Case Report: BRCA1 and BRCA2 loss in a young man with primary cutaneous extraskeletal osteosarcoma

Primary cutaneous extraskeletal osteosarcoma (PC-EOS) is rare, and preoperative differential diagnosis is difficult. This is the first report of PC-EOS with decreased copy number of <i>BRCA1</i> and <i>BRCA2</i>. The presented case highlights the importance of accurate histopathological examination and comprehensive analysis. We considered that <i>BRCA1</i> and <i>BRCA2</i> genes may are associated with a worse outcome and local recurrence in PC-EOS. But, it may not have been fully recognized.