RESIDENT CASE STUDIES

Week 11 June 28 - July 4, 2003: Case 1   

Table of Contents | List of Diagnoses | Case 1 | Case 2 | Case 3

32 year old male with right knee mass that is negative for actin, desmin, and Myo D1 with no SSX/SSY translocation

Discussion 
Epithelioid sarcoma (ES) is a distinct tumor of unknown lineage affecting mainly adolescents and young adults. It is rare in infants and the elderly. It may be misdiagnosed as a benign lesion especially benign granulomatous process.¹ The most commonly affected areas are the flexor surface of fingers, hand, wrist and forearm. It may be superficial or deep-seated. The trunk, head and neck regions are seldom involved by classical epithelioid sarcoma.¹ When superficial it usually presents as firm, slow growing, painless solitary or multiple nodules/plaque-like lesions. There may be ulceration of the skin. Deep-seated lesions are often attached to tendons, tendon or aponeurosis.¹ The size may range from a few millimeters to several centimeters, (especially in deep seated tumors). 

Histologically, the classic ES shows a characteristic nodular growth pattern frequently (but not always) with central necrosis (geographic necrosis), simulating benign necrobiotic processes such as rheumatoid nodule and granuloma annulare. The typical nodule is composed of a mixed proliferation of eosinophilic epithelioid and spindle cells with nuclear atypia, vesicular nuclei and small nucleoli.¹ The number of mitoses is usually low--often less than 5/hpf. The cells can have rhabdoid features.¹ ES is characteristically immunoreactive for vimentin and epithelial markers (e.g. LMK, HMK, EMA, CK8 and CK19).^1,2 Half of the cases are reported positive for CD34,² and occasional reactivity for muscle specific actins, NSE and S100 have been reported.² 

ES is an aggressive sarcoma with high recurrence rate³ with an overall recurrence rate of 80% at 10 years.⁴ 

Adverse prognostic factors in ES include male sex, advanced age at diagnosis, large tumor size (>5cm), deep location, nuclear pleomorphism, high mitotic activity, presence of vascular and or nerve invasion, multiple recurrence, presence of lymph node metastasis at diagnosis.¹

References:

¹Fletcher CDM, Unni KK, Mertens F. (Eds.): World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of Soft Tissue and Bone. IARC Press: Lyon 2002.

²Miettinen M, Fanburg-Smith JC, Virolainen M, et al. Epithelioid sarcoma: an immunohistochemical analysis of 112 classical and variant cases and a discussion of the differential diagnosis. Hum Pathol 1999;30:934-942.

³Halling AC, Wollan PC, Pritchard DJ, et al. Epithelioid sarcoma: a clinicopathologic review of 55 cases. Mayo Clin Proc 1996;71:636-642.

⁴Chase DR. Do “rhabdoid features“ impart a poorer prognosis to proximal-type epithelioid sarcoma? Adv Ana Pathol 1997;4:293-299.