A pseudoangiomatous stromal hyperplasia (PASH) is a benign (harmless) lesion found in breast tissue. Mostly made from collagen, which is also known as stromal cells, a PASH can often be felt as a lump during a routine breast exam. The first documented case of a PASH was in 1986.
PASH is found in 23% of all breast tissue. These non-cancerous lesions are common and most women have one at some point in their lives.
Why Is PASH Mistaken for Cancer?
Sometimes, pseudoangiomatous stromal hyperplasia is mistaken for an angiosarcoma — a rare form of cancer that can develop in blood vessels, including those in the ones in the breast. But benign PASH lesions aren't likely to become cancerous and aren't consistently found along with breast cancer tumors.
Your doctor needs to be able to distinguish between PASH and cancer. Once your mammogram — or breast X-ray — has shown something that looks like PASH, your doctor must be absolutely certain of the diagnosis before telling you that you don’t have cancer.
Who Gets PASH?
Pseudoangiomatous stromal hyperplasia is most often found in women between ages 30 and 50. But there have been cases of PASH among girls as young as age 14 and women between ages 51 and 67.
PASH can also be found in men, though this is most often in men with gynecomastia — a condition that enlarges breast tissue, mostly in pubescent boys.
What Is the Cause of PASH?
While the causes of pseudoangiomatous stromal hyperplasia aren't well understood, some evidence suggests that PASH formation is linked to hormones. The breast lesions can grow in coordination with your menstrual cycle, and they only occur in men with gynecomastia, which is a hormonal condition. There are also a limited number of cases that link PASH formation to the use of oral contraceptives and hormone replacement therapy.
More research is needed to figure out exactly what causes PASH.
What Are the Symptoms of PASH?
The most common type of PASH lesion is microscopic and generally symptomless — so you won't know it’s there. The larger ones, which are usually between one centimeter to 12 centimeters in size, are round or oval masses that will feel like a lump when you touch them. PASH lesions are mainly discoverable during routine mammograms.
Larger PASH lesions can change in size, sometimes quite quickly. They're able to move around in your breast tissue so you won't always find them in the same place.
A PASH lesion shouldn't cause you any pain or discomfort, but might if they become too large. This change in size isn't life-threatening, though.
How Is PASH Diagnosed?
Your doctor can properly diagnose a breast lesion with:
- A mammogram or magnetic resonance imaging (MRI). These visual tools are used to examine breast tissue.
- An ultrasound. Breast tissue is examined using sound waves.
- A core biopsy. A hollow needle is used to remove a sample of breast tissue and examine it under a microscope.
- Surgical removal. An entire lesion may be removed if it's too difficult to determine whether it's a PASH.
What Is the Treatment for PASH?
Most of the time, you won't need any more treatment after being diagnosed with PASH. Your doctor will simply want to follow up during your annual mammogram.
In rare cases, you may want to have surgery to remove the lesion. You could decide to have this surgery because your PASH has become too large and you are having discomfort from the size. Your doctor may also need to remove the lesion if there's no other way to be sure that it’s PASH.
During this simple procedure, the cells that make up the lesion are removed along with a portion of the surrounding tissue to prevent the lesion from growing back. There's only a 15% to 22% chance that a PASH lesion will return after the surgery.
