[54] Intraarticular Epithelioid Sarcoma (ES): Report of Two Cases, with Immunohistochemical and Molecular Cytogenetic INI-1 Study.

Kemal Kosemehmetoglu, Gulsah Kaygusuz, Armita Bahrami, Susana C Raimondi, Andrew L Folpe. Ankara Ataturk Education and Research Hospital, Turkey; Ankara University Ibn-i Sina Hospital, Turkey; St. Jude Children's Research Hospital, Memphis, TN; Mayo Clinic, Rochester, MN

Background: ES, a rare sarcoma with epithelial differentiation, most often occurs in the distal extremities but may occur in essentially any location. With the recent recognition that the loss of expression of the tumor-suppressor gene INI-1 may be associated with ES, it has become clear that ES may occur in previously unsuspected locations, such as bone. Here we report 2 cases of ES occurring within the knee.
Design: Two intra-articular cases coded as ES were retrieved from our archives. Both were immunopositive for cytokeratins (AE1/AE3 and OSCAR), CD34, vimentin, and epithelial membrane antigen, and both showed complete loss of expression of INI-1. Six cases coded as malignant pigmented villonodular synovitis (M-PVNS) were also retrieved and immunostained for the same markers using commercial antibodies and the Dako EnVision system. FISH was performed on formalin-fixed, paraffin-embedded sections by using a laboratory-developed dual-color probe containing INI1 [CTD-2511E13 + CTD-2034E7] (22q11.2) (OR) and PANX2 [RPCI3-402G11] (22q13.33) (GR) probe as control.
Results: Both cases of SE occurred in a clearly intra-articular location in the knee. Case 1 was that of a 60-year-old woman. Follow-up information available for this patient showed bilateral subpleural nodules that were radiographically consistent with metastases. Case 2 was that of a 19-year-old man with a long-standing history of pain and limited joint function. Morphologically, both tumors showed features of proximal-type ES with prominent rhabdoid morphology. Although immunohistochemistry of both tumors showed a complete loss of INI-1 protein, FISH analyses were negative for INI-1 gene deletion in both cases. The 6 cases of M-PVNS were negative for nearly all of the tested markers; INI-1 expression was retained.
Conclusions: Here we have reported, to the best of our knowledge, the first cases of intra-articular ES. The morphological and immunohistochemical features of this tumor are identical to those of ES in conventional locations, including loss of INI-1 expression. The loss of INI-1 protein expression in the absence of INI-1 gene deletion might distinguish proximal-type ES from malignant extrarenal rhabdoid tumor. Although we were not able to identify any additional cases of intra-articular ES within the 6 cases previously diagnosed as M-PVNS, intra-articular ES should be rigorously excluded before making the latter diagnosis.
Category: Bone & Soft Tissue

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 22, Tuesday Morning


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