D.D. OF solitary osteolytic bone lesion.

Differential diagnosis of osteolytic bone lesion

Narrowing the likely diagnosis of a solitary lucent bone lesion is based on six steps.

Step 1 is to consider the most likely possibilities, represented by the mnemonic "FOG MACHINES":

Fibrous Dysplasia
Osteoblastoma
Giant Cell Tumor
Metastasis / Myeloma
Aneurysmal Bone Cyst
Chondroblastoma / Chondromyxoid Fibroma
Hyperparathyroidism (brown tumors) / Hemangioma
Infection
Non-ossifying Fibroma
Eosinophilic Granuloma / Enchondroma
Solitary Bone Cyst

Step 2 focuses on the patient’s age. According to Edeiken, 80% of malignant tumors can be correctly diagnosed on the basis of age alone. For a solitary lucent bone lesion, the most likely diagnoses by age include:
Under age 10: neuroblastoma (infants) and Ewing’s sarcoma of tubular bones
Age 10-30: osteosarcoma and Ewing’s sarcoma of flat bones
Age 30-40: reticulum cell sarcoma, fibrosarcoma, parosteal osteosarcoma, malignant giant cell tumor, and lymphoma
Over age 40: metastatic carcinoma, multiple myeloma, and chondrosarcoma

Step 3 is to determine how aggressive the lesion is. The continuum begins with a normal bone appearance in a non-aggressive lesion. The insidious nature is assumed to increase through the following:
Geographic, narrow zone of transition and sclerotic margin
Geographic, narrow zone of transition (without a visible margin)
Geographic, wide zone of transition
Moth-eaten appearance
Permeative appearance

Step 4 focuses on the matrix. Most lesions do not produce a matrix and thus appear radiolucent. A chondroid matrix, characterized by a "rings and arcs" appearance, is typical in enchondroma, chondrosarcoma, chondromyxoid fibroma, and other cartilage-based tumors. An osteoid matrix, typically described as "cloud-like", is a common feature of osteoma, osteoblastoma, bone island, and osteosarcoma.

Step 5 considers the periosteal reaction. Periosteal reaction varies widely and represents involvement of the outer cortical rim by the tumor. Its appearance can also be described by a continuum from non-aggressive to very aggressive. Solid periosteal reaction, the least aggressive type, can be caused by infection, benign neoplasms like osteoid osteoma and eosinophilic granuloma, hypertrophic pulmonary osteoarthropathy, or deep venous thrombosis (in the lower extremity). More aggressive reactions, including lamellated, "hair-on-end" or sunburst appearances, or Codman’s triangle, can be caused by osteomyelitis or malignant neoplasms, such as osteosarcoma, chondrosarcoma, fibrosarcoma, lymphoma, leukemia, and metastasis.

In the final step, the location within the bone is taken into account. Chondroblastoma and osteomyelitis typically arise in the epiphysis. The metaphysis is the most likely location for a primary neoplasm other than chondroblastoma, including all other entities recalled by the "FOG MACHINES" mnemonic. Similarly, all FOG MACHINES entities except chondroblastoma, giant cell tumor, and osteoblastoma may arise in the diaphysis.

By careful examination of the features of the lesion you can categorize the lesion as aggressive or non-aggressive. These features, considered within the context of the patient’s demographics and the location of the lesion, allow a reasonable differential diagnosis prior to biopsy and will serve as a guide to planning surgical management.