Cancer Drug Triggers Eruptive Keratoacanthoma in Patient
A 75-year-old woman taking capecitabine for metastatic colorectal cancer developed dozens of skin lesions that clinicians were warned could be mistaken for squamous cell carcinoma.
Updated on Nov. 3, 2026 in Cancer
A 75-year-old woman with sigmoid colon cancer that had spread to bone developed dozens of rapidly growing skin lesions on her face and neck over two months while taking the oral chemotherapy drug capecitabine. Pathology identified the condition as eruptive keratoacanthoma.
Why it matters
The case highlights that eruptive keratoacanthoma can be misdiagnosed as squamous cell carcinoma, which could lead to inappropriate treatment. Understanding the link between capecitabine and skin lesions helps clinicians recognize the reaction early.
The report describes one 75-year-old patient, with lesions appearing over two months and genetic testing revealing missense mutations in the MTOR gene. It remains unclear how common this reaction is and whether the MTOR mutations contributed to it.
The players
Capecitabine
An oral fluoropyrimidine chemotherapy drug that is converted in the body to 5-fluorouracil.
The details
Capecitabine converts to 5-fluorouracil (5-FU), which inhibits cancer cell growth; 5-FU is itself used to treat keratoacanthoma. The patient had not received immunosuppressive therapy, and the lesions were firm, flesh-colored to reddish nodules, some with small blood-stained crusts.
Timeline
Lesions developed over a period of two months during capecitabine treatment.
Health Landscape
Capecitabine is an oral prodrug that converts to 5-fluorouracil, the same agent used to treat keratoacanthoma. This case adds to reports of cutaneous reactions to fluoropyrimidine chemotherapy that clinicians must distinguish from malignant skin cancers.
Patients taking capecitabine who notice new, rapidly growing skin bumps should report them to their care team so they can be evaluated and not assumed to be a cancer spread. Clinicians can use the 5-FU link to consider this reaction when reviewing skin changes during treatment.
The takeaway
Rapidly appearing skin lesions during cancer treatment deserve careful diagnosis, since a benign-appearing reaction can resemble a more serious cancer. Patients should report new skin changes promptly to their care team.
Further reading
Explore more on Cancer to see how treatment side effects like these are monitored.
Source note: This article includes information reported by Kenya Today.
