Tennis legend Serena Williams has had some terrifying health scares in her time. In 2011, on her way to an Oscars party, she suffered a pulmonary embolism, a blood clot in her lung.

“I was on my death bed at one point – quite literally. I’ve had a serious illness but at first I didn’t appreciate that,” she said at the time.

In 2018, blood clots returned to her lungs after the birth of her daughter. In that instance, she was aware of what was happening before the doctors were. At first they didn’t believe what she was saying. Again, she could have died.

Her latest scare happened in May: A lump appeared on her neck.

It made her look like she was trying to swallow a tennis ball. Lumps are always a little scary, but her doctors quickly recognised this wasn’t cancer.

As Williams said on TikTok: “In May I found this big mass on my neck. I was mortified by it and got tested. Everything was negative (benign). Turns out I had what’s called a branchial cyst … it was so big, the size of a grapefruit.”

She said she was feeling “a little scared here”. She was also in great discomfort.

Some people may have assumed that the widely-seen images of Williams grimacing in pain were taken during the operation to remove the cyst. Not so, she was deeply sedated during the procedure.

The images of Williams in pain were taken when a drain was being placed in the wound, and remained there for a couple of days.

At last word, she was doing well, and was out and about with her daughter.

In Williams’ mind, perhaps, the cyst was a recent development. In fact, being a congenital condition, the cyst had been with her from before she was born.

So will it comes back? Maybe. Surgery usually results in a good outcome. However, cysts can recur, especially if surgery happened during an active infection.

What is a branchial cyst?

Branchial cysts are small fluid-filled sacs that may look like lumps under your skin on the side of your neck or just below the collarbone.

More fully known as a ‘branchial cleft cyst’ – or ‘branchial cleft anomalies’ – they appear at any age but are often found in children.

According to the Cleveland Clinic, it’s not known if they’re rare or common because they often remain invisible and cause no problems. On the other hand, branchial cleft cysts are one of the most common forms of neck masses or lumps, especially in children.

According to a 2013 article in the US National Library of Medicine, if the cyst does grow then it usually happens slowly, over a period of weeks or even years.

Depending on the size (which ranges from 1 to 10 cm) and location, the cysts can produce symptoms such as:

• Difficulty swallowing (dysphagia)
• Having an abnormal voice (dysphonia)
• A sensation of running out of air and of not being able to breathe fast enough or deeply enough (dyspnea)
• An abnormal, high-pitched, musical breathing sound (stridor).

The cysts can become painful or tender when infected. When people develop noticeable branchial cleft cysts later in life, it’s usually because of infection.

Cancerous tumors may develop at the site of a branchial cleft in adults, but this is very rare.

How they develop in embryos

Branchial cleft cysts happen early in your development as an embryo, when your body is building the foundation for your head and neck structure.

This includes your voice box, upper jaw and your hyoid bone, which supports your tongue.

Here, according to the Cleveland Clinic, is how the process works:

• Neural crest cells, which develop tissues, gather in the area of your head and neck to create what’s called your branchial apparatus
• Your branchial apparatus becomes cartilage, bone, blood vessels and the muscles in your head and neck
• Your branchial apparatus has ridges of tissue (arches) and in-foldings of tissue (clefts) that are responsible for developing certain parts of your head and neck. All told, there are six arches and five clefts
• Branchial cleft cysts happen when branchial arches don’t fuse, or grow together, leaving tiny spaces. Branchial anomalies develop in these spaces.

They’re more of a quirk in your development, rather than a structural vulnerability. Most of us will never know if we have them.