Colorectal Cancer Developing From Residual Colorectal Mucosa at a Previous Temporary Colostomy Site: A Case Report and Literature Review

Colorectal cancer (CRC) is one of the most common cancers [1]. However, its development at colostomy sites is considered extremely rare because of the limited exposure to intestinal bacteria and stool [2]. Herein, we present the first case of CRC originating from the residual colorectal mucosa in the abdominal skin after colostomy closure. A 66-year-old Japanese man presented with a 5-year history of a gradually enlarging mass in his left lower abdomen. He had a history of a temporary sigmoid colostomy at the same site following a rectal perforation caused by a traffic accident 36 years prior, with colostomy closure performed the following year. Two weeks prior to his visit, he was admitted to the emergency department with left lower abdominal pain. A biopsy performed at a previous hospital suggested skin metastasis of CRC. However, the patient had no history of any malignancy, including CRC. Physical examination revealed a 17 × 15 cm pale-red mass with an irregular surface and ulceration in the left lower abdomen (Figure 1a). Contrast-enhanced computed tomography (CT) revealed a mass adjacent to the muscle layer, meaning possible muscle invasion could not be excluded (Figure 1b). Fluorodeoxyglucose (FDG)-positron emission tomography-CT showed no FDG accumulation suggesting a primary lesion or metastasis in any organs or lymph nodes other than the tumor. Upper and lower endoscopies showed no tumorous lesions. The tumor was excised with a 2 cm surgical margin that included the rectus abdominis muscle and part of the peritoneum (Figure 1c,d). Histopathological examination revealed the proliferation of irregularly shaped lumina extending from the dermis into the subcutaneous tissue (Figure 1e,f). These were lined with atypical cells exhibiting partial mucinous changes (Figure 1h,i). A transition from the epidermis to the mucosal epithelium was observed at the tumor margin (Figure 1g). Immunohistochemical staining showed that the tumor cells were positive for cytokeratin (CK) 20 (Figure 1j) and caudal-type homeobox 2 (CDX2; Figure 1k), but negative for CK7 (Figure 1l). Based on these findings, the patient ultimately was diagnosed with CRC originating from the residual mucosa at the colostomy closure site. No recurrence has been observed for 18 months following the excision. We reviewed 48 published cases of CRC arising at colostomy sites (Table S1) [3, 4]. The male-to-female ratio was 1.2:1, and the mean onset age was 68.5 years. Most cases had prior histories of CRC (Figure S1a). The average duration from colostomy to cancer diagnosis was 19 years (range: 1–42). The mean tumor size at diagnosis was 5.9 cm, making our case the largest reported (17 cm). These CRCs may have larger tumor sizes because of delayed detection. All previous cases with available treatment details underwent surgical resection, with the estimated 5-year overall survival rate, via the Kaplan–Meier method being 71.9% (Figure S1b). The mechanism of onset remains unclear; however, given the absence of exposure to bacteria and stool, this CRC may represent de novo malignant transformation arising from residual colorectal mucosa. Long-term surveillance should be maintained for neoplastic changes at colostomy scars, even decades after closure. The authors declare no conflicts of interest. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions. Figure S1: (a) Summary of the comorbidities of 48 previously reported cases of colorectal cancer (CRC) arising at colostomy sites. Table S1: Forty-eight previously reported cases of carcinomas arising at colostomy sites. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.