Endometriosis for Men: Why Understanding This Rare Condition for Men Matters for Women (as well)

When most people hear endometriosis, they think of women in their reproductive age, battling pelvic pain, chronic fatigue, or fertility struggles. The word itself comes from the endometrium — the uterine lining, which is why the idea of endometriosis in men sounds like a medical mix-up, or maybe the setup for a strange joke.

And yet, medical literature tells us otherwise. Endometriosis occurs — albeit incredibly rarely — in men. The best number I could find was from a 2018 review that mentions 16 reported cases of endometriosis in cis-men exist worldwide. That makes every male patient diagnosed with endo rarer than a four-leaf clover in a concrete parking lot.

So what does this mean? Well, if you’re a man reading this and have been told (unbelievingly) you’re the 17th case of documented endo in men, you can officially believe it. It does happen.

Although male cases of endometriosis are exceedingly rare, they offer profound insights into the nature of the disease—demonstrating that it isn’t merely a menstrual or uterine issue. While endometriosis primarily affects individuals with uteruses, these unusual cases in males—and, occasionally, in women born without uteruses—serve as powerful reminders. Endometriosis is fundamentally an immune-mediated, inflammatory condition that, under specific circumstances, can affect anyone.

Endometriosis in Men: What We Know So Far

A male endometriosis diagnosis almost always comes as a highly unexpected diagnosis. Reported cases describe endometriotic tissue found in places like the urinary bladder, lower abdominal wall, tunica vaginalis, vas deferens, and even the inguinal region (this is what the literature says; the simple understanding is in the male reproductive system).

Instead of following the pattern we see in the female genitourinary tract, endometriosis in a man seems to develop where embryonic cell rests may have been left behind during fetal development. These remnant embryological cells, dormant for decades, can be stimulated under the right conditions — usually involving prolonged estrogen therapy or prolonged hormonal therapy.

This is why many case reports involve men undergoing estrogen therapy for prostatic carcinoma (prostate cancer). Prolonged exposure to elevated estrogen levels acts as the prevailing risk factor. Add in things like liver cirrhosis (which reduces the liver’s ability to clear estrogen), increased obesity (since adipose tissue produces estrogen), or chronic surgical inflammation — and the risk factors start stacking.

Abdominal Pain and Other Symptoms

What does male endometriosis actually feel like? I was super curious about this. Turns out, this is kind of similar too. The symptoms mirror women’s experiences, minus the menstrual cycle connection:

• Abdominal pain or lower abdominal pain — often a constant dull ache that flares into sharp, intermittent discomfort.

• Chronic pelvic pain and lower abdominal pain radiating to the groin.

• Scrotal pain and swelling linked to tunica vaginalis involvement.

• Blood in urine when endometrial tissue grows in the urinary bladder or lower genitourinary tract.

• Palpable masses in the inguinal region or lower abdominal wall.

In almost every case report, the location of symptoms matches where the tissue resembling endometrial glands has implanted.

Male Endometriosis: The Science Behind It

So how can a man develop tissue that looks like endometrial glands and underlying stroma? Several theories exist:

• Embryonic cell rest theory: During fetal development, the mullerian ducts in males normally regress under the influence of anti mullerian hormone. But if embryonic cell rests remain behind, they can later differentiate into endometrial epithelium and endometrial glands when exposed to estrogen.

• Induction theory: Prolonged estrogen treatment or prolonged hormonal therapy can activate dormant embryonic cells, essentially coaxing them into behaving like uterine lining.

• Inflammation triggers: Chronic surgical inflammation or repeated trauma may also serve as a causative factor, with proinflammatory cytokines creating the environment for abnormal growth.

Together, these theories show that male endometriosis isn’t a total mystery — it’s simply a rare twist on the same disease process that affects women.

It's realy very similar to developing endo with us ladies: it starts with a cell, perhaps misplaced at birth. But that cell is not a lesion until it's activated into endometriosis thanks to an inflammatory soup of macrophages, cytokines, estrogen, and more (I talk all about this in my book, the many steps of developing endo, from cell to lesion). The difference is that it'sincredibly rare with men since they would need to have a rogue endometrial tissue laid down in utero, whereas we women pretty much always have it (unless we're born without a uterus).

Risk Factors in Male Patients

Across the cases I could find, the main contributing factor is clear: estrogen exposure.

Documented risk factors include:

• Prolonged estrogen therapy or prolonged estrogen treatment for prostatic carcinoma.

• Elevated estrogen levels due to liver cirrhosis.

• Increased obesity, leading to increased estrogen production from adipose tissue.

• Insulin resistance and metabolic dysfunction.

• Family history of ovarian cancer.

• Chronic surgical inflammation and inadequate immune function.

While most men never face these risk factors, each case report gives insight into how hormonal alterations and immune dysregulation interact with embryonic cell rests (that fancy word to mean where the uterine cell might have been accidentally placed in utero).

How Is Male Endometriosis Diagnosed?

Because endometriosis in men is so rare, it turns out most diagnoses usually happen by accident, during surgery for or when investigating a palpable mass in the reproductive region or lower abdominal wall.

I mean, what doctor is going to even think their male patient has endo??

Diagnosis would then be to remove the tissue and look under a microscope to see what it is.

Treatment and Outlook: Looking good

Most reported cases show resolution after surgical removal or surgical resection of the endo tissue. Especially when combined with stopping estrogen therapy for prostate cancer, outcomes are positive. Some case reports even note that tissue may atrophy completely once estrogen stimulation is removed.

Because male endometriosis is so rare, treatment guidelines don’t really exist. Each male patient is managed on a case-by-case basis. But the overall prognosis? Excellent.

What Male Endometriosis Teaches Us About Endo

Here’s where we zoom out. Why does it matter that a few men on the planet have developed endometriosis?

Because it proves that:

• Endometriosis is not just about fallopian tubes or reproductive age.

• Endometriosis hypothesizes a disease driven by immune dysfunction and chronic inflammation.

• Risk factors like inadequate immune function, prolonged exposure to estrogen, and environmental triggers matter more than gender. If you have the ingredients (cell + inflammation + estrogen) it looks like anyone can have endometriosis.

In other words, male endometriosis underscores what endo patients have been saying all along: this is a whole-body disease, not just “bad periods.”

Conclusion: A Rare but Important Story

Endometriosis in men will probably never be a common headline. With only a handful of reported cases, it’s more a medical curiosity than a widespread issue.

But for every male patient who has endured abdominal pain, scrotal pain, or unexplained masses until finally receiving this highly unexpected diagnosis, the story matters. Their experience adds to our collective understanding of endometriosis.

And for the millions of women with endo? Male endometriosis validates what the science — and your lived experience — already shows: endometriosis occurs when endometrial tissue takes root outside its usual home, fueled by hormones, immune dysregulation, and systemic inflammation.

So maybe the biggest gift of male endometriosis is perspective. It reminds us to stop minimizing endo as “women’s trouble” and start respecting it as the complex, inflammatory condition it is — one that deserves compassion, curiosity, and better answers for everyone.

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