Synovial sarcoma of the kidney

Area of Science:

• Oncology
• Pathology
• Genetics

Background:

• Primary synovial sarcoma (SS) rarely originates in the renal parenchyma.
• Understanding the clinicopathologic features of rare renal tumors is crucial for diagnosis and management.

Purpose of the Study:

• To describe the clinicopathologic, immunohistochemical, and molecular characteristics of primary renal synovial sarcoma.
• To confirm the presence of the diagnostic SYT-SSX fusion gene in renal SS.
• To delineate the morphological spectrum and diagnostic markers for this rare entity.

Main Methods:

• Analysis of 7 cases of primary renal synovial sarcoma.
• Histopathological examination, including gross and microscopic features.
• Immunohistochemical staining for various markers (BCL-2, vimentin, MIC2/CD99, calponin, EMA, cytokeratin, CD34).
• Molecular analysis using reverse transcription-polymerase chain reaction (RT-PCR) to detect the SYT-SSX fusion gene.

Main Results:

• Seven patients (5 female, 2 male; age 15-46) presented with large solitary renal masses (10.0-17.0 cm).
• Histology showed monomorphic spindle cells with myxoid areas and a hemangiopericytomatous pattern; 4 cases had cysts lined by hobnailed cells.
• Immunohistochemistry revealed positivity for BCL-2, vimentin, and MIC2 (CD99). RT-PCR confirmed the SYT-SSX fusion gene in 4 cases.

Conclusions:

• Primary renal synovial sarcoma presents as a distinct entity with a specific morphological spectrum.
• Immunohistochemistry and molecular confirmation of the SYT-SSX fusion gene are essential for diagnosis.
• This rare renal tumor can have aggressive behavior, with two patients developing fatal pulmonary metastasis.