Introduction When answering questions with regard to orthopaedic pathology it is very useful to have an understanding of the different differential groups. This topic is broken down into the following differentials by Age Location Imaging Tumor Grade Histology Treatment Differentials by Age Age Benign Malignant Infants and childres(0 to 5 years) Osteomyelitis Osteofibrous dysplasia Metastatic rhabdomyosarcoma Metastatic rneuroblastoma Leukemia Young patient (10-40 years) NOFOsteoid osteomaGiant cell tumorABCUBCOsteochondroma & MHEChondroblastomaFibrous dysplasiaOsteomyelitisEosinophillic granuloma Osteosarcoma Ewing's Desmoplastic fibroma Leukemia Lymphoma Older patient (40-80 years) EnchondromaBone infarctBone islandPaget's diseaseHyperparathyroidism Metastatic bone disease Myeloma Lyphoma Chondrosarcoma MFH Secondary sarcoma (Paget's, irradiation) Differential by Location Location in Bone Multiple lesions in Young Patient EGFibrous dysplasiaLeukemiaLymphomaHemangioendotheliomaEnchondroma / Olliers / Marfucci'sOsteochondroma / MHENOF / Jaffe-Campanacci syndrome Multiple lesions in Older Patient Paget'sMetastatic bone diseaseMultiple myelomaLymphoma HyperparathyroidismBone infarcts Epiphyseal / Subchondral Lesions ChondroblastomaGiant cell tumorClear cell chondrosarcoma Surface Lesions Osteochondroma / MHE Parosteal osteosarcomaPeriosteal osteosarcoma Periosteal chondroma Post Traumatic Surface Lesions Florid reactive periostitisBPOPTurret exostosisSubungal exostosis Location in Body Sacrum in young patients (10-40) Giant cell tumorABCEwing'sOsteosarcoma Sacrum in older patients (40-80) ChordomaMetastasisMyelomaLymphomaChondrosarcomaMFH Tibial lesions AdamantinomaOsteofibrous dysplasiaFibrous dysplasiaOsteomyelitis Hand and Foot Intramedullary destructive lesions EnchondromaGiant cell tumorABCGiant cell reparative granuloma Metastatic carcinoma (only in older patients) Imaging Differential Radiographs "Bubbly" lesion on xray NOFABCUBC Bone scan is cold Multiple myelomaMelanoma Well defined "punched out" lesion Eosinophillic granuloma Giant Cell Tumor Multiple myeloma Differential by Grade ORIGIN BENIGN LOW GRADE HIGH GRADE Bone tumors Osteogenic Osteoid osteomaOsteoblastoma Parosteal osteosarcoma • Periosteal osteosarcoma • Intramedullary osteosarcoma Chondrogenic EnchondromaOsteochondromaChondroblastomaChondromyoid fibroma Chondrosarcoma Dedifferentiated chondrosarcoma Unknown origin • Giant cell tumor• Histiocytoma • Adamantinoma • Ewing's tumor Fibrogenic • Nonossifying fibroma • Desmoplastic fibroma • Fibrosarcoma Hematopoietic • Multiple myeloma• Lymphoma• Leukemia Vascular • Hemangioma • Hemangioendothelioma Notochordal • Chordoma Lipogenic • Lipoma Soft tissue tumors Synovial • Giant cell tumor of tendon sheath x • Synovial sarcoma• Malignant giant cell tumor of tendon sheath Fibrogenic & Fibrohistiocytic • Fibroma• Fasciitis (nodular or proliferative) • Fibrous histiocytoma x • Fibrosarcoma• Myxofibrosarcoma• Malignant fibrous histiocytoma Lipogenic • Lipoma • Myxoid liposarcoma • Pleomorphic liposarcoma Muscle tissue • Leiomyoma• Rhabdomyoma x • Leiomyosarcoma• Rhabdomyosarcoma Vascular • Hemangioma• Lymphangioma• Glomus tumor x • Lymphangiosarcoma• Hemangiosarcoma Neurogenic • Neuroma (traumatic or Morton's)• Neurilemoma (benign schwannoma)• Neurofibroma (neurofibromatosis) x • Malignant schwanoma• PNET tumors Differential by Histology Histology Bone marrow aspiration and biospy required for diagnosis and staging • Lymphoma• Ewings Small round cell tumor • Lymphoma• Leukemia• Ewing's sarcoma• Metastatic carcinoma (small cell lung) • Rhabdomyosarcoma• Neuroblastoma Epithelial Glands seen on histology • Synovial sarcoma (biphasic)• Metastatic carcinoma• Glomus tumor Bimorphic histology • Dedifferentiated chondrosarcoma• Synovial sarcoma• Osteosarcoma with chondroblastic features Multi-nucleated Giant cells present • Giant cell tumor• Chondroblastoma• Aneurysmal bone cyst Hemosiderin pigmentation • NOF• PVNS• UBC Immunostains Leukocyte common antigen • Lymphoma CD138 • Myeloma CD99 • Ewing's CD1A • EG CD31 and 34 • DFSP• Angiosarcoma CD20 and CD45 (B cell) • Lymphoma S100 • EG• Chordoma • Chondroblastoma • Melanoma • Clear cell sarcoma• Nerve sheath tumors (Schwanoma) • Ewing's• Synovial Sarcoma Elastin • Elastofibroma Keratin • Metastatic bone disease• Synovial sarcoma• Chordoma• Epitheloid sarcoma• Adamantinoma Factor VIII • Angiosarcoma Smooth muscle actin • Leiomyosarcoma Desmin • Rhabdomyosarcoma Myoglobin • Rhabdomyosarcoma CK7 • Breast CA• Lung CA CK125 • Ovarian CA CK20 • Colon CA TTF1 • Lung CA Vimentin • Synovial sarcoma • Rhabodymosarcoma • Leiomyosarcoma • Ewing Sarcoma EMA • Synovial sarcoma Differential by Treatment NonOperative Observation (if asymptomatic) Fibrous dysplasia / osteofibrous dysplasia Enchondromas / Olliers / Marfucci's Osteochondroma /MHENOF / Jaffe-CampanacciPaget'sEosinophillic GranulomaLipoma (soft tissue) Bisphosphonate therapy Metastatic bone disease (with wide resection and radiation) Myeloma (with chemotherapy) Paget's disease (with observation) Fibrous dysplasia (with observation) Radiation alone Solitary myeloma Chemotherapy alone LyphomaMultiple myeloma Operative Radiofrequency ablation Osteoid osteoma Aspiration and Injection UBC Curretage and Bone Grafting GCTABC ChondroblastomaChondromyxoid fibromaOsteoblastomaNOF(if symptomatic) Marginal Resection Periosteal chondromaNeurilemoma (soft tissue) Nodular fasciitis (soft tissue) Epidermal inclusion cystGlomus tumor Wide Resection Alone • Chondrosarcoma• Parosteal osteosarcoma• Chordoma• Adamantinoma• Squamous cell (if no mets) Wide Resection + Irradiation • Metastatic Bone Disease • Soft tissue sarcoma-high grade (angiosarcoma, synovial sarcoma, liposarcoma, desmoid tumor, MFH/fibrosarcoma) Wide Resection + Chemotherapy • Osteosarcoma• Periosteal osteosarcoma• Ewing's• MFH / fibrosarcoma • Secondary sarcoma• Dedifferentiated chondrosarcoma• Rhabdomyosarcoma (exception to soft tissue sarcoma tx)