2024 Volume 39 Issue 3 Pages 306-311
A 70－year－old male presented to our hospital complained of an 80 × 80 mm sized tumor on his buttock, which appeared six years prior to admission. Tumor biopsy revealed a sebaceous adenocarcinoma. Computed tomography revealed enlargement of the right inguinal lymph node (LN), external iliac LN, and obturator LN. We performed radical resection of the primary tumor and NL dissection. Six months after the surgery, the tumor relapsed in the obturator LN. A commercial comprehensive genome profiling test using primary tumor tissue detected high microsatellite instability (MSI－High) and MSH2 nonsense mutations, and pembrolizumab was recommended. After three doses of pembrolizumab, the patient showed a partial response with a reduction in the obturator LN. Even in cases of sporadic sebaceous adenocarcinoma with no past or family history so as to consider the possibility of Muir－Torre syndrome, proactive application for a comprehensive genome profiling test is recommended because MSI－High cases, in which anti－PD－1 antibody is very effective, are included.[Skin Cancer (Japan) 2024 ; 39 : 306－311]
