As an oncologist, I have spent my career learning how to break bad news. I am still not entirely sure how to tell my children about the tumor in my pancreas, why I will be gone from our home next week for a Whipple operation, or my excuse for abstaining from wrestling matches for the foreseeable future.

I am blessed with two kids, temperamentally diametric: a careful, sagacious nine-year-old daughter and an impetuous, free-spirited six-year-old son. Tragically he has inherited MEN1 from me, but I suspect this is providential insofar as his demeanor is better suited to a lifetime spent engaging the health care system in tumor surveillance. He finds the human body fascinating — the grosser, the better — and has already chased his sister around our house with pictures from a recent endoscopy. He loves my guts.

He was not always so bold. On his first visits to the beach, he was tentative to enter the water. This was an uncharacteristic caution for him. He was a boisterous child with blatant disregard for gravity, willing to fall to fly. Once bitten, never shy, thin, white lines propagated on his skin like rings in a tree: a new year, a new scar.

I told him not to be afraid, that the water was very shallow and that I would walk with him into the waves. Still, he refused. When I asked him why he wouldn’t go in he replied, “The naughty crabby will pinch me.” I had to convince him not to be afraid of the crab.

It’s so tempting to liken cancer to a ravenous animal, but it’s worse than that. It’s not even a parasite, trying to occupy one host and move on to the next one, forever restless and nomadic. It cares only about its own replication, and it never wants to leave. It suppresses your appetite even as it steals your calories, unaware that you are not a renewable resource, plundering your energy until there’s nothing left to catabolize. Its duty is to completely drain you.

The crab sometimes seems like the wrong representative for cancer. I understand how the association was made, between the clacking claws and the probing appendages of a tumor hungry for incursion on neighboring tissues. The thick carapace, tough to penetrate, also makes a suitable symbol for resistance. Once, during an autopsy of a patient I lost to pancreatic adenocarcinoma, I reached into the depths of their abdomen and felt the tumor; that malignancy in particular tries to encase itself in hyaluronan, and indeed, to my probing fingers, it felt like concrete had been poured into the cavity. I know this sounds like a ghastly laying on of hands. But posthumously, I could make sense of why my chemo had found its target impenetrable. Shells are deliberately hard to crack.

But crabs also retreat when you approach. Whatever represents cancer should surely be less skittish, something more feral and deadly. In mythology, the crab bit Hercules on the foot, after which he was able to crush it easily. We dream that this disease could be so easily dispatched.

A reptile seems more appropriate. Ever since year one of med school, I’ve been fascinated that medicine is symbolized by a snake curling around a staff. Perhaps the rod of Asclepius is meant to depict that the serpent has been man’s adversary since Eden, damning us to lives of toil. In myth the snake that encircles the staff is non-venomous but oncologists know the truth: that our bodies can become adversarial through mutation, to the point that only poison can purge them. Spare the rod, spoil the patient.

The scorpion, its tail spring-loaded with sting, works emblematically too, especially in the fable where it strikes the frog ferrying it across the river, sinking to mutual doom. When cancer steals nutrients from its host, a dumb leech, it unknowingly shortens its own lifespan. Here we can circle back to the imagery of the snake, an ouroboros that grows so large it begins eating its tail.

Perhaps I identify most with the serpent and the spider because, like them, venom is my weapon of choice. In Hindu literature, Shiva detoxified the ocean, storing in his throat all the contaminants he siphoned from the salt water. He had three purposes to serve — creation, preservation, destruction — and stockpiled his vitriol to negate that which he had made and no longer wished to maintain. Finding himself in a world already formed and perpetuating itself, man never gets closer to the gods than when he annihilates.

Oppenheimer felt the terrible power he unlocked when he saw the atomic explosion at the Trinity site, mouthing the Bhagavad Gita in awe, “I am become Death, the destroyer of worlds.” Oncologists feel similarly astonished by their ruinous potential when unleashing a chemical counterattack against the primordial nuclear weapons, which mushroom not in clouds but in bodies.

Perhaps the best spirit animal for cancer is the Hydra, which the crab Karkinos picked as an ally in the fight against Hercules. This beast was tailor-made by Hera, wife of Zeus, to slay the strongest of men. For each head severed by the sword, it grew two more. A malignancy co-opts the regenerative capacity of normal cells, but is seldom content with such a modest doubling of itself; charting its toil and trouble requires a logarithmic scale. We aim to blunt its exponential rise with poisons that cry out for antivenin.

Unleashing a flood that drowns the good with the bad has been done before, of course, if we are comparing ourselves to deities in our capacity for liquidation. We hope to keep the patient afloat in an ark as the waves roll in, but their vessel is vulnerable to sabotage by stowaways. Worse than rats they multiply two by two until both ship and hope are sunk.

There, in the storm-roiled deep, we return one last time to the tenacious crustacean as totemic for cancer. After the deluge, we can still find its ragged claws scuttling across the floors of silent seas.

I am writing this partly as a legacy for my son, the youngest in my family to carry the burden of multiple endocrine neoplasia type 1. One day he too might need to undergo a Whipple, although I suspect — hope! — that by then the medical profession will have mastered less invasive ways to tame the pancreas.

Already, though, I have stood with him by the ocean. I have wondered how he will chart the course ahead; negotiate the crests and troughs; endure the tempests and the doldrums.

I hope I have taught him to enjoy the beach in spite of the crab. Naughty as it may be, it does not cancel out life’s beauty: the feeling of sand between your toes, the lunar pull on the water lapping at your feet, the irresistible wonder at what’s beyond the horizon.

Mark A. Lewis is a gastroenterologist who blogs at Of Tumors and M.E.N.  He can be reached on Twitter @marklewismd.

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