“Parrotheads” and casual fans of Caribbean living mourned the death of “Margaritaville” singer Jimmy Buffett over the weekend, who died at the age of 76 after a years-long battle with a rare and aggressive form of skin cancer on Friday.

After Buffett’s death, his website revealed that the singer and businessman had died from Merkel cell carcinoma, a form of skin cancer that is considered three to five times more deadly than melanoma.

Here is everything you need to know about Merkel cell carcinoma:

How rare is Merkel cell carcinoma?

According to the Skin Cancer Foundation, around 3,000 people in the United State are diagnosed with Merkel cell carcinoma every year. That equals around one case for every 130,000 people.

Merkel cell carcinoma is also 40 times more rare than melanoma, a more common deadly form of skin cancer.

Who is at risk of Merkel cell carcinoma?

Like most skin cancers, Merkel cell carcinoma usually forms as a lump on sun-exposed skin. Areas such as the head and neck, as well as the arms, legs and trunk are the most impacted, according to the National Cancer Institute.

Risk factors include sun exposure and a weakened immune system. People over the age of 50 are also more likely to contract Merkel cell carcinoma as well.

What does Merkel cell carcinoma look like?

Merkel cell carcinoma is a lump that is usually painless, fast-growing, firm or dome-shaped and violet or red in color. The cancer is usually detected during a skin exam, which you can do on your own or with a doctor.

If you think you have an unusual lump growing on your skin, seek a dermatologist as soon as possible.

How is Merkel cell carcinoma treated?

Merkel cell carcinoma is treated like most cancers. First, the cancer is diagnosed and determined to be in a stage between 0 to IV, depending on how large the tumor has grown and how much the cancer has spread throughout the body, if at all.

The tumor will have to be surgically removed, and nearby tissue and lymph nodes may be removed as well.

Cancer can spread through cells in tissue and lymph nodes. Cancer can also spread through the body if it gets into the bloodstream.

After surgery, patients may receive chemotherapy, radiation and/or immunotherapy to completely rid the body of cancer.

What is the outlook for Merkel cell carcinoma?

Merkel cell carcinoma is a rare and aggressive form of skin cancer that has a high likelihood of spreading and recurrence.

According to the American Cancer Society, people diagnosed with Merkel cell carcinoma at any stage are “about 70% as likely as people who don’t have that cancer to live for at least 5 years after being diagnosed.”

However, survival rate is highly variable. The earlier the cancer is detected, the better.

How can Merkel cell carcinoma be prevented?

The best way to prevent Merkel cell carcinoma is to protect skin from the sun and its ultraviolet (UV) rays.

To limit sun exposure, always seek shade and follow what the American Cancer Society calls “Slip! Slop! Slap! … and Wrap!” Meaning:

  • Slip on a shirt.
  • Slop on sunscreen.
  • Slap on a hat.
  • Wrap on sunglasses to protect your eyes and the sensitive skin around them.

It is also advised not to use tanning beds or sun lamps.

Hollywood is mourning the loss of an icon. Following the heartbreaking news that legendary “Margaritaville” singer Jimmy Buffett has passed away at the age of 76, celebrities took to social media to share their condolences.