When we talk about breast cancer, we rarely talk about the men who are diagnosed with the condition.

So often, we assume breast cancer is exclusively a women’s disease, says Dr. Kristen Fernandez, medical director of the breast center at the MedStar Franklin Square Medical Center in Maryland.

“Men think they don’t have breast tissue, but they do,” she explains to MensHealth.com.

Guys have less breast tissue than women do, so their risk of developing breast cancer is comparatively more rare. In fact, guys make up less than one percent of breast cancer cases.

But the risk of a man developing breast cancer still exists, and Fernandez says many men often ignore the symptoms.

While guys don’t necessarily need to perform regular self breast exams, Fernandez strongly believes that guys should occasionally check for pain or lumps in their breast tissue. And if you do experience pain, “don’t ignore it” and see a doctor right away, she says.

In advance of Breast Cancer Awareness Month this October, here are four symptoms of breast cancer that guys should watch out for.

1) Lumps

Guys often ignore lumps on their chest, thinking they may have just bumped themselves while doing yard work, says Fernandez. But a lump in your pecs can be a sign of breast cancer. Typically painless, these lumps can be accompanied by tenderness in the area, especially when touched, she says. If the cancer has spread, swelling can be found under the armpit, in the lymph nodes, or around the collar bone.

2) Inverted nipple

As a breast cancer tumor grows, it begins to pull on ligaments inside the breast, causing the nipple to invert or become dented, Fernandez explains. Sometimes, the inverted nipple will be accompanied by dry, scaly skin in the area.

3) Nipple discharge

Guys may notice stains on their shirts and simply chalk them up to spills, says Fernandez. But if stains always appear on the same side of the chest, then it could be nipple discharge. This happens because fluid from the tumor builds up and leak out of the nipple duct.

4) Open sores

In extreme cases, men may develop an open sore on the nipple because the tumor is “almost growing through the skin,” says Fernandez. “That’s a cancer that’s sort of been ignored,” she explains. Since men have very little breast tissue, it’s possible for the tumor to push through the skin. The sore will look like a picked pimple, she says.