Synovial Sarcoma of the Parotid Gland in Infancy: A Rare Case Study

Synovial sarcoma most often develops near the large joints of the arms or legs, but in rare cases it can arise in the head and neck region. An especially uncommon presentation occurs in infants. A recently published case report describes synovial sarcoma originating in the parotid gland—the salivary gland located near the jaw and ear—in a 10-month-old child.

While synovial sarcoma is already considered a rare cancer, cases like this highlight how the disease can present in unexpected locations and at very young ages, creating unique diagnostic and treatment challenges.

A rare and unexpected presentation

In this case, the infant presented with a firm, painless swelling in the parotid region that gradually increased in size over several months. There were no early signs of facial nerve involvement, difficulty feeding, or other symptoms that might immediately suggest a malignant process. This slow and subtle presentation is common in synovial sarcoma and often contributes to delays in diagnosis.

Imaging studies revealed a large mass centered in the parotid gland that displaced nearby structures without directly invading them. This pattern—pushing surrounding anatomy rather than destroying it—is a feature often seen in synovial sarcoma and can make the tumor appear less aggressive than it truly is.

Confirming the diagnosis

A surgical biopsy was performed to better understand the nature of the mass. Pathology revealed a tumor made up of both spindle-shaped cells and epithelial components, consistent with a biphasic synovial sarcoma. Additional testing using immunohistochemistry helped narrow the diagnosis, but definitive confirmation came through molecular testing.

As in most cases of synovial sarcoma, the tumor carried the characteristic chromosomal translocation known as t(X;18), involving the SS18 gene. Identifying this genetic alteration is considered the gold standard for confirming synovial sarcoma and is especially important in rare presentations where the diagnosis may not be immediately clear.

Treatment considerations in infants

Treatment strategies for synovial sarcoma differ based on age, tumor location, and extent of disease. In pediatric patients—particularly infants—care teams must balance aggressive cancer control with the long-term impact of treatment on growth and development.

In this case, the treatment plan included chemotherapy followed by surgical removal of the tumor. Complete resection was not possible due to the tumor’s close proximity to critical structures, including the internal carotid artery. Radiation therapy was avoided because of the high risk of long-term side effects in infants, including craniofacial growth disturbances and potential brain injury. Additional chemotherapy was used to help control residual disease, along with close imaging surveillance.

Why this case matters

Synovial sarcoma of the parotid gland is extremely rare, particularly in infants. This case underscores several important points for patients, families, and clinicians:

• Synovial sarcoma can occur outside the extremities, including the head and neck
  
• Tumors may appear slow-growing and deceptively benign at first
  
• Accurate diagnosis often requires specialized pathology and molecular testing
  
• Treatment in very young patients must be carefully tailored to reduce long-term harm
  

For families navigating a rare diagnosis, cases like this emphasize the importance of evaluation at experienced centers, multidisciplinary care, and persistence when something does not feel right.

Looking ahead

Although rare, pediatric synovial sarcoma continues to inform broader understanding of the disease. Each documented case contributes valuable insight into how synovial sarcoma behaves across different ages and anatomical locations. Ongoing research into the genetic drivers of synovial sarcoma may help guide future therapies that are both effective and less toxic—especially for children.

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