Also, it depends upon the origin and type of cancer. Solid tumours usually aren't the cause, unless one classes those of bone marrow as solid, and of lymphoid tissue. But cancer of either of the latter can result in vastly altered WBC counts, in leukaemias, so not impossible he's had a cancer of leukaemic origin which has metastasized. There are actually considerable regions of lymphoid tissue present in the intestines, such as Peyer's patches.
And many lymphoid cells which lie within the ileum, and survey for pathogens for presentation to the ummune system. His WBC count could be elevated as mentioned, if it's a metastatic leukaemia, especially in the case of massive elevation of WBC count. Although severe infection could be a cause, especially given the intestinal necrosis, and the sort of 'stuff' usually found in intestines, is pretty much a blob of microrganisms and coagulated food remains post-processing. Did they say what his CRP levels were like? because his C-reactive protein levels would be elevated in infection during an acute-phase response. And levels of complement types?
I can look up normal values in moments if you'd like any data of that kind, white cell counts (subtypes included), in the oxford handbook of clinical immunology made for doctors and specialists; as I've a copy myself, 'courtesy' I believe, of The Bitch, as It is forever known in this household for evermore, when referring to the borderline PD perditionslut from Tartarus; who was a real light-fingered twat with more purchases on her five finger discount card than anyone else I've ever known. Almost certainly nicked it from some doctor or hospital the moment she saw it. Who, I'll never know, where, likewise. No marks of ownership, so it's remained mine ever since. Quite the interesting reading too.