Jasmine Mamiya was in udder disbelief.
Still recovering in the hospital after giving birth, the mom-of-two thought she’d seen it all — until a lactation consultant casually informed her she’d sprouted an extra breast, complete with a nipple, in a place no one expects.
“You know how cows and puppies and kittens, they have that line of nipples? Yeah, humans have that too,” Mamiya recalled being told in a now viral TikTok. “I think I had like maybe three hours of collective sleep in the last two days before she tells me this news.”
And she gamely showed it off to help other women learn more about their own bodies.
The jaw-dropping discovery came when the consultant dropped by Mamiya’s room shortly after she’d given birth, a standard practice meant to help new moms get the hang of breastfeeding.
“I breastfed my first baby for one and a half years, so, you know, I was thinking there’s nothing this nurse can say that’s gonna surprise me,” Mamiya said.
But as the two chatted, the consultant mentioned that some women develop extra breast tissue during pregnancy along what doctors call the “milk line.”
The invisible strip of tissue runs down both sides of the body from the armpits to the groin. Everyone has it in the womb, but some people are born with tiny amounts of leftover tissue that stay dormant for years.
Pregnancy, however, flips the switch. A surge of hormones targets breast tissue receptors to prepare for feeding, and because the extra tissue is biologically identical to regular breast tissue, it can swell at the same time, sometimes forming lumps complete with extra, or supernumerary, nipples.
Mamiya had already suspected she’d developed some of this excess breast tissue after noticing a stubborn patch of fat under her armpits that wouldn’t go away.
“It got, like, way darker — like when you’re pregnant your nipples and areola will get really dark, and I’ve noticed the same change with my armpits, so I was like ‘Great, extra breast tissue, I already knew that,’” she said.
But when the consultant asked to take a look, it took just one glance to realize things had gone to another level.
“She’s like ‘Yeah, you have a third nipple on your armpit,’ as if that’s like, cute or something,” Mamiya said, admitting she’d assumed the small dark spot was just a skin tag.
“Telling me that I have an extra nipple on my armpit before I even had my first postpartum poop is diabolical work.”
Mamiya’s revelation sent the internet into a frenzy, racking up more than 3.7 million views in a matter of days. Viewers flooded the comment section, stunned, curious and begging for a peek at her third breast.
“You’re not even gonna buy me dinner first or anything, you just wanna see my underarm boob?” she joked in a follow-up TikTok. “That’s crazy but I’ll show you.”
Lifting her arm, Mamiya revealed the bulge tucked inside her armpit, which is apparently the most common place for this so-called “accessory breast tissue.”
“It basically just looks like a little bump and the area around it got darker,” she said of the nipple, noting it wasn’t there before she gave birth. “If I have my arms down it looks normal.”
Naturally, users had questions, including whether the extra tissue could produce milk. Spoiler: It sometimes can. But Mamiya has no plans to test that theory.
“If you think I’m gonna stick my breast pump right here and pump my armpit, you are out of your godd—n mind because no,” she said.
“If you pump, you can stimulate milk production,” Mamiya explained. “I am not trying to encourage milk to come out of there.”
She noted, however, that if she goes too long without breastfeeding normally, the lump gets “angry,” swelling and becoming tender. Fortunately, staying on schedule with breastfeeding and pumping has helped keep it under control, along with ice and heat.
For some women, extra breast tissue shrinks once pregnancy hormones fade, but stretched skin and fatty tissue don’t always return to their pre-pregnancy state.
“My only option is to cut her off I fear, so once I’m done having kids, I can surgically get it removed,” Mamiya said, adding that “there’s nothing you can do about the nipple.”
“If she comes, you will accept her,” she quipped. “Those are the only options.”
And while sprouting a surprise third boob wasn’t on her 2026 bingo card, Mamiya said it’s not the worst postpartum curveball.
“Who cares? You’ve got a third boob, a fourth boob, it’s really kind of the best case scenario of all medical body changes that go on pre and post baby,” she said.
Mamiya, who regularly shares content about mental health and the realities of motherhood, said she posted the video to shine a light on the less-talked-about side of pregnancy and life after it.
Judging by the response, she struck a nerve. Both videos were filled with comments from moms who’d experienced similar anatomical changes — a club Mamiya dubbed “The sisterhood of the 3rd nipple.”
“As women and especially mothers, our vulnerability is our strength. There’s so much that’s not talked about and understudied, sharing our experiences honestly and transparently is what will combat that,” Mamiya told The Post.
“There is no experience that millions of women before you have not already gone through, like having armpit boobs!”
