Acral metastasis of colonic cancer: A case report

Background: Colorectal cancer (CRC) is the third most common malignancy worldwide and accounts for 9.4% of all cancer-related deaths, making it the second leading cause of cancer mortality. Approximately 70% of patients develop metastatic disease, most commonly to the liver and lungs. Acral metastasis, particularly to the digits, is extremely rare and usually indicates advanced disease with a poor prognosis.

Case presentation: We report a rare case of digital acrometastasis from colorectal adenocarcinoma in a 55-year-old male. The patient presented with a painful lesion on his right index finger, characterized by discoloration, a wound cavity, and granulation tissue at the fingertip. The patient had a prior history of treated colon cancer and was receiving immunotherapy. He underwent wedge excision and nail avulsion of the affected finger. Histopathological examination confirmed metastatic adenocarcinoma with an immunohistochemical profile consistent with colorectal origin. The patient was referred to the National Center for Cancer Care and Research (NCCCR); however, no follow-up information was available, as he did not return for further evaluation.

Discussion: Bone metastasis from CRC is uncommon, and acrometastasis to the digits occurs in only 0.007–0.2% of cases. The differential diagnosis of digital lesions can be challenging and should include both benign and malignant conditions. Immunohistochemical staining is crucial for diagnosis, and with metastatic CRC typically expressing cytokeratin 20 (CK20) and caudal type homeobox (CDX2), it helps distinguish it from primary digital adenocarcinomas. Clinicians should consider acrometastasis in patients with a history of CRC who present with unexplained digital lesions.

Conclusion: This case underscores the rare potential of CRC to metastasize to acral regions, including the distal phalanges. Clinicians should maintain a high index of suspicion for metastatic disease when evaluating digital lesions in patients with a history of malignancy, as timely diagnosis and management are essential for optimizing patient outcomes.