Pathological Complete Response and Conversion Gastrectomy after Nivolumab Plus FOLFOX in an 84-Year-Old Man with MSI-High Gastric Cancer Presenting as a Sister Mary Joseph Nodule: A Case Report.

A Sister Mary Joseph nodule is a cutaneous umbilical metastasis indicating advanced intra-abdominal malignancy with a poor prognosis. An 84-year-old man presented with an umbilical nodule that was completely excised and diagnosed to be metastatic adenocarcinoma from advanced gastric cancer. After FOLFOX-nivolumab, the primary lesion and lymphadenopathy showed near-complete radiographic regression, and conversion total gastrectomy achieved a pathological complete response. The indications for surgery were insufficient, and therefore systemic therapy or surveillance was continued. This case highlights the uncertainty surrounding conversion surgery after an immune checkpoint inhibitor-induced near-complete response and suggests that neither umbilical metastasis nor advanced age alone should preclude the consideration of curative-intent multimodal treatment in fit patients.