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Tattoo ink mimics cancer in scan

June 17, 2015 | John Murray
Tattoo ink mimics cancer in scan
Image of lower extremity tattoos from case study Tattoo and False-Positive PET Scan. Obstet Gynecol 2015.

File this under "Medical Oddities."

A 32-year old patient with cervical cancer undergoes a specialized scan before surgery to determine whether the disease has metastasized. Several lymph nodes lit up in the scan – usually an indication that malignant cells have spread.

A surprising culprit

After surgery, the physicians take a closer look at the nodes and don’t find any cancer. The culprit? More than a dozen lower body tattoos, according to a case study published this month in the journal Obstetrics & Gynecology.

“Those lymph nodes that were lighting up brightly on the PET scan were doing so because of the tattoo pigment,” study co-author Dr. Ramez Eskander, an assistant professor in the UCI Health Department of Obstetrics & Gynecology, recently told the online magazine Live Science.

Gynecologic oncologists increasingly use positron emissions tomography fused with computed tomography, known as PET/CT scans, before surgery to evaluate metastatic cancer. Numerous studies show the scans are much more specific and sensitive in detecting cancer harbored in lymph nodes compared to CT alone or with magnetic resonance imaging.

Possibility of false positives

The takeaway for cancer specialists, Eskander says: Physicians must be aware of the possibility of a false-positive PET/CT scan in patients with tattoos. A failure to realize the scan is a false-positive may subject the patient to unnecessary chemotherapy and radiation.

The study notes other reports describing the migration of tattoo ink to some lymph nodes in patients with breast cancer and melanoma, among other cancers. This can make it difficult to easily differentiate between the ink pigment and the metastatic disease.

And how did tattoo ink get into the lymph nodes? Eskander’s review suggests that her tattoo pigment may have migrated to the lymph nodes after being engulfed by a type of cell called a macrophage.

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