Clin Med: Neoplasms, Malignancy, Osteoporosis

Paget Disease of Bone

A chronic bone disorder characterized by increased osteoclast-mediated bone resorption followed by compensatory osteoblast activity, resulting in enlarged, weak, and disorganized bone.

Fibrous Dysplasia

A benign developmental bone disorder caused by a postzygotic genetic mutation in which normal bone is replaced by fibrous tissue and immature woven bone.

McCune-Albright Syndrome

A condition defined by the triad of polyostotic fibrous dysplasia, café-au-lait skin macules, and autonomous endocrine hyperfunction, such as precocious puberty.

Shepherd's Crook Deformity

A characteristic structural deformity of the proximal femur visible on radiographs in patients with fibrous dysplasia.

Ground-Glass Appearance

A classic radiographic finding in fibrous dysplasia where the lesion demonstrates a homogeneous, hazy opacity on X-ray.

Soft-Tissue Sarcoma

A rare group of malignant tumors arising from mesenchymal tissues (such as muscle, fat, fibrous tissue, blood vessels, or peripheral nerves) that most commonly present as a deep, firm, or enlarging mass in the extremities.

Giant Cell Tumor of Bone

An intermediate, locally aggressive primary bone tumor that can recur locally and rarely metastasize to the lungs.

Osteosarcoma

The most common primary malignant bone sarcoma in children and adolescents, typically arising in the metaphysis of long bones around the knee and presenting as a mixed lytic and sclerotic lesion.

Sunburst Appearance

An aggressive periosteal reaction seen on radiographs in osteosarcoma, caused by rapid tumor growth pushing thin bony spicules outward perpendicular to the cortex.

Codman Triangle

A radiographic feature created when a rapidly growing tumor lifts the periosteum off the cortical bone, forming a triangular elevation at the tumor margin.

Ewing Sarcoma

An aggressive primary bone sarcoma primarily affecting children and adolescents (peak age 10–20 years), typically arising in the pelvis or diaphysis of long bones and often presenting with localized pain, swelling, and systemic symptoms.

Onion-Skin Periosteal Reaction

A classic radiographic finding in Ewing sarcoma characterized by multi-layered, laminated periosteal bone formation in response to tumor invasion.

Chondrosarcoma

A malignant cartilage-producing bone tumor that primarily affects middle-aged and older adults, commonly arising in the pelvis, femur, or shoulder girdle and characteristically resistant to standard chemotherapy and radiation.

Rings-and-Arcs Calcification

A characteristic chondroid matrix calcification pattern visible on radiographs in cartilage-forming bone lesions such as chondrosarcomas.

Metastatic Bone Tumors

Malignant neoplasms that spread to bone via the bloodstream from primary carcinomas elsewhere (most commonly breast, prostate, lung, kidney, and thyroid), representing the most common type of malignant bone tumor.

Osteolytic vs Osteoblastic (Blastic) Metastases

Radiographic patterns of metastatic bone destruction or formation, one version of lesions (common in renal, thyroid, and lung cancers) break down bone, whereas the other lesions (classic for prostate cancer) cause dense bone deposition.

Metastatic Spinal Cord Compression

An oncologic emergency caused by spinal bone metastases impinging on the spinal cord or cauda equina, presenting with new or progressive back pain, motor/sensory deficits, and bowel or bladder dysfunction.

Monostotic vs Polyostotic

Descriptive classification terms for bone disorders: involving a single bone vs involvement of multiple bones.

Alkaline Phosphatase (ALP) & Gamma-Glutamyl Transferase (GGT)

Serum laboratory tests used to evaluate bone turnover; an elevated ALP with a normal GGT confirms that the ALP elevation is bone-derived (as seen in Paget disease or bone metastases) rather than liver-derived.

Denosumab

A RANKL inhibitor antibody used as a bone-modifying agent to reduce skeletal-related complications, such as pathologic fractures, in patients with bone metastases.

Cortical Bone

The dense, compact outer structural layer of bone surrounding the medullary cavity

Osteoporosis

A chronic skeletal disorder characterized by low bone mass, microarchitectural disruption, and skeletal fragility, leading to reduced bone strength and a significantly increased risk of fracture.

Osteopenia

A condition of low bone mineral density that is below normal levels but not low enough to meet the densitometric criteria for osteoporosis, defined by a DXA T-score between −1.0 and −2.5.

Osteoblasts

Specialized bone cells responsible for building and synthesizing new bone tissue during normal bone remodeling.

Osteoclasts

Specialized bone cells responsible for resorbing and breaking down old bone tissue.

Dual-Energy X-ray Absorptiometry (DXA/DEXA)

The preferred diagnostic imaging technique used to measure bone mineral density (BMD), most commonly evaluated at the lumbar spine, total hip, or femoral neck.

T-score

A densitometric measurement from a DXA scan that compares a patient's bone mineral density to that of a healthy young-adult reference population, serving as the diagnostic standard in postmenopausal women and men aged 50 or older.

Z-score

A densitometric measurement from a DXA scan that compares a patient's bone mineral density to age- and sex-matched peers, preferred for evaluation in premenopausal women, men under 50, and children.

Fragility Fracture

A fracture resulting from minimal trauma, such as a fall from standing height or less, most commonly occurring at the spine (vertebrae), hip, distal radius, or proximal humerus.

Fracture Risk Assessment Tool (FRAX)

A clinical calculator that estimates a patient's 10-year probability of hip fracture and major osteoporotic fracture by combining clinical risk factors with or without bone mineral density data.

Bisphosphonates

A primary class of antiresorptive medications (including alendronate, risedronate, ibandronate, and zoledronic acid) that increase bone density and reduce fracture risk by inhibiting osteoclast-mediated bone resorption.

Denosumab

A human monoclonal antibody antiresorptive therapy administered subcutaneously every 6 months that targets and inhibits RANKL, thereby preventing osteoclast formation, function, and survival.

Selective Estrogen Receptor Modulators (SERMs)

A class of medications (such as raloxifene) that act as estrogen agonists in bone to decrease bone resorption and reduce vertebral fracture risk while also reducing the risk of invasive ER-positive breast cancer.

Anabolic Agents teriparatide and abaloparatide

Bone-forming pharmacologic therapies that stimulate osteoblast activity and new bone synthesis through intermittent activation of parathyroid hormone (PTH) receptors.

Romosozumab

A monoclonal antibody targeting sclerostin that exerts a dual effect by simultaneously increasing bone formation and decreasing bone resorption.

RANKL

A key signaling protein involved in osteoclast differentiation and activation, which increases during estrogen deficiency and leads to accelerated bone resorption.

Sclerostin

An endogenous glycoprotein that inhibits bone formation, the targeted neutralization of which (via romosozumab) promotes osteoblastic activity and bone synthesis.

Osteonecrosis of Jaw

A rare but severe potential adverse effect associated with potent, long-term antiresorptive therapy, such as bisphosphonates or denosumab.

Atypical Femoral Fracture (AFF)

A rare adverse event linked to prolonged antiresorptive treatment, characterized by stress fractures along the subtrochanteric or diaphyseal region of the femur