With thousands of posts on this site stretching back nearly 5 years, you’d assume the most engaging topic would be something like this:

“I have a lump in my breast, what could it be?”

Or, “What’s chemo like?”

Or conversation around a tough decision, like “Should I have a lumpectomy or a mastectomy?”

While these topics would be expected to generate reader interest and response, none comes close to one single thread, begun April 26, 2008, by “Joni,” who wrote as follows:

“Strange, my left breast ‘vibrates’ every so often, sort of like a cell phone that's on vibrate! For the last three days my left breast has this strange vibration. At first I thought I was imagining it but it continues! It doesn't hurt… just feels weird. Could it be a symptom of breast cancer?”

Since then, 135 responses have been added to the thread. Men, women, and teenagers report this strange sensation, most often saying, as Joni did, that it feels like a cell phone vibrating.

Readers have reported underlying medical conditions from multiple sclerosis, to obesity, to acid  reflux syndrome, poor posture, chiropractic issues, vitamin B12 and vitamin B6 deficiency… to being a breast cancer survivor, and fearing this is a sign of recurrence.

Some have reported consulting a doctor, and have gotten these responses:

It’s an after-effect of shingles. The result of a hematoma. A reaction to the titanium clip used in a guided biopsy.

Two readers report that they later discovered cancer in their vibrating breast. One added that her oncologist said the vibration had nothing to do with her cancer.

One reader is sure the vibration is related to the magnetic/electronic field of laptop computers.

What’s the story here? Is there a good explanation for The Strange Case of the Vibrating Breast?

Nope. Just like research around the causes of cancer, there’s lots of speculation, but no definitive answer.

I’ve done extensive online research, and have come up with the following, which at least seem like reasonable possibilities:

•Fasciculation – a tiny twitching of the muscles in the chest wall, cause unknown, though possibly related to anxiety. Can be felt as a vibrating sensation in the breast.

•Contractions of the tiny muscles surrounding the milk ducts in the breast. Cause unknown, though the theory is they could be due to a temporarily blocked duct. No relation to breastfeeding.

•Spasms of the tiny blood vessels in the breast. Again, cause unknown.

Dr. Martee L. Hensley, a medical oncologist at Memorial Sloan-Kettering Cancer Center in New York, responded to a reader question on everydayhealth.com as follows:

“While feeling vibrations in the breast is a rather uncommon complaint, these sensations have not been associated with any serious condition. It is sometimes hard to pinpoint an exact cause… [but it’s] highly unlikely that there is cause for alarm, whatever the specific explanation.