Eve Ensler, sharing her experience of illness in the one-woman show “In the Body of the World.” Sara Krulwich/The New York Times

Eve Ensler has a word she wants you to get comfortable with.

No, not that one.

Her remarkably successful play “The Vagina Monologues,” first seen Off Off Broadway in 1996 and then pretty much all over the world except where it was banned, helped normalize the frank discussion of women’s sexuality (and anatomy) onstage. It also fostered and financed a project called V-Day, which has raised tens of millions of dollars for antiviolence organizations.

But the new word Ms. Ensler wants you to embrace — a word that is the subject of her play “In the Body of the World,” which opened on Tuesday in a Manhattan Theater Club production — is not so lovable. It’s “tumor.”

In May 2010, just as she was about to attend the opening of City of Joy, a sanctuary she helped to found for rape victims in Congo, Ms. Ensler received a diagnosis of uterine cancer. “In the Body of the World,” directed by Diane Paulus, is a troubling record of her attempt to survive that illness, in part by understanding its meaning. Had she somehow poisoned herself, as humans every day poison the earth? (The recent BP oil spill in the Gulf of Mexico was on her mind.) Could the disease growing inside her be an expression of the global disease of violence done to women by men?

“Cancer threw me into the center of my body’s crisis,” she says near the beginning of the play. “The Congo threw me into the crisis of the world, and these two experiences merged as I faced what I felt sure was the beginning of the end.”

This is grim stuff, but you will recognize from earlier works Ms. Ensler’s palliative strategies. With her Scarsdale honk and Louise Brooks bob, she still presents herself as your wacky activist bohemian aunt, the kind who tried to “unionize all the unpopular girls” in high school. She bubbles with psychological insight and empathy for anyone in distress.

And, as always, she laces her tales with humor, gallows or otherwise. Rochester, Minn., where she undergoes treatment at the Mayo Clinic, is called Tumor Town; her encounter there with Cindy the “fart deliverer” is destined to be a comic audition piece for decades.

But unlike “The Vagina Monologues” and a later play, “The Good Body,” which were told in the voices of many different women, “In the Body of the World” is all Ms. Ensler all the time. For 80 minutes, she impersonates no one else, except in passing.

The result is a story that’s less about connecting to people than to ideas, some of them fairly airy. Whether the play’s intensely autobiographical self-focus will come off as liberating or oversharing depends, in part, on how open you are to the meanings of those connections. I was often troubled by them.

The production also delves into Ms. Ensler’s encounters with rape victims in Congo. Sara Krulwich/The New York Times

To begin with, Ms. Ensler seems to blame herself (and her icy, narcissistic mother) for her cancer. She has lived much of her life, she says, preoccupied with a feeling of exile from her body and a frantic struggle to return to it through “promiscuity, anorexia, performance art.” Never having given birth, she even wonders if the tumor now growing within her is a “trauma baby.”

But what eventually turned a putative predisposition into the hard fact of cancer, she concludes, is the evil she bore witness to in Africa. In an earlier trip to Congo, she listened as a woman named Angelique told a tale of unimaginable horror. “It was here I walked out of the world,” Ms. Ensler says. “Here in the suspended somnolent zone where I told my body to die.”

One cannot but honor Ms. Ensler’s devotion to facing and improving the world. She has arguably done as much practical good as any playwright now working. And it’s understandable that in telling a story that takes place in her own body an activist would want to connect it to something beyond that small space.

But aside from painting disease as a kind of moral rebuke — an idea that many people with cancer, and their loved ones, will find distasteful — “In the Body of the World” seems to flow in the wrong direction. Rather than using Ms. Ensler’s illness to illuminate the world’s, it too often borrows from the world’s suffering in an effort to legitimize her own.

Suffering at any level doesn’t need legitimizing, and survival is not, in itself, selfish. The story of Ms. Ensler’s disease, which she first related in a 2013 memoir of the same title, would have been compelling enough on its own to justify a play; in that respect, she had me at “tumor.”

As a performer, she seems to know that. Whenever she returns from her spiritual, political and environmental disquisitions to the medical and personal heart of the story, the wet feeling of longing for significance that sometimes swamps the narrative dries right up. And Ms. Ensler is never more trenchant (or self-aware) than when butting against a bureaucracy. After a doctor suggests radiating her vagina to prevent recurrence, she says, in mock dudgeon but with real irony, “Do you have any idea who I am?”

Still, I could do without the tribute to every nurse and friend and assistant who helped her through the ordeal; these namechecks make it sound as if she is giving an acceptance speech at an awards show for winning cancer. Seeing Ms. Ensler so obviously invigorated is happy ending enough.

Until then, Ms. Paulus — who staged the play’s 2016 premiere at the American Repertory Theater — keeps the production spare, with little more than a divan, a chair, some projections (by Finn Ross) and sound effects (by M. L. Dogg and Sam Lerner) to support the monologue. All the more lovely, then, is the scenic coup prepared by the designer Myung Hee Cho, which leaves the audience with a vision of what it can mean not merely to survive but to flourish.

The play itself, though, still ails; like most one-person shows, it needed a second opinion.