The Mostly Benign
The Know-It-All Who Knows Nothing: this person is the instant expert on your condition, despite not actually knowing anything about it. Easily identified by their blanket statements and complete inability to do any medical research, they will gladly tell you how "natural foods will cure any cancer" or "you should try *insert current medical fad here*". Most of their medical knowledge will be gleaned from Facebook. Assess their intentions (most of them are actually trying to help) and if you need to use to magic words, "thanks, I will totally look into that".
The Misinformed Overgeneralizer - this person heard "cancer" and has no clue that not only are there many, many different types of cancer but also that the treatments are highly specialized and not universal. Usually their first comment is along the lines of "omg are you gonna lose your hair?" Generally considered benign, they are sometimes worth educating or at least worth throwing a few search terms to set them on the right path.
The Person Who Can't Use Google - sometimes a variant of the Misinformed Overgeneralizer, they are willing to admit their ignorance. However, they will expect *you* to explain everything to them. This person's opinion automatically does not matter, and depending on how much you give a shit about them you can spend the time to explain or you can tell them to Google it for themselves.
The Math-Impaired - this person doesn't understand odds, survival rates, or any statistics whatsoever. Prone to coming to the wrong conclusion or falling for spurious medical studies (they don't understand the concept of sample size at all) they will come to an understanding of the situation that's either overly pessimistic or overly optimistic. Best ignored.
The Story Teller - this person is usually suffering from the need to say something but not knowing what to say. They will typically try to find common ground, and will sometimes succeed if they're a survivor or close to a survivor. However most of the time they will fall flat on their faces. The stories will run from reasonable attempt ("my aunt had a cancer kind of like that and she survived") to the distressing ("my brother just died from _____ cancer, it was horrible") to the utterly insulting ("my dog had prostate cancer so I totally know what you're going through.") Generally these people are at least trying to do the right thing, so you can at least smile and nod.
The Stunned and Wordless - self-explanatory. These people will mumble "I'm so sorry" when they get their wits back. They're benign, they just have no clue what to do.
The Road to Hell is Paved with These Guys
The Fixer - diet, juice cleanse, exercise, meditation, hypnotherapy, acupuncture - this person puts their trust in everything other than modern Western medicine. They will argue with you over the best treatment for their condition while (unironically, somehow) telling you that surgery, radiation, and chemotherapy will kill you. Sometimes they're right in that some people die from the treatments but they completely ignore the very important fact that an untreated malignant cancer will generally kill you much faster.
The Fixer, Religious Variant - pray enough and it will go away, have enough faith and God will heal you. You will somehow resist the urge to tell them that yes, God has answered your prayers and He will heal you... with the help of your cancer treatment team.
The Fixer, Cannabis Variant - do I really need to explain this one?
The Saint-Makers and Pedestal Builders - yes, they intend it as a compliment when they say "bless you, I could never manage keep calm and carry on in your circumstances". They honestly don't understand that it's really lonely up on that pedestal, and that you don't really want to feel superhuman at the moment, and that you really, REALLY don't want to think of your situation as that bad and unmanageable. These guys will take the wind out of your sails without knowing it, so do your best to accept it as a compliment and remember that if they were in your position they'd probably buck up and manage too.
The More Distressed Than Thou - this person is not close to the patient or otherwise impacted by the cancer but somehow has FOUND A WAY to be more upset over the news than you are. There may be hysterics, sobbing, rending of garments or other displays of extreme emotion and those displays will be calculated to get the most attention possible. Sometimes they will suck you into comforting *them*. Avoid them at all costs.
The Conspiracy Theorist - an odd mix of the Blamer and the Fixer, this person should be benign. They're not. In all of their ranting about how Monsanto gave you the cancer and Big Pharma is hiding the universal cancer cure in a bid to get more money, they are actually demonstrating their ability to not be sheeple and not be brainwashed. Congratulations, you are now a character in their latest narrative about how The Man is killing us all.
The Nihilist - "If I were you I'd just kill myself and get it over with." Gee, thanks for that vote of confidence! This person will sap your will to live as they prove to themselves that life isn't worth living.
The Fault-Finder - this person invariably is an adherent to *some* sort of religion or dogma and needs to find the reason that you, personally, are going through cancer, Their reason is usually a variation of their concept of sin. God is smiting you personally for your sins, you smoked or did drugs, you're not a vegan, you're not eating organic, any reason will do. As long as they can come up with some reason why you're sick that's your fault they can avoid the uncomfortable truth that cancer could happen to them, too.
The Doers and the Helpers
The Truly Empathetic - this person will listen to you rant, give you a shoulder to cry on, and otherwise be a support as best they can.
The Helper - like the Truly Empathetic they want to help you, but may not know what to say. Instead they'll show up and clean your house, bring you meals, visit you at the hospital, watch your kids, do your laundry, and otherwise help you with keeping life together.
The Avenger - this person lost someone to cancer and WILL NOT LET CANCER WIN AGAIN DAMNIT. Will do as much as they can to help you have a positive outcome, including all sorts of medical, mental, emotional, physical, and logistical support.
The Survivor - like the Truly Empathetic and the Helper they can be an invaluable resource and support, but unlike the Truly Empathetic or the Helper their knowledge of how to get through comes from real experience, either their own or from going through cancer with someone really close to them. They are the Tribe you will become part of for the rest of your life.