A 58-year-old postmenopausal woman presents to the clinic with a 3-month history of a gradually enlarging, firm nodule at her umbilicus. She reports mild abdominal discomfort and unintentional weight loss of 10 kilograms over the past six months. The nodule has become tender over the last few weeks, and she has noticed occasional serosanguinous discharge. She denies nausea, vomiting, or changes in bowel or urinary habits. Her medical history is unremarkable, and she has no significant family history of cancer. On physical examination, there is a 2 cm firm, irregular, non-reducible nodule at the umbilicus with overlying erythema and a small amount of discharge. Abdominal palpation reveals mild diffuse tenderness but no palpable masses. No ascites is detected on percussion. The presence of a nodule at her umbilicus made you wonder whether this is a Sister Mary Joseph nodule. Which of the following malignancies is most commonly associated with Sister Mary Joseph nodules?
