Editor: Mahmut Akgul (

2022-35/September 12

Contributors: Fanni Santa, Levente Kuthi

A 52-year-old male patient presented with repeated gross hematuria and left-sided abdominal pain. Imaging studies revealed a 2.9 x 1.8 cm polypoid mass, within the calyces of the upper pole of the left kidney. CLICK ON THE BELOW THUMBNAILS TO ENLARGE PHOTOS.


a) Clear cell sarcoma

b) Synovial sarcoma, monophasic

c) Sarcomatoid carcinoma

d) Malignant rhabdoid tumor of the kidney

e) Renal hemangioblastoma

a) EWSR1::ATF1 fusion

b) EWSR1::FLI1 fusion

c) COL1A1:: PDGFB fusion

d) SS18::SSX1/2/4 fusion

e) Activating GNAS mutations

a) Chicken-wire vasculature

b) Prominent storiform pattern

c) Monomorphic spindle cell growth

d) CD34 expression

e) Benign course with no metastatic potential

1. b, 2. d, 3. c

Synovial sarcoma, monophasic

Synovial sarcomas (SS) are aggressive, infrequent categorizations of soft tissue sarcomas (STSs); accounting for 5 – 10% of all STSs. SS are commonly found in young adults and have a male predominance. It often arises in the deep soft tissue of extremities, particularly at juxta-articular locations. The median age of patients with primary renal SS is 40.5 (15–78) years. Flank/lumbar pain is the most commonly reported clinical presentation.

Histologically, SS is a monomorphic, spindle cell neoplasm that includes monophasic (spindle cell), biphasic, and poorly differentiated subtypes. Microscopically, monophasic SS displays solid sheet-like or fascicular growth patterns. These fascicles often intersect resembling a herringbone (fibrosarcoma-like) morphology. The tumor is hypercellular and strikingly monotonous with minimal pleomorphism. Cells are small with minimal cytoplasm and hyperchromatic nuclei. The tumor can have a syncytial appearance, as the cells lack distinct borders. HPC-like vasculature and wiry collagen bundles can be seen. Large and poorly differentiated tumors commonly have necrosis.

The immunophenotype, regardless of subtype, includes the expression of EMA, pankeratin, CK7, CK19, CD99, and TLE1, but typically lacks expression of desmin and CD34. Genetic analysis via FISH and RT-PCR can demonstrate the characteristic SYT18::SSX gene translocation and aids in the diagnostic process.

TLE1 is a sensitive marker for synovial sarcoma and is positive in approximately 90% of cases. However, TLE1 is positive in several tumors in the differential diagnosis, including solitary fibrous tumor, schwannomas, rhabdomyosarcoma, neurofibromas, and malignant peripheral nerve sheath tumors. Therefore, TLE1 lacks specificity, and a positive result should be followed up with testing for a t(X;18) (SS18::SSX1-2) translocation (TLE1 is sensitive, but not specific for synovial sarcoma). SS of the kidney is diagnostically challenging. Clinical information, morphology, IHC and genetic analysis are all essential to reach a correct pathological diagnosis.

1. El Chediak A, Mukherji D, Temraz S, Nassif S, Sinno S, Mahfouz R, Shamseddine A. Primary synovial sarcoma of the kidney: a case report of complete pathological response at a Lebanese tertiary care center. BMC Urol. 2018 May 11;18(1):40. doi: 10.1186/s12894-018-0358-z. PMID: 29751751; PMCID: PMC5948733.

2. Grampurohit VU, Myageri A, Rao RV. Primary renal synovial sarcoma. Urol Ann. 2011 May;3(2):110-3. doi: 10.4103/0974-7796.82182. PMID: 21747606; PMCID: PMC3130475.

Mohamed Maher, Breann Zeches, Shoujun Chen
Department of Pathology and Laboratory Medicine
East Carolina University/Vidant Medical Center
Greenville, NC


Renal tumor, synovial sarcoma