Primary Subcutaneous Primitive Neuroectodermal Tumor with Aggressive Behavior and an Unusual Karyotype: Case Report

Byline: Gino R. Somers (1), Mary Shago (2), Maria Zielenska (2), Helen S.L. Chan (3), Bo Y. Ngan (1) Keywords: subcutaneous primitive neuroectodermal tumor; electron microscopy; immunohistochemistry; karyotype; metastases; reverse transcriptase polymerase chain reaction Abstract: Primitive neuroectodermal tumor/Ewing sarcoma (PNET/ES) rarely occurs in the skin and subcutaneous tissues. We present a case of a 16-year-old girl with primary cutaneous and subcutaneous PNET/ES of the abdominal wall. Despite wide local excision and chemotherapy, she rapidly developed cranial bone and brain metastases, followed by lung and skeletal metastases, and died shortly thereafter. The recurrent tumor exhibited light microscopic features of a small, round, blue cell tumor with intracytoplasmic glycogen. Immunohistochemical analysis showed positivity for CD99, CD56, S100, and glial fibrillary acid protein, and ultrastructural features included cytoplasmic glycogen and focal complex interdigitating synaptic junction-like cytoplasmic folds. Cytogenetic analysis of the relapsed tumor showed a complex karyotype: 47,XX,i(1)(q10), der(4)t(4 19) (q33[proportional to]q35 q13.1), + 8,t(15 17)(q24 p11.2[proportional to]p12),der(19)t (19 20)(q13.1 p11.2),der(22)t(20 22)(q13 q13). Cytogenetic, interphase fluorescence in situ hybridization, and molecular genetic analyses failed to show t(11:22) (q24 q12) or abnormalities of chromosome region 22q12. The clinical behavior and atypical and complex cytogenetic abnormalities exhibited by the tumor in this patient are unusual and represent the most aggressive end of the clinical spectrum of cutaneous and subcutaneous PNET/ES. Author Affiliation: (1) Division of Pathology, Department of Paediatric Laboratory Medicine, Hospital for Sick Children, Toronto, ON, M5G 1X8, Canada (2) Division of Molecular Genetics, Department of Paediatric Laboratory Medicine, Hospital for Sick Children, Toronto, ON, M5G 1X8, Canada (3) Division of Haematology/Oncology, Department of Paediatrics, Hospital for Sick Children, Toronto, ON, M5G 1X8, Canada Article History: Registration Date: 01/01/2004 Received Date: 18/02/2004 Accepted Date: 17/05/2004 Online Date: 06/10/2004