Cancers grow, uncontrollably. It's kind of their definition. This inexorable genesis has side effects.
Perhaps the most curious one, to my mind, is death.
Folks develop a cancer that grows, generating a tumour, a lump, a mass. This often isn't enormous. Our bodies cope with lumps pretty well. People have parasites forming walled off spheres inside us (like hydatid disease). People have inflammatory process generating fluid filled cysts inside us. People have infections generating cavitating lesions or pus filled tissues inside us. Heck, people have babies, with the extra mass of fluid and placenta and baby.
Our bodies can cope with extra lumps inside us, so having a cancer the size of an apple or grapefruit isn't understandable as a cause of death. Sure, if it eats through something important, like an artery, and you bleed to death, that's evidently a clear cause of death. But most people with cancer thankfully don't pass away so dramatically, bleeding catastophically. So why's a lump, just sitting inside you, being a lump, fatal?
One of the common consequences of cancer I see is the paraneoplastic syndrome. This is when cancer causes problems through growing, endlessly, but instead of the mass causing direct symptoms the growth throws out gunge. The tumour churns out lots of chemicals. Hormones and the like. Or things that drive the body to do something/stop doing something. This explains why a tumour causes lots of symptoms (and accounts for why just having a lump that's hardly pushing on anything doesn't directly cause symptoms).
Unfortunately many effects of this can be pretty common. Tiredness. Weight loss. Temperature. Joint pain. Nausea. Mood changes. Confusion.
The last couple months have resulted in several patients being referred to me with ?dementia and history, examination and investigation's found a previously unknown adenocarcinoma causing their presenting symptoms. None had cerebral metastases. None had neurodegenerative dementia. Their symptom burden was part of the neuropsychiatric sequelae of cancer.
The cancer is active, endlessly growing and making and actively synthesising, with the unhappy byproduct of churning out a lot of gunge which makes people feel hellishly unwell. And I can't fix that.