Breast Oil Cysts: Causes, Diagnosis, and Treatment

Breast oil cysts are benign breast lumps that usually don't require treatment. Similar to simple breast cysts, oil cysts are fluid-filled sacs that may feel smooth and squishy. Caused by the breakdown of fatty tissue, they often occur after breast surgery to either rule out or confirm a diagnosis of breast cancer, and hence, can be alarming. Other causes include trauma or bleeding disorders, though sometimes they occur spontaneously. They may be seen on mammogram, ultrasound, or breast MRI. Breast oil cysts can be left alone, or instead aspirated to remove the cyst. When large, painful, or if the diagnosis is in doubt, surgery may be done.

Digital illustration of a woman's body showing a self breast exam
Ian Hootan / Getty Images

While breast oil cysts do not become cancerous, and do not increase the risk of developing breast cancer, in rare cases they may occur in association with an underlying cancer.


Breast oil cysts are usually found on a self-breast exam. When they are small, they often go unnoticed, or may instead be seen on mammogram. Roughly 25% of breast oil cysts grow larger, and can be felt on exam as soft, squishy, and smooth lumps. They can be painful or painless, and may be associated with bruising if they occur after surgery or trauma.


Breast oil cysts may occur after breast surgery, along with other breast conditions, or even occur spontaneously. They are called oil cysts because they contain a liquid form of body fat.


If you have a lumpectomy or mastectomy, fat tissue may die as your body is healing and attempting to form a scar. Breast fat necrosis (the breakdown of fatty tissue in the breast) can form into hard scar tissue, or it can "melt."

When "melted fat" collects in one area, your body may cause a thin layer of calcium to form around it. This eggshell calcification (the appearance of oil cysts on a mammogram) gives your healthcare provider a clear idea of your diagnosis. Simple and complex cysts do not have the calcium layer, but oil cysts are usually enclosed partially or totally by calcium.


Conditions in which fat necrosis (and hence oil cysts) may occur include:

  • Breast cancer surgery or reconstruction
  • Trauma to the breast: In men, most breast oil cysts are associated with trauma
  • Breast augmentation surgery: Oil cysts are more common when autologous fat grafting (fat taken from another region of the body and placed in the breast) is used
  • Breast reduction surgery
  • Radiation therapy to the breast after a lumpectomy
  • Breast biopsy
  • Breast cyst aspiration
  • Mammary duct ectasia (dilated clogged milk ducts occurring around menopause)
  • Mastitis (a breast infection)
  • Conditions in which bleeding occurs easily, such as during Coumadin (warfarin) therapy, with heparin, with other blood thinners, or with bleeding disorders
  • In association with uncommon conditions such as polyarteritis nodosa or steatocystoma multiplex


If you have noted a lump, your doctor will likely recommend further testing. Testing that may be done include:


Oil cysts often show up on mammogram as a well-defined mass that appears fatty, and eggshell calcifications may be present. These are different than the type of breast calcifications that tend to be associated with breast cancer.

Breast Ultrasound

A breast ultrasound often gives a clearer picture of oil cysts than a mammogram. Ultrasounds use sound waves bounced off of breast tissues to create an image of masses, lumps, and cysts. Because cysts are filled with fluid, gas, or semisolid substances, they appear on ultrasound as dark, smooth-edged circular or oval areas. These cysts have a clear outline that distinguishes them from surrounding tissues. Other types of breast lumps will appear on ultrasound with different characteristics, although a seroma can appear identical to an oil cyst on ultrasound.

Breast MRI

Oil cysts will also show up on a Breast MRI.

Differential Diagnosis

Conditions that may appear similar to a breast oil cyst include:

  • Seromas (seromas are also common after breast surgery)
  • Simple cysts
  • Fat necrosis
  • Lipomas
  • Galactocele (collection of milk)
  • Hematomas
  • Papillomas
  • Breast Abscess
  • Rarely, breast cancer that is breaking down (necrotizing malignancy)

Treatment Options

Oil cysts are benign—they are not cancerous, and they don't increase the risk or cause breast cancer. If you develop a cyst after a procedure such as a lumpectomy, however, it will be important to distinguish an oil cyst from a possible recurrence. There are several options if you are diagnosed with a breast oil cyst.


An oil cyst may be left alone, as many of these will shrink on its own.


If your oil cyst becomes physically painful or causes you worry or distress, it can be aspirated. Your doctor can use a very fine needle to suction the fluid out of the cyst, which will deflate it. Aspirated fluid from an oil cyst will be evaluated to make sure it doesn't appear bloody. Breast oil cysts may recur after aspiration, and the procedure may need to be repeated.


If the cyst is large, has a coarse calcium layer, is painful, or continues to recur, your doctor might recommend surgical removal.

Home Remedies/Natural Methods

If your oil cyst is painful, medications such as Advil (ibuprofen) may be helpful. You should also wear a comfortable bra or camisole. Using an ice pack may also reduce your discomfort.

Bottom Line 

Breast oil cysts are benign, yet since they often show up after breast surgery—whether the surgery was just a scare or instead, a confirmation of breast cancer—they can cause a lot of anxiety. Mammography is the most specific test for breast oil cysts, but breast ultrasound or breast MRI may be helpful in making the diagnosis at times. Treatment options include "watchful waiting," aspirating the cyst, or less commonly, surgically removing the cyst. While treatment is not usually needed, many women (and men, since men can experience this as well) feel more comfortable with aspiration. With cyst aspiration, the oil cysts usually deflate, both resolving the cyst and the anxiety that can accompany having these cysts.

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