The blemish on her shoulder was actually a Bednar tumor, a type of soft-tissue sarcoma.

By Amanda MacMillan
February 13, 2019

If you had a bruise that wasn’t going away, how long would it take you to get it checked out? One woman, featured in this week’s BMJ Case Reports, waited six years before seeing her doctor about a mysterious blemish on her left shoulder—and when she finally did, she received quite a shock: Her stubborn bruise, it turns out, was a rare type of skin cancer.

The woman’s doctors, at the Hospital de Braga in Portugal, wrote about their experience as a heads-up to other physicians. “We reported this case because of its rarity and unusual presentation,” they wrote in the medical journal. This type of tumor can be mistaken for other skin conditions, they point out, so a thorough examination and proper testing is always important in situations like these.

Here’s how it all went down, according to the case report: When doctors first took a look at this 31-year-old woman’s “hyperpigmented lesion,” they referred her to the hospital’s department of dermatovenereology—a department that deals with skin conditions related to sexually transmitted infections. The spot was tiny—only about a centimeter in diameter—but the woman reported it had progressively gotten larger over the last six years. She also couldn’t recall any particular trauma that could have caused a bruise in the first place.

BMJ Case Reports

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When they examined her skin under a microscope, however, the doctors noted that the lesion had a purplish background with “blue-whitish veil lesions,” an indicator that a growth might be cancerous.

A biopsy confirmed their suspicions, and a specialist diagnosed the lesion as dermatofibrosarcoma protuberans (DFSP), a rare, slow-growing form of skin cancer that begins in the middle layer of skin, known as the dermis. According to previous research in the United States, the incidence of DFSP is between just 0.8 to 4.5 cases per million people per year.

This specific type of “pigmented DFSP”—known as a Bednar tumor—is even more rare, making up only about 5% of all DFSP cases. Even though DFSP tumors don’t usually spread to other organs, they can grow deep into fat, muscle, and bone, according to the American Academy of Dermatology, which can destroy tissue and make treatment difficult.

Luckily, a CT scan showed no cancer elsewhere else in the patient's body, and the tumor was successfully removed via surgery. Her doctors say they’re following up with her regularly, and two years later she’s still cancer-free.

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The authors of the case report say it’s important for doctors to be aware of DFSP and Bednar tumors, which tend to occur on the back and shoulders and are most common in men and women in their 40s and 50s. “[A]ny lesion with a prolonged evolution or that does not resolve spontaneously, even if clinically unsuspected, should always be biopsied to exclude malignancy,” they wrote.

And while their case report is directed mainly at doctors, it can also serve as a reminder for us patients as well: This particular patient's experience highlights a rare (and thankfully, non-aggressive) form of skin cancer, but DFSP isn’t the only condition that can resemble a bruise. Melanoma, the deadliest form of skin cancer, can as well.

There may also be other medical reasons a person is bruising easily or a bruise is taking longer than usual to heal. The bottom line: Any strange marks that don’t go away on their own are worth a visit to the doctor. As this patient learned, it’s better to be safe than sorry.

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