Epithelioid sarcoma (ES)
- First described by Enzinger in 1970
- Uncommon, accounts for 5 - 8% of malignant non-RMS in children
- Most prevalent in young adults ages 20 – 40 years. Rarely found in children
- Generally presents in fascial planes, aponeuroses, and tendon sheaths of the extremities, particularly in the hand (the ﬁngers) and foot.
- Associated with a risk of spread to regional lymph nodes
Two types - classic ES and proximal-type ES share a similar immunophenotypic proﬁle
- Distinctive nodular, granuloma-like pattern, with spindle and epithelioid cells circumscribing areas of central degeneration and necrosis.
- Rare subtype associated with more aggressive behavior and worse
- Usually deep-seated soft tissue mass at proximal body sites
- Sheets of large, atypical, epithelioid cells with vesicular nuclei and prominent nucleoli, with a rhabdoid phenotype.
- Alterations of chromosome 22 with deletions of the SMARCB1/INI1 gene were recently described in this variant
- 5-year event-free survival (EFS): just over 60%
- 5 year overall survival (OS): just over 90%
- OS rate dropped to 86.9% at 10 years
- OS rate at 15 years was 72.4%
Local disease recurrence was the major cause of treatment failure.
Most signiﬁcant ﬁnding inﬂuencing both EFS and OS was tumor site, with a tumor location in the extremities predicting a favorable outcome