Colon cancer (CC) is one of the most commonly diagnosed tumours worldwide. Single‐cell RNA sequencing (scRNA‐seq) can accurately reflect the heterogeneity within and between tumour cells and identify important genes associated with cancer development and growth. In this study, scRNA‐seq was used to identify reliable prognostic biomarkers in CC. ScRNA‐seq data of CC before and after 5‐fluorouracil treatment were first downloaded from the Gene Expression Omnibus database. The data were pre‐processed, and dimensionality reduction was performed using principal component analysis and t‐distributed stochastic neighbour embedding algorithms. Additionally, the transcriptome data, somatic variant data, and clinical reports of patients with CC were obtained from The Cancer Genome Atlas database. Seven key genes were identified using Cox regression analysis and the least absolute shrinkage and selection operator method to establish signatures associated with CC prognoses. The identified signatures were validated on independent datasets, and somatic mutations and potential oncogenic pathways were further explored. Based on these features, gene signatures, and other clinical variables, a more effective predictive model nomogram for patients with CC was constructed, and a decision curve analysis was performed to assess the utility of the nomogram. A prognostic signature consisting of seven prognostic‐related genes, including CAV2 , EREG , NGFRAP1 , WBSCR22 , SPINT2 , CCDC28A , and BCL10 , was constructed and validated. The proficiency and credibility of the signature were verified in both internal and external datasets, and the results showed that the seven‐gene signature could effectively predict the prognosis of patients with CC under various clinical conditions. A nomogram was then constructed based on features such as the RiskScore, patients' age, neoplasm stage, and tumor (T), nodes (N), and metastases (M) classification, and the nomogram had good clinical utility. Higher RiskScores were associated with a higher tumour mutational burden, which was confirmed to be a prognostic risk factor. Gene set enrichment analysis showed that high‐score groups were enriched in ‘cytoplasmic DNA sensing’, ‘Extracellular matrix receptor interactions’, and ‘focal adhesion’, and low‐score groups were enriched in ‘natural killer cell‐mediated cytotoxicity’, and ‘T‐cell receptor signalling pathways’, among other pathways. A robust seven‐gene marker for CC was identified based on scRNA‐seq data and was validated in multiple independent cohort studies. These findings provide a new potential marker to predict the prognosis of patients with CC.

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Background： Neuroendocrine carcinoma mainly occurs in the lung and gastrointestinal tract, rarely in the urinary tract. The proportion of neuroendocrine carcinomas was less than 0.05 % [2] in urinary malignant tumors. The most common location of neuroendocrine carcinomas in the urinary system is the bladder. Fewer neuroendocrine carcinomas occur in the ureter than in the bladder. Case presentation: A 62 years old woman presented with right ureteral obstruction due to ureteral mass. The patient began chemotherapy 2 weeks after surgery. During the 14-month follow-up, the patient received 6 courses of etoposide and Carbopol chemotherapy, and imaging examination showed no signs of recurrence. Postoperative pathological examination showed large cell neuroendocrine carcinoma of the right ureter. Conclusions: Large cell carcinoma of ureter has a rapid course of disease and poor prognosis. Ureteral large cell carcinoma is a very rare tumor. At present, there is no specific treatment scheme. However, considering the good response of its lung counterpart to the standard chemotherapy scheme and the experience of the cure of related urinary large cell carcinoma by chemotherapy [28], we argue that platinum-based chemotherapy is effective for it and patients can benefit from it. The multimodal treatment scheme of surgery combined with platinum-based chemotherapy is the current standard scheme for the treatment of ureteral neuroendocrine carcinoma.

Background：Neuroendocrine carcinoma mainly occurs in the lung and gastrointestinal tract, rarely in the urinary tract. The proportion of neuroendocrine carcinomas was less than 0.05 % [2] in urinary malignant tumors. The most common location of neuroendocrine carcinomas in the urinary system is the bladder. Fewer neuroendocrine carcinomas occur in the ureter than in the bladder. Case presentation: A 62 years old woman presented with right ureteral obstruction due to ureteral mass. The patient began chemotherapy 2 weeks after surgery. During the 14-month follow-up, the patient received 6 courses of etoposide and Carbopol chemotherapy, and imaging examination showed no signs of recurrence. Postoperative pathological examination showed large cell neuroendocrine carcinoma of the right ureter. Conclusions: Large cell carcinoma of ureter has a rapid course of disease and poor prognosis. Ureteral large cell carcinoma is a very rare tumor. At present, there is no specific treatment scheme. However, considering the good response of its lung counterpart to the standard chemotherapy scheme and the experience of the cure of related urinary large cell carcinoma by chemotherapy [28], we argue that platinum-based chemotherapy is effective for it and patients can benefit from it. The multimodal treatment scheme of surgery combined with platinum-based chemotherapy is the current standard scheme for the treatment of ureteral neuroendocrine carcinoma.