Metastatic small round blue cell tumor. A genetic puzzle.
Khemasuwan D, Abrencillo R, Ormsby A, DiGiovine B, and Diaz-Mendoza J. Metastatic small round blue cell tumor. A genetic puzzle. Am J Respir Crit Care Med 2015; 191.
Am J Respir Crit Care Med
Small round blue cell tumor represents a group of the aggressive solid tumors which are mostly found in pediatric and young adolescent population. Case presentation: A 26 year old male with history of enlarging right groin mass for several months with no recent work up who presented with progressively worsening shortness of breath over the past two weeks. CT chest revealed mediastinal lymphadenopathy with diffuse pulmonary nodules and septal thickening throughout both lungs. Patient developed spontaneous pneumothorax of left lung which was managed by 28 Fr chest tube placement. Bronchoscopy was performed which revealed diffuse whitish nodules throughout endobronchial mucosa (Figure1). Endobronchial biopsy showed small round blue cell tumor (SRBCT). The biopsy of right groin mass also confirmed the diagnosis of SRBCT. Immunohistochemical staining was positive for CAM 5.2 and Desmin, but negative for CD56 and leukocyte common antigen. RT-PCR for EWS-Fli1 and EWS-ERG were negative. Break apart FISH for EWSR1 was positive. Follow-up PCR was positive for Ewing sarcoma gene (EWS) and Wilms' tumor gene (WT1) rearrangement, indicating presence of t(11;22)(p13;q12). These findings are consistent with desmoplastic small round cell tumor (DSRCT). Patient received the first round chemotherapy regimen with vincristine, cyclophosphamide, and doxorubicin. Discussion: Malignant small round blue cell tumors (SRBCT) is a group of morphologically similar rare tumors that include: Ewing sarcoma family of tumors (EFT), peripheral primitive neuroectodermal tumor (PNET), small cell osteosarcoma, mesenchymal chondrosarcoma and DRSCT among others. Therefore, accurate sub-typing is essential because therapeutic options and prognoses very widely depending on the diagnosis. These cancers are difficult to distinguish by light microscopy, and currently no single test can precisely distinguish these cancers. To confirm the diagnosis, pathologists rely on several techniques, including immunohistochemistry, cytogenetics, interphase fluorescence in situ hybridization, and reverse transcription-polymerase chain reaction (RT-PCR). The presence of the specific cytogenetic abnormality t(11;22)(p13;q12) involving EWS- WT1 fusion confirms the diagnosis. The prognosis of DSRCT remains very poor with 5-year survival rate of 15%. The treatment with intense alkylator therapy (P6 protocol), and gross total resection and external beam radiotherapy seemed to improve overall survival. (Figure Presented).