原发性结直肠鳞状细胞癌（CSCC）是一种罕见的病理亚型。目前，有关其预后和治疗的临床数据有限，尚无最佳治疗方法。该病例涉及一名熟练错配修复 (pMMR) 和微卫星稳定 (MSS) 结直肠癌 (CRC) 患者，其患有横向位于结肠的鳞状细胞癌 (SCC)。根据影像学评估，肿瘤浸润深度分类为T4。接受4个周期的奥沙利铂联合卡培他滨（XELOX）新辅助治疗后，患者在2个周期中评估部分缓解（PR），在4个周期中评估疾病稳定（SD）。该患者接受了右半结肠切除术，并接受术后紫杉醇/顺铂（TC）辅助化疗。 23个月后，全身检查发现腹部转移。对检测到的腹部转移瘤进行针活检，所得病理结果表明存在转移性鳞状细胞癌。该个体表现出程序性细胞死亡配体 1 (PD-L1) 的表达和 TP53 基因的突变。根据病史考虑患者病情复发，制定治疗方案。这涉及信迪利单抗加西妥昔单抗以及亚叶酸、氟尿嘧啶和伊立替康 (FOLFIRI) 方案的组合。该患者接受了 4 个周期的疗效评估为 SD- 的治疗，以及 7 个周期的疗效评估为 SD 的治疗，无进展生存期 (PFS) 持续时间为 7 个月。本案例研究介绍了传统的 XELOX 化疗方案，该方案的有效性有限，并强调了在诊断为原发性结肠 SCC 的个体中实施 TC 辅助化疗方案所取得的有利结果。此外，将免疫检查点阻断 (ICB) 与其他疗法结合起来治疗晚期疾病患者预计可以延长生存期。版权所有 © 2023 Wu、Su、Wei、Hong 和 Wang。

Primary colorectal squamous cell carcinoma (CSCC) is a rare pathological subtype. Currently, clinical data with regards to its prognosis and treatment is limited, and there is no optimal treatment method. The case presented involves a proficient mismatch repair (pMMR) and microsatellite-stable (MSS) Colorectal cancer (CRC) patient with squamous cell carcinoma (SCC) located transversely in the colon. Based on the imaging assessment, the tumor infiltration depth is classified as T4. After receiving 4 cycles of neoadjuvant treatment with oxaliplatin and capecitabine (XELOX), the patients were evaluated for partial response (PR) in 2 cycles and stable disease (SD) in 4 cycles. The patient underwent a right hemicolectomy and received postoperative paclitaxel/cisplatin (TC) adjuvant chemotherapy. After 23 months, a systemic examination revealed abdominal metastasis. A needle biopsy was conducted on the detected abdominal metastases, with the resulting pathology indicating the presence of metastatic SCC. The individual exhibited expression of programmed cell death ligand 1 (PD-L1) and a mutation in the TP53 gene. Considering the patient's disease recurrence based on medical history, a treatment plan was formulated. This involved Sintilimab plus Cetuximab and the combination of leucovorin, fluorouracil, and irinotecan (FOLFIRI) regimen. The patient received four cycles of treatment with an efficacy evaluation of SD- and seven cycles of treatment with an efficacy evaluation of SD+, which resulted in a progression-free survival (PFS) duration of 7 months. This case study presents the conventional XELOX chemotherapy protocol, which has shown limited effectiveness, and highlights the favorable results achieved by implementing the TC adjuvant chemotherapy regimen in individuals diagnosed with primary colonic SCC. Furthermore, combining immune checkpoint blockade (ICB) with other therapies for patients with advanced disease is anticipated to provide an extended duration of survival.Copyright © 2023 Wu, Su, Wei, Hong and Wang.