| Subtype / typical age | Defining tumor alteration | Useful IHC | Clinical behavior | Usual treatment framework |
|---|---|---|---|---|
| Adult renal leiomyosarcoma; typically older adults, median age about 62 y in national data | Usually complex-karyotype smooth-muscle sarcoma; no single pathognomonic renal-specific fusion established in gathered evidence | Smooth-muscle markers are typically used in practice; p16/p53 overexpression reported as potential prognostic indicators in review literature | Most common adult renal sarcoma histotype; often presents as a large renal mass and can be locally advanced or metastatic; among renal sarcoma histotypes, outcomes were relatively more favorable than angiosarcoma in 2024 registry analysis (pqac-00000002, pqac-00000003, pqac-00000004, pqac-00000008) | Complete surgical resection/nephrectomy is the mainstay; systemic therapy considered for advanced disease, with histology-tailored soft-tissue sarcoma regimens rather than renal-cell-carcinoma-specific therapy (pqac-00000004, pqac-00000005, pqac-00000006) |
| Renal synovial sarcoma; usually adolescents/young-to-middle-aged adults | **SS18::SSX** fusion (classically SS18-SSX1/2), causing BAF/chromatin-remodeling dysregulation; this is the defining lesion of synovial sarcoma generally (pqac-00000000) | TLE1, cytokeratin/EMA, CD99 may support diagnosis; SS18-SSX fusion-specific testing or molecular confirmation is preferred; diffuse SS18-SSX antibody staining is useful in modern practice for synovial sarcoma generally (pqac-00000000) | Rare primary renal spindle-cell sarcoma; can mimic other renal spindle tumors, so expert molecular pathology is important | Surgery with negative margins when localized; for advanced disease, treatment is generally extrapolated from synovial/soft-tissue sarcoma practice, with chemotherapy in selected patients (pqac-00000005, pqac-00000006) |
| Renal Ewing sarcoma / PNET; mainly children, adolescents, and young adults | **EWSR1::FLI1** or related Ewing-family fusion; defining molecular event of Ewing sarcoma family tumors (pqac-00000001, pqac-00000007) | CD99+, FLI1+, NKX2.2+ are useful supportive markers; molecular confirmation is required (pqac-00000007) | Aggressive renal presentation with high metastatic burden at diagnosis; pooled analysis found metastases at diagnosis in about 53% and nodal disease more frequent than in skeletal Ewing sarcoma (pqac-00000001, pqac-00000007) | Multimodal therapy: neoadjuvant/adjuvant **VDC/IE**-based chemotherapy, nephrectomy aiming for negative margins, and selective radiotherapy (pqac-00000001) |
| Pediatric clear cell sarcoma of kidney (CCSK); usually early childhood; distinct entity often confused with “kidney sarcoma” | **BCOR internal tandem duplication** is characteristic in many cases; **YWHAE::NUTM2** occurs in a subset; biologically distinct from adult primary renal sarcoma umbrella (pqac-00000000) | BCOR immunoreactivity is commonly used in practice; differential diagnosis requires molecular correlation because BCOR expression can occur in other sarcomas (pqac-00000000) | Pediatric malignant renal tumor distinct from adult renal sarcomas; included here because of naming confusion rather than because it is the same disease category | Pediatric renal-tumor protocols using surgery plus multiagent chemotherapy, with radiotherapy in selected cases; not managed as adult renal sarcoma (pqac-00000000) |
| Primary renal angiosarcoma; usually adults | No single defining recurrent renal-specific alteration established in gathered evidence; endothelial-lineage malignant vascular sarcoma | Endothelial markers are typically used in practice (for example CD31/CD34/ERG in angiosarcoma workups) | Very rare and aggressive; 2024 renal-sarcoma analysis found worse prognosis than leiomyosarcoma (HR 2.42) (pqac-00000004) | Surgery when feasible; systemic therapy for advanced disease is extrapolated from angiosarcoma/STS practice; radiation used infrequently overall in renal sarcoma cohorts (pqac-00000004, pqac-00000005) |
| Malignant rhabdoid tumor of kidney; predominantly infants/young children, but adult renal rhabdoid tumors were captured in registry data | Classically associated with **SMARCB1/INI1** loss in malignant rhabdoid tumors generally; renal-sarcoma registry identified this as one of the more common histotypes | INI1/SMARCB1 loss is the key diagnostic immunophenotypic finding in routine practice for rhabdoid tumors generally | Highly aggressive; one of the more common histotypes in the adult registry compilation despite overall rarity of adult cases (pqac-00000002, pqac-00000005) | Surgery is central when possible; multimodal pediatric or rhabdoid-tumor-directed systemic therapy is typically required, but renal-specific adult evidence is sparse (pqac-00000004, pqac-00000005) |
| Sclerosing epithelioid fibrosarcoma of kidney (SEF); very rare adults | **EWSR1::CREB3L1** fusion reported in renal SEF; molecularly distinctive fibroblastic sarcoma (pqac-00000009) | MUC4, vimentin, BCL2 positive; negative for S100, CD34, desmin in reported renal cases (pqac-00000009) | Exceptionally rare; at least one reported renal case had widespread metastases at diagnosis, indicating potentially aggressive behavior (pqac-00000009) | Complete excision when feasible; no renal-SEF-specific systemic standard established in gathered evidence (pqac-00000009) |


*Table: This table summarizes the major histologic entities that present as primary renal sarcoma or are commonly confused with it, highlighting subtype-defining molecular alterations, practical diagnostic markers, behavior, and treatment logic. It is useful for distinguishing the heterogeneous adult renal sarcoma umbrella from specific fusion-defined and pediatric renal tumor entities.*