Qap (Anatomical Pathology) 

QAP Peer Review

AP186
Case History: M/20 Left pelvic pain with rest and nocturnal pain. Mixed sclerotic and lytic lesion in left ileum. Biopsy done.
Intended diagnosis: Ewing's sarcoma. Contributed by:JKCC
Code Diagnosis Comment Score
anonymous Malignant small round cell tumour, consistent with osteosarcoma, small cell type (70%). Differential diagnosis are other small round cell tumours, such as PNET/Ewing's sarcoma, rhabdomyosarcoma. (30%) Immunostains to exclude other small round cell tumour, including CD99, LCA, desmin, myoglobin, myogenin, neural markers like synaptophysin, chromogranin.  80
anonymous Small cell osteosarcoma nil  50
anonymous Small round cell tumor, favouring Ewing's sarcoma. DDx small cell osteosarcoma. Ewing's sarcoma can be confirmed by positive staining for CD99, osteosarcoma should not be stained.  100
anonymous Ewing's sarcoma immunostaining for CD99 (+)  100
anonymous Small cell osteosarcoma. 100% nil  50
anonymous Malignant small round cell tumor, consistent with Ewing's sarcoma. (100%) Do CD99 stain to confirm. Other stains to exclude other DDx e.g. myogenin to exclude rhabdomyosarcoma; LCA and Tdt to exclude lymphoma.  100
anonymous Malignant small round cell tumor, consistent with Ewing's sarcoma. (100%) Do CD99 stain to confirm.  100
anonymous Ilium bone tumour - small round cell tumour with DDX (total 100%) 1.Ewing sarcoma 2.Alveolar rhabdomyosarcoma 3.Small cell osteosarcoma 4.Malignant lymphoma 5.PNET Need to perform the panel of immunomarkers, glycogen stains, and if necessary, ultrastructural studies for reaching diagnosis.  80
anonymous Malignant small round cell tumour (100%) Take more blocks for morphological study: look for lipomatous, osteoid and rhabdomyoblastic differentiations. Perform immunohistochemical stains : epithelial markers (for metastatic carcinoma, eg renal cell carcinoma), LCA (for lymphoid malignancy), S100(for neurological differentiation and lipomatous ), SMA, desmin, myoD1 etc (for smooth and skeletal muscle differentiation), CD99 (for Ewing's/Primitive neuroectodermal tumours).  80
anonymous Ewing sarcoma VS Osteosarcoma, small cell type. Immuno stain and special stain studies are needed.  75
anonymous small round cell tumor favors EWING'S SARCOMA (100%) nil  100
anonymous Ewing's sarcoma/PNET 100% PAS+/-D for glycogen CD99 should be positive Desmin, MyoD1 should be negative (exclude rhabdomyosarcoma) t(11;22) cytogenetics or RT-PCR for EWS/FLI1 to confirm  100
anonymous Small cell osteogenic sarcoma nil  50
anonymous Ewing's sarcoma nil  100
anonymous Small round cell tumour. DDx: Ewing sarcoma, small cell osteosarcoma Do CD99, correlate with XRay. Probability: 100% nil  80
anonymous Small round cell tumour (100%), favour Ewing's sarcoma (80%), small cell osteosarcoma (20%). Correlate with radiological findings. Perform PAS with and without diastase and CD99 immunostain to confirm Ewing's sarcoma; small cell osteosarcoma is mostly negative for CD99.  100
anonymous Ewing sarcoma (70%) small cell osteosarcoma (30%) Further blocks to demonstrate osteoid formation and molecular study for t(11;22) for definite diagnosis. Immunohistochemical staining for CD99, LCA, desmin to exclude other differential diagnoses of small round cell tumour.  100