Extramammary Paget's disease (EMPD) is a rare cancer that occurs within the epithelium of the skin, arising predominantly in areas with high apocrine gland concentration such as the vulva, scrotum, pe Show more
Extramammary Paget's disease (EMPD) is a rare cancer that occurs within the epithelium of the skin, arising predominantly in areas with high apocrine gland concentration such as the vulva, scrotum, penis and perianal regions. Here, we aim to integrate clinicopathological data with genomic analysis of aggressive, rapidly-progressing de novo metastatic EMPD responding to HER2-directed treatment in combination with other agents, to attain a more comprehensive understanding of the disease landscape. Immunohistochemical staining on the scrotal wall tumor and bone marrow metastasis demonstrated HER2 overexpression. Whole genome sequencing of the tumor and matched blood was performed. Notable copy number gains (log Whole genome sequencing revealed the underlying copy number variation landscape in HER2-positive metastatic EMPD. The presence of alternative signalling pathways and genetic variants suggests potential interactions with HER2 signalling, which possibly contributed to the HER2 overexpression and observed response to HER2-directed therapy combined with other agents in a comprehensive treatment regimen. Show less