Penile metastasis from colon cancer with BRAF V600E mutation treated with BRAF/MEK-targeted therapy plus cetuximab: A case report.

Background: The incidence of colon cancer has been progressively increasing over time, whereas penile metastasis of colon cancer has remained exceedingly uncommon. Since the prognosis for colon cancer with BRAF ^V600E mutation is relatively unfavorable, further exploration and investigation are still required to develop treatment strategies for such rare cases.

Case summary: About one year after surgery and chemotherapy, a 50-year-old patient with sigmoid colon cancer developed a mass at the base of the patient's penis, accompanied by severe tenderness and pain during urination. With disease progression, multiple metastatic nodules also emerged in other regions of the penis, including the coronal sulcus. The nodules located in the coronal sulcus were excised for histopathological examination. The histopathological findings revealed that the nodules were metastases originating from the sigmoid colon cancer, with a BRAF ^V600E mutation detected. This prompted a modification of the therapy regimen of cetuximab, dabrafenib and trametinib, which effectively held back the progression of penile metastasis in the patient.

Conclusion: Combining the BRAF/MEK-targeted therapy with cetuximab demonstrates a favorable therapeutic response in BRAF ^V600E-mutated colon cancer with penile metastasis.