P < 0.001), and PD-L1 positivity by both tumour proportion score and combined positive score (P < 0.001 for both), and a lower rate of CK20 expression (P = 0.024). Survival analysis revealed a better prognosis of SB-MC patients compared to NM-SBA cases (P = 0.02).
CONCLUSIONS: SB-MCs represent a distinct histologic subtype, with peculiar features compared to NM-SBAs, including association with coeliac disease, dMMR, PD-L1 expression, and better prognosis.

UNASSIGNED: Small bowel adenocarcinoma (SBA) is a rare gastrointestinal malignancy with an increasing incidence and a high propensity for liver metastasis (LM). This study aimed to investigate the risk factors for synchronous LM and prognostic factors in patients with LM.
UNASSIGNED: Utilizing the Surveillance, Epidemiology, and End Results (SEER) database, this study analyzed data from 2,064 patients diagnosed with SBA between 2010 and 2020. Logistic regression was used to determine risk factors for synchronous LM. A nomogram was developed to predict the risk of LM in SBA patients, and its predictive performance was assessed through receiver operating characteristic (ROC) curves and calibration curves. Kaplan-Meier and Cox regression analyses were conducted to evaluate survival outcomes for SBA patients with LM.
UNASSIGNED: Synchronous LM was present in 13.4% of SBA patients (n = 276). Six independent predictive factors for LM were identified, including tumor location, T stage, N stage, surgical intervention, retrieval of regional lymph nodes (RORLN), and chemotherapy. The nomogram demonstrated good discriminative ability, with an area under the curve (AUC) of 83.8%. Patients with LM had significantly lower survival rates than those without LM (P < 0.001). Survival analysis revealed that advanced age, tumor location in the duodenum, surgery, RORLN and chemotherapy were associated with cancer-specific survival (CSS) in patients with LM originating from SBA.
UNASSIGNED: This study highlights the significant impact of LM on the survival of SBA patients and identifies key risk factors for its occurrence. The developed nomogram aids in targeted screening and personalized treatment planning.

We present the case of a 62-year-old man with a history of celiac disease and IgA deficiency, following a strict gluten-free diet that was admitted to our hospital for recurrent abdominal pain, fatigue and melena. Esophagogastroduodenoscopy and colonoscopy with biopsies were normal. A video-capsule endoscopy was performed and revealed a sub-stenosing, vegetating, and bleeding lesion in the first jejunal loop. He underwent laparotomic surgery with resection of the involved segment with loco-regional lymphadenectomy. The pathological report described a poorly differentiated adenocarcinoma of the jejunum, stage IIIA (pT3pN1). Analysis of next-generation sequencing (NGS) of DNA on the surgical sample revealed a likely pathogenetic variant in exon 15 of the DDR2 gene (c.2003G > A) and a TP53 non-frame-shift deletion (c.585_602del). Considering the risk of recurrence, he was candidate to 6 months of adjuvant chemotherapy with platinum salt and fluoropyrimidine. Thirty-eight months after the diagnosis, the patient is still disease free and in good clinical condition. This is the first described case of SBA with DDR2 mutation. Considering the limited therapeutic options beyond surgery for SBA, molecular analyses could become promising for the search for potential targetable alterations for treatments with new available drugs.

Poorly cohesive carcinoma (PCC) is an uncommon neoplasm characterized by tumorous cells exhibiting a lack of adhesion. PCC has been reported rarely in the small intestine other than at the ampulla of Vater. We present a 40-year-old man with recurrent abdominal pain and small bowel obstruction. Imaging revealed an abnormal appearing distal small bowel, with only nonspecific mucosal changes discovered on antegrade and retrograde enteroscopy. On subsequent diagnostic laparoscopy, an ileal mass was found and resected with histopathology showing PCC with signet ring formation. This is an aggressive cancer with a worse prognosis than other small bowel adenocarcinomas.

Adenocarcinoma, while constituting the predominant variant among small bowel cancers, is a component of the broader category of primary small bowel malignancies, which are notably infrequent in occurrence. The diagnosis of such malignancies is often markedly delayed, a consequence of their insidious onset and the nonspecific nature of the abdominal symptoms presented. A 69-year-old Caucasian male presented to the emergency department manifesting acute, sharp, and colicky abdominal pain accompanied by a single episode of vomiting, all developing over one day. His medical history was notable for gastroesophageal reflux disease (GERD) and regionally confined prostate adenocarcinoma, which was under meticulous surveillance by the urological team. The patient\'s lifestyle was characterized by abstention from alcohol and tobacco, adherence to a nutritious diet, and a commitment to regular physical activity. Subsequent examination and surgical excision of an abnormal mass, as delineated on computed tomography (CT), culminated in the diagnosis of a stage IV, poorly differentiated adenocarcinoma. We have reported this case to spark research regarding early diagnostic techniques for small bowel adenocarcinoma (SBA). In this case, a healthy individual presented with vague abdominal pain and a single episode of vomiting. Diagnosis required the surgical resection of the tumor, where metastasis was also visualized. Due to the rare nature of SBA, we believe different diagnostic measures and adjuvant therapy should be researched for earlier diagnosis and subsequently better patient outcomes.

Small bowel adenocarcinoma (SBA) is a rare tumor with a poor prognosis. Due to its rarity, the research infrastructure for SBA, including cell lines, is inadequate. The present study established a novel SBA cell line, SiCry-15X, using patient-derived xenografts of SBA. The following criteria were defined for establishment: Long-term culturability, tumorigenicity and similarity with the original tumor. The biological characteristics of the cell line, its sensitivity to anticancer drugs and its ability to produce tumor markers carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) were evaluated. SiCry-15X cells adhered and grew as a monolayer, with a population doubling time of 37 h. Polymerase chain reaction results confirmed the human origin of the cell line, and short tandem repeat analysis revealed that the cells were genetically identical to the original tumor. The 50% inhibitory concentrations of 5-fluorouracil, paclitaxel, irinotecan, oxaliplatin and cisplatin for SiCry-15X were 104.05, 0.24, 63.3, 146.55 and 49.29 µM, respectively. CEA and CA19-9 concentrations in the culture media were markedly elevated. In addition, CEA and CA19-9 levels in the serum of cell-derived xenograft model mice were elevated. Moreover, CEA and CA19-9 were produced by SiCry-15X cells and distributed throughout the blood. Furthermore, increases in serum CEA and CA19-9 of cell-derived xenograft model mice were consistent with the clinical course of the disease. The newly established SBA cell line, SiCry-15X, could be an effective tool for conducting further studies on SBA.

BACKGROUND: Small bowel adenocarcinoma (SBA) is a rare gastrointestinal malignancy forwhich survival is hampered by late diagnosis, complex responses to treatment, and poor prognosis. Accurate prognostic tools are crucial for optimizing treatment strategies and improving patient outcomes. This study aimed to develop and validate a nomogram based on the Surveillance, Epidemiology, and End Results (SEER) database to predict cancer-specific survival (CSS) in patients with SBA and compare it to traditional American Joint Committee on Cancer (AJCC) staging.
METHODS: We analyzed data from 2,064 patients diagnosed with SBA between 2010 and 2020 from the SEER database. Patients were randomly assigned to training and validation cohorts (7:3 ratio). Kaplan‒Meier survival analysis, Cox multivariate regression, and nomograms were constructed for analysis of 3-year and 5-year CSS. The performance of the nomograms was evaluated using Harrell\'s concordance index (C-index), the area under the receiver operating characteristic (ROC) curve, calibration curves, decision curve analysis (DCA), net reclassification improvement (NRI), and integrated discrimination improvement (IDI).
RESULTS: Multivariate Cox regression identified sex, age at diagnosis, marital status, tumor site, pathological grade, T stage, N stage, M stage, surgery, retrieval of regional lymph nodes (RORLN), and chemotherapy as independent covariates associated with CSS. In both the training and validation cohorts, the developed nomograms demonstrated superior performance to that of the AJCC staging system, with C-indices of 0.764 and 0.759, respectively. The area under the curve (AUC) values obtained by ROC analysis for 3-year and 5-year CSS prediction significantly surpassed those of the AJCC model. The nomograms were validated using calibration and decision curves, confirming their clinical utility and superior predictive accuracy. The NRI and IDI indicated the enhanced predictive capability of the nomogram model.
CONCLUSIONS: The SEER-based nomogram offers a significantly superior ability to predict CSS in SBA patients, supporting its potential application in clinical decision-making and personalized approaches to managing SBA to improve survival outcomes.

In this editorial we comment on the article published \"Clinical significance of programmed cell death-ligand expression in small bowel adenocarcinoma is determined by the tumor microenvironment\". Small bowel adenocarcinoma (SBA) is a rare gastrointestinal neoplasm and despite the small intestine\'s significant surface area, SBA accounts for less than 3% of such tumors. Early detection is challenging and the reason arises from its asymptomatic nature, often leading to late-stage discovery and poor prognosis. Treatment involves platinum-based chemotherapy with a 5-fluorouracil combination, but the lack of effective chemotherapy contributes to a generally poor prognosis. SBAs are linked to genetic disorders and risk factors, including chronic inflammatory conditions. The unique characteristics of the small bowel, such as rapid cell renewal and an active immune system, contributes to the rarity of these tumors as well as the high intratumoral infiltration of immune cells is associated with a favorable prognosis. Programmed cell death-ligand 1 (PD-L1) expression varies across different cancers, with potential discrepancies in its prognostic value. Microsatellite instability (MSI) in SBA is associated with a high tumor mutational burden, affecting the prognosis and response to immunotherapy. The presence of PD-L1 and programmed cell death 1, along with tumor-infiltrating lymphocytes, plays a crucial role in the complex microenvironment of SBA and contributes to a more favorable prognosis, especially in the context of high MSI tumors. Stromal tumor-infiltrating lymphocytes are identified as independent prognostic indicators and the association between MSI status and a favorable prognosis, emphasizes the importance of evaluating the immune status of tumors for treatment decisions.

OBJECTIVE: Small bowel adenocarcinoma (SBA) is a rare malignancy of the gastrointestinal tract, and its unique location within the small intestine presents difficulties in obtaining tissue samples from the lesions. This limitation hinders the research and development of effective clinical treatment methods. Circulating tumor DNA (ctDNA) analysis holds promise as an alternative approach for investigating SBA and guiding treatment decisions, thereby improving the prognosis of SBA.
METHODS: Between January 2017 and August 2021, a total of 336 tissue or plasma samples were obtained and the corresponding mutation status in tissue or blood was evaluated with NGS.
CONCLUSIONS: The study found that in SBA tissues, the most commonly alternated genes were TP53, KRAS, and APC, and the most frequently affected pathways were RTK-RAS-MAPK, TP53, and WNT. Notably, the RTK-RAS-MAPK pathway was identified as a potential biomarker that could be targeted for treatment. Then, we validated the gene mutation profiling of ctDNA extracted from SBA patients exhibited the same characteristics as tissue samples for the first time. Subsequently, we applied ctDNA analysis on a terminal-stage patient who had shown no response to previous chemotherapy. After detecting alterations in the RTK-RAS-MAPK pathway in the ctDNA, the patient was treated with MEK + EGFR inhibitors and achieved a tumor shrinkage rate of 76.33%. Our study utilized the largest Chinese SBA cohort to uncover the molecular characteristics of this disease, which might facilitate clinical decision making for SBA patients.

UNASSIGNED: Small bowel carcinoma (SBC) is a rare malignancy comprising mainly of adenocarcinoma and carcinoid tumors. Among SBCs, small bowel adenocarcinoma (SBA) accounts for 30-40 % and is predominantly found in the duodenum, while jejunal and ileal presence considered rare.
METHODS: We have presented a case of jejunal adenocarcinoma in a patient with obstruction symptoms. Prior to the obstruction, the patient mainly suffered from weakness and weight loss, in addition to iron deficiency anemia. During the investigation of underlying causes, we observed evidence of mass. However, before any additional evaluation could take place, the obstruction necessitated surgical intervention.
UNASSIGNED: Small bowel adenocarcinomas, particularly in the jejunum and ileum, are exceedingly rare and often present with complications such as obstruction, gastrointestinal bleeding, or perforation. Due to the non-specific symptoms, SBAs are challenging to diagnose before complications occur. SBAs are frequently diagnosed at advanced stages, so early diagnosis is crucial, as it can significantly impact patient survival. Thus, efforts should be made to expedite the diagnosis process to avoid complications and improve survival rates.
CONCLUSIONS: SBAs are a rare condition, often diagnosed by related complications. Recognizing the importance of early diagnosis and its positive influence on patient survival, physicians and surgeons should consider SBA in patients presenting with relevant symptoms or cases of obstruction.