What does it mean when a stomach tumor has blood and pus excreting from it?

Dead tissue: Tumors that are bleeding and infected may be so large that they have outgrown their blood supply, and are partially necrotic (dead), and that portion of the tumor is essentially food for bacteria. Obviously, there are many other scenarios, so hard to tell if this is answers your question, but i hope it helps.

Malignant tumor: Nodular lesions of the stomach such as GIST or LeiomyoSa rarely have active bleeding. The latter occurs from ulcerating malignancies especially prepyloric or along gastric curvature. Such lesions that do not heal on meds require resection since they invade blood vessels to bleed and frequently have helicobacter pylori which can induce the infection with pus formation.