Sarcoma is a word derived from the Greek word “sarc,” meaning flesh or soft tissue. It defines a group of malignant tumors that occur mostly in muscle, fibrous tissue, adipose, nerve and vascular tissue. 

The most common type of pediatric sarcoma is rhabdomyosarcoma, a tumor of the skeletal muscle. As children grow older, sarcomas are more likely to be found in bone.

“Pediatric sarcomas are rare, but when they occur, an expedited diagnosis means expedited treatment,” says Raffaella Morotti, MD, a Yale Medicine pathologist in the Department of Pathology.

Depending on the patient’s symptoms, which may include bone pain or the swelling of soft tissue, several diagnostic possibilities may be suggested.

These may include imaging tests such as a computerized tomography (CT) scan or magnetic resonance imaging (MRI). While those images may suggest to the radiologist the diagnosis of cancer, “The standard of care demands that the definitive diagnosis be made by a pathologist,” Dr. Morotti says. This usually means a biopsy will be taken.

A surgeon performs a biopsy by removing tissue from the lump, which is then sent to a pathologist. "From this tissue, a multistep process begins, which can take a few hours to a whole day, as glass slides are generated and analyzed under the microscope," Dr. Morotti says. 

The first look uses a coloring method called hematoxylin and eosin, which stains components of the tissue, turning them pink or blue. “This is done routinely in all labs for all tissue samples and allows the pathologist to determine whether the lesion is likely benign or malignant,” Dr. Morotti says.

Additional steps are taken to confirm the diagnosis. “Pathologists use more specific and sophisticated stains called immunostains, which allow us to be more precise in diagnosing the specific type of sarcoma,” Dr, Morotti says. 

Further tests may be requested by the clinician. These may include molecular diagnostics and/or genetic testing and tumor profiling in order to support the diagnosis and also to guide a targeted treatment plan for the child. Diagnosis typically takes from one to three days, depending on the complexity of the case.

Sarcomas are not very common. Therefore, pathologists who aren't specialized in soft tissue or pediatric tumors may not be accustomed to making such a diagnosis.

“For example, a breast or prostate cancer will be diagnosed every day,” Dr. Morotti says. “But a pediatric sarcoma, even at a busy children's hospital, may occur, at maximum, once a week – and usually much less frequently than that.”

Yale Medicine takes a multidisciplinary approach, involving discussions among pediatric oncologists, radiologists, pathologists and surgeons as well as a team of sub-specialized pediatric and soft tissue pathologists.

“Our pathology team can provide a diagnosis in a time-efficient manner and recommend the appropriate additional tests needed to ensure treatment is less toxic and more successful," says Dr. Morotti.