Penile metastasis from a duodenal gastrointestinal stromal tumor: A rare case report.

Penile metastases are rare, and metastasis of a gastrointestinal stromal tumor (GIST) to the penis is exceedingly uncommon. An 81-year-old man with a history of duodenal GIST, initially treated with curative resection and tyrosine kinase inhibitor therapy for liver metastasis, presented with an enlarging penile mass. A biopsy confirmed penile metastasis from GIST. To relieve his symptoms, a total penectomy was performed. Molecular testing revealed a KIT exon 9 mutation and CDKN2A/B gene alterations, indicating aggressive tumor behavior and resistance to standard treatment. This case underscores the importance of recognizing atypical metastatic sites in GIST.