Primary Synovial Sarcoma of the Kidney

Area of Science:

• Oncology
• Pathology
• Surgical Urology

Background:

• Renal tumors can present with varied imaging characteristics, sometimes mimicking benign conditions like angiomyolipoma (AML).
• Positron Emission Tomography Computed Tomography (PET-CT) can aid in differentiating benign from malignant renal masses, especially when Maximum Standardized Uptake Value (SUVmax) is elevated.
• Synovial sarcoma is a rare soft tissue malignancy, with limited reported cases originating in the kidney.

Observation:

• A 40-year-old female presented with right-sided abdominal pain and a 10 cm right kidney mass on CT scan.
• PET-CT revealed an elevated SUVmax of 7.8, raising suspicion for malignancy despite initial consideration of AML.
• Surgical resection via transperitoneal right radial nephrectomy was performed due to suspected malignancy, revealing tumor adhesion to the duodenum and inferior vena cava.

Findings:

• Histopathological examination confirmed a synovial sarcoma, characterized by gland-like/cyst-like structures and solid growth of fusiform and oval basophilic cells.
• The tumor occupied a significant portion of the excised kidney, with surrounding cyst-like changes and brittle, grayish tissue.
• No malignant findings were noted in the adrenal gland.

Implications:

• This case underscores the importance of considering rare renal malignancies, such as synovial sarcoma, in the differential diagnosis of large kidney tumors with high metabolic activity on PET-CT.
• Accurate diagnosis requires thorough histopathological evaluation, especially when imaging findings are ambiguous.
• Reporting such rare cases contributes valuable data to the limited global understanding of renal synovial sarcomas, aiding future diagnostic and treatment strategies.