Epithelioid Sarcoma

Epidemiology:

• Age range 4-90y
• History of trauma (25%)

Common sites:

• Hand
• Distal arm
• Leg
• Lymph node mets are more common than in other sarcomas

Gross features:

• May be clinically distinct raised nodules with central ulceration
• Subcutaneous/dermal or deep seated
• Gray-white cut surface
• Well-circumscribed or infiltrating
• Necrosis
• hemorrhage
• Spreads proximally up the extremity with numerous cutaneous nodules and ulcerative lesions
• Grows along tissue planes

Histologic features:

• nodular
• Central necrosis, hemorrhage, calcification
• Mixture of plump spindled and epithelioid rounded/polygonal eosinophilic cells, merging imperceptibly
• Mild to moderate pleomorphism
• Nuclei round to slightly irregular ovoid
• Irregularly distributed, vesicular chromatin
• Conspicuous nucleolus
• Eosinophilic cytoplasm
• Fairly well defined cell borders
• Multinucleated cells sometimes
• Rhabdoid cells maybe
• Inflammatory infiltrate at periphery frequently
• Lymphocytes
• Plasma cells
• Areas of fibrosis and hyalinization may occur
• Fibroma-like variant
• Only interspersed epithelioid cells

Immunophenotype:

Marker:	Sensitivity:	Specificity:
INI-1 (SMARCB1) (neg)	Both types of ES
CK8	94%
34-beta-EH12 high-molecular weight keratin	50%
CK5/6 (neg)
EMA	50-96%
CD34	>50%
CD31 (neg)
vimentin
CEA (focally)
Desmin	Maybe (rhabdoid component)
S100 (neg)

Molecular features:

• 22q11 implicated in particular (SMARCB1) (hSNF5, INI-1) (also implicated in pediatric rhabdoid tumours of the kidney, extrarenal, and CNS among others)
• Mutation, deletions, and other alterations
• 8q gains frequently
• i(8)(q10)
• Complex

Other features:

• Rare
• Tend to recur locally and metastasize over long-term
• Some have characteristic clinical appearance of prominent nodules raised above the skin surface with central ulceration, occurring in a line from the wrist to the elbow.
• EM:
• Spectrum / range of differentiation

References:

• WHO blue book (2013)
• IHC and genetics sections only
• Sternberg 2004
• Silverberg SG, DeLellis RA, Frable WJ, LiVolsi VA, Wick MR. Silverberg's Principles and Practice of Surgical Pathology and Cytopathology: 2-Volume Set. 4th ed. Churchill Livingstone; 2005.