What is PASH?

Pseudoangiomatous stromal hyperplasia (PASH) is a rare, benign (noncancerous) breast lesion. It can present as a dense mass which can only sometimes be felt when palpating the breast. That mass is caused by an overgrowth of myofibroblastic cells. These are a cross between cells found in connective tissues and cells found in smooth muscles. While infrequent, PASH can also manifest itself with severe breast enlargement.

Even when PASH does produce a palpable mass, it’s often painless. That’s why the condition is usually found incidentally, such as during a routine mammogram.

PASH affects mostly women and can occur at any age, but it’s generally found in women during their premenopausal or perimenopausal years.

In some cases, a PASH mass is microscopic and produces no symptoms. However, PASH can also present as a larger mass. When the mass can be felt, it’s usually firm and moveable.

One study noted that only one-third of people with PASH will experience pain. Eight percent of the study subjects also had a bloody discharge from their nipples.

The cause of PASH is unknown, but experts suspect there may be a hormonal link. Research published in the journal Modern Pathology found that 62 percent of study subjects were premenopausal women, and 73 percent of the subjects used oral contraceptives or hormone replacement therapy. In another study, 90% of the study subjects were premenopausal or perimenopausal.

According to research out of the Mayo Clinic, the answer is no. In fact, the study found that women with PASH had a lower risk of breast cancer, though they cannot explain why. The study looked at over 9,000 biopsies undertaken on women with benign breast disease. While women with PASH tended to be younger than the other study subjects, the two groups had similar family medical histories when it came to breast cancer.

In many cases, PASH is a diagnosis that is made incidentally. A diagnosis often occurs when a woman is having a routine mammogram or undergoing a breast biopsy for another breast condition, such as a fibroadenoma. (Fibroadenoma is another type of painless breast lump that can be confused with PASH.)

Whenever a breast lump is discovered, it’s best to check in with your doctor. Your doctor may order additional imaging tests, such as an ultrasound or MRI. Your doctor may also suggest you undergo a core needle biopsy. This is a procedure, usually done using a local anesthetic to numb the area, in which a hollow needle is inserted into the breast to remove tissue for sampling. The sample is then sent to a lab for evaluation and a definitive diagnosis.

For PASH masses that are not producing symptoms, your doctor may recommend a wait-and-watch approach. The masses do tend to grow over time, and regular follow-up (often with mammography) is advised.

Some women may prefer to have the mass removed. This may be a good option if you have a family history of breast cancer, if the mass is large and causing symptoms, or if it’s just generally making you uneasy. This is typically done via a lumpectomy. A lumpectomy is a surgical removal of the mass and some surrounding tissue. The procedure is performed under general anesthesia, usually in an outpatient center.

Even with removal, PASH can return. Up to 7 percent of people will have a recurrence of PASH. Surgeons often cut out a wide margin of healthy tissue around the mass to help prevent a regrowth.

PASH is a rare condition. Research from the journal Breast Care notes that fewer than 200 cases have been reported since the late 1980s, when it was first identified. It’s generally harmless and asymptomatic.

Because the condition can mimic breast cancer as well as noncancerous breast lumps like fibroadenomas, it needs investigation, evaluation, and follow-up. Make an appointment with your doctor at first notice of a breast lump, and follow recommended guidelines for mammograms.