[65] Clinicopathological Spectrum of 14 Myoepithelial Tumors, Primarily Involving Soft Tissues, Including Immunohistochemical Profile and EWSR1 Rearrangement in a Subset of Cases

Bharat Rekhi, Mukund Sable, Nirmala A Jambhekar. Tata Memoral Hospital, Mumbai, Maharashtra, India

Background: Primary soft tissue myoepithelial tumors (METs) are rare. Recent studies have shown EWSR1 rearrangement in certain METs.
Design: Herein, clinicopathological features of 14 primary soft tissue METs, included after critical review, are presented with EWSR1 results.
Results: Fourteen tumors occurred in 12 men and 2 women within age-range of 18-60 years (mean 39.2) in upper extremities (4)(28.5%), chest wall 3(21.4%), paravertebral region 3(21.4%), pelvis 2(14.2%) and lower extremities (2)(14.2%). Tumor size varied from 2-21.6 cm (mean 8.7). Microscopically, most tumors were at least focally circumscribed, including 5 benign and 9 malignant types. Various patterns, cells and matrix-types were noted, commonest being cord-like and diffuse arrangement of polygonal cells in a myxoid matrix, un-associated with duct formations. By IHC, tumors were positive for EMA (10/12)(83.3%), CK/MNF116(3/12)(25%), p63(7/10)(70%), CD10(4/6)(66.6%), calponin (6/6)(100%), S-100P(11/13)(84.6%), GFAP (6/12)(50%), SMA(3/9)(33.3%), vimentin(4/4)(100%), INI1/SMARCB1(6/10)(60%), brachyury(0/11) and CD34(0/5), including 92.8% positivity for an epithelial marker. EWSR1 gene rearrangement was detected in 3/6 (50%) METs (1 benign, 2 malignant); in an eccrine porocarcinoma (AE1/AE3+,EMA+,CEA+,p63+,CK5/6+) and was absent in a myxoid-type epithelioid sarcoma (CK+,EMA+,CD34+,vimentin+) that formed close differentials.

All 11 patients with known treatment details underwent tumor resection. Three tumors (2 malignant, 1 benign) resected with unknown marginal status recurred; 2 patients died and a single patient with myoepithelial carcinoma, who underwent wide-excision, is disease-free.
Conclusions: This study testifies a wide spectrum of soft tissue METs, including benign and malignant subtypes that are best treated with wide-excision. EMA and S-100P are optimal markers in our settings that should be supplemented with AE1/AE3, p63, GFAP and calponin in certain cases. Morphological features must be correlated with IHC results. Brachyury is useful in separating parachordoma/myoepithelioma from chordoma. Certain METs are INI1-deficient. EWSR1 rearrangement mostly occurs in deep-seated METs, irrespective of benign or malignant types.
Category: Bone & Soft Tissue

Monday, March 4, 2013 1:00 PM

Poster Session II # 11, Monday Afternoon


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