Lytic Bone Lesions

Bone tumors are mostly benign. The most important determinants in imaging of bone tumors are morphology on plain radiograph (well-defined lytic, ill-defined lytic, and sclerotic lesions) and age of the patient at presentation. Well-defined osteolytic bone tumors and tumor-like lesions have many differentials in different age groups. For simplicity, a widely used mnemonic for lytic bone lesions is extremely helpful: FEGNOMASHIC. We have attempted to describe the most characteristic features of each of these tumors. The different bone tumors and lesions discussed are as follows: fibrous dysplasia (FD), eosinophilic granuloma (EG), enchondroma, giant cell tumor (GCT), non-ossifying fibroma, osteoblastoma, aneurysmal bone cyst (ABC), solitary bone cyst (SBC), hyperparathyroidism (Brown tumor), infection (always kept in differential diagnosis while dealing with bone lesions), chondroblastoma, CMF, metastasis, myeloma (any bone lesion detected in 40 years and older, must be ruled out for metastasis and myeloma). The normal variant that can mimic lytic bone lesions is pseudocyst; this is an area of focal trabecular rarefaction at a low-stress region. Pseudocysts most commonly occur in the greater tuberosity of the humerus, calcaneus, and radial tuberosity. An osteolytic lesion with an ill-defined zone of transition is generally typical of malignant bone tumors (Ewing sarcoma, osteosarcoma, metastasis, leukemia) and aggressive benign lesions (giant cell tumor, infection, eosinophilic granuloma).