Turkish Journal of Pathology

Türk Patoloji Dergisi

Turkish Journal of Pathology

Turkish Journal of Pathology

2012, Vol 28, Num, 3     (Pages: 270-273)

A Case of Cd20 Positive Mediastinal Rhabdomyosarcoma

Gülden DİNİZ 1, Ferah GENEL 2, Nur YÜCEL 3, Ayşen TÜREDİ 2, Canan VERGİN 2

1 Department of Dr. Behçet Uz Children's Hospital,Pediatrics, İZMİR, TURKEY
2 Dr. Behçet Uz Çocuk Hastanesi, Pediatri Bölümü, İZMİR, TÜRKİYE
3 Dr. Suat Seren Chest Diseases Hospital, Department of Pathology, İZMİR, TURKEY

DOI: 10.5146/tjpath.2012.01135
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We present the case of a 16-year-old boy admitted with a large mediastinal mass. Both in the mediastinal tru-cut biopsy and the bone marrow biopsy, a malignant small round cell tumor was determined. The clinical diagnosis was leukemia or lymphoma. The cytoplasmic CD20 expression was shown on the tumor cells of the mediastinal tru-cut biopsy. Rhabdomyosarcoma was diagnosed by the flow cytometric analysis and immunohistochemical demonstration of muscle markers.

Rhabdomyosarcomas are traditionally distinguished from lymphomas by their absence of lymphoid markers such as CD20. But in this case we have encountered CD20 expression in the tumor cells. This finding lead us to conclude that the presence of a lymphoid phenotype does not absolutely exclude the diagnosis of rhabdomyosarcoma.

Keywords : Rhabdomyosarcoma, CD20 Antigen, Flow cytometry, Differential diagnosis