An Extra-gastrointestinal Stromal Tumor Masquerading as an Adrenal Mass: A Case Report and Review of the Literature

In the deep space of the human body, tucked behind the stomach and kidneys, lies a region called the retroperitoneum. It is a quiet, crowded neighborhood where the body's major blood vessels run and where the adrenal glands sit like small, triangular caps atop the kidneys. These glands are vital chemical factories, pumping out hormones that control blood pressure and stress. Because of their location and function, doctors are trained to be wary of any new lump that appears there. Often, such a mass is assumed to be a tumor originating from the adrenal gland itself, a dangerous growth that requires immediate and specific attention. However, the body is full of surprises. Sometimes, a tumor does not start in the organ it seems to be pressing against, but rather grows in the soft tissue nearby, mimicking the appearance of its neighbor so perfectly that even advanced imaging cannot tell them apart. This is the story of a rare tumor that masqueraded as a glandular cancer, and the careful journey doctors took to uncover its true identity.

The case began with a seventy-four-year-old woman who arrived at the emergency department complaining of pain in her left side. A scan of her abdomen revealed a large, solid mass sitting right above her left kidney. The image showed a growth measuring 5.8 by 6.1 by 4.9 centimeters, with a messy, uneven texture and a dark center where tissue had died. To the radiologist, this looked exactly like a primary adrenal cancer, a condition known as adrenocortical carcinoma, or perhaps a tumor of the adrenal gland that secretes stress hormones. The medical team moved quickly to rule out the most dangerous possibilities. They ran a battery of blood and urine tests to check for the hormones these tumors typically produce. The results were clear: the patient's body was not flooding with stress hormones or other adrenal chemicals. The mass was not acting like a hormone factory. Further scans of her chest showed no signs that the cancer had spread to her lungs or bones. With the hormonal tests negative and no distant spread visible, the decision was made to remove the mass surgically.

The surgery was performed using a robot-assisted approach, a technique that allows surgeons to operate through tiny incisions with high precision. The team worked from the back, entering the retroperitoneal space to reach the mass without disturbing the front of the abdomen. They carefully separated the large lump from the surrounding blood vessels and organs, including the spleen and the stomach. They also removed nearby lymph nodes to check for any hidden spread of disease. The entire procedure was successful, with minimal blood loss, and the patient was sent home just two days later. But the true story of the mass was not revealed until the pathologist examined the tissue under a microscope.

When the surgeons removed the specimen, they expected to find a cancerous adrenal gland. Instead, they found something entirely different. The large, 7.5-centimeter tumor was not part of the adrenal gland at all. It was a separate growth that had grown right up against the gland, pressing it flat and making it look like a single unit. The adrenal gland itself was healthy and untouched by the disease. The tumor was identified as a gastrointestinal stromal tumor, or GIST. These are rare cancers that usually start in the wall of the stomach or intestines, arising from special cells that help the gut move food along. In this patient, however, the tumor had started in the soft tissue of the retroperitoneum, far from any part of the digestive tract. This is known as an extra-gastrointestinal stromal tumor, or EGIST, a very rare occurrence that accounts for less than five percent of all such cases.

The diagnosis was confirmed by a specific chemical test on the tissue. The tumor cells were glowing positive for a protein called CD117, which acts like a unique fingerprint for this type of cancer. The tests also showed the tumor was negative for other markers that would indicate a smooth muscle tumor, a nerve tumor, or an adrenal cancer. This distinction was critical because the treatment for each of these conditions is completely different. While the tumor was found to be low-grade and slow-growing, with very few cells dividing, the surgery was not perfect. A tiny sliver of the tumor remained at the edge of the cut, a situation doctors call an R1 resection. This means the mass was not removed with a wide margin of healthy tissue, leaving a small risk that it could return.

The case highlights a significant challenge in modern medicine: the difficulty of distinguishing between different types of tumors before surgery. Because the mass looked so much like an adrenal cancer on the scan, the doctors could not have known it was a GIST until after it was removed. This is why a thorough hormonal workup is essential before operating on any adrenal mass; it helps rule out the most dangerous functional tumors. It also underscores the importance of looking beyond the obvious. A large lump near the adrenal gland is not always an adrenal problem. It could be a rare tumor growing in the soft tissue nearby, one that requires a different kind of treatment and a different kind of long-term care.

For this patient, the path forward involves close monitoring and a discussion with oncologists about whether to take medication to prevent the tumor from coming back. The standard treatment for this type of cancer involves drugs that block the specific genetic mutations driving the tumor's growth. However, the doctors noted that they did not yet know the specific genetic makeup of this patient's tumor. Without that genetic map, it is impossible to know for certain which drug would work best or if it is even needed. The medical team emphasized that future cases like this one need to be studied more closely to understand how these rare tumors behave and what the best way to treat them is. For now, the patient is recovering well, having survived a complex surgery that revealed a rare truth hidden inside a common-looking mass.