Bone tumors

1-Primary bone tumors Benign Malignant 2- Secondary (metastatic) bone tumors

[I] Primary Bone Tumors I. Bone Forming Tumors (Osteoblastic) They are characterized by osteoid formation by Tumor cells. (A) Benign Tumors: Osteoma, Osteoid osteoma, and Osteoblastoma (B) Malignant Tumors: Osteosarcoma (osteogenic sarcoma).

(B) Malignant Bone Forming Tumors Osteosarcoma (Osteogenic Sarcoma) Is a malignant Tumor of mesenchymal origin in which the neoplastic cells produce osteoid and/or bone. Excluding multiple myeloma, osteosarcoma is the most common primary malignant tumor of bone.

Types: Primary, Secondary 1.Primary (Classic or Conventional) Osteosarcoma: Age: It occurs during the second decade of life. Sex: Males are more affected than females Sites: It arises in the metaphyseal ends of long bone, around knee joint (proximal tibia and distal femur) arises de novo from a previously normal bone

Morphology: Grossly, Tumor is present at metaphyseal end of long bone Morphology: Grossly, Tumor is present at metaphyseal end of long bone. Is fusiform, fading on the shaft giving a "mutton leg" appearance. Is gray-white, often showing haemorrhage and cystic softening. Bone necrosis associated with new bone formation especially noticed in the subperiosteal area.

Osteosarcoma is highly aggressive, it destroys the cortex extending inwards into the medullary cavity and outwards into the adjacent soft tissue. It rarely involves the joint cavity, usually the epiphysis is spared

Microscopically, Tumor cells are either spindle shaped and uniform, or pleomorphic with bizarre, hyperchromatic nuclei and frequent mitotic figures. Giant cells sometimes mistaken for osteoclasts are often seen. Tumor cells produce osteoid which is marked by trapping of the malignant cells within a homogeneous pink osteoid matrix and is surrounded by a rim of malignant osteoblasts.

Radiologically, when the neoplasm penetrates the cortex, it lifts the periosteum producing the so called "Codeman's triangle". This triangle is the angle between the plane of outer surface of the cortex and the elevated periosteum. It is characteristic but not pathognomonic of osteosarcoma. Also, new bone formation is patchy in the form of fine spicules of bone radiating out from the central mass of Tumor tissue, giving "sun ray" appearance.

Clinical features'. Progressive enlarging painful mass, usually seen after a fracture of the bone involved. Aggressive tumor metastasizes early by blood reaching the lungs and other sites. Lymph node metastasis is unusual.

Diagnosis:. Depends on age, site, size, and raised serum alkaline phosphatase. X-ray radiograph revealing mass at metaphyseal end of long bone, showing Codeman’s triangle, sun ray appearance of new bone, extraosseous radiodensities (due to penetration of cortical bone and extension in soft tissue). Biopsy from such soft tissue extensions is necessary to confirm diagnosis.

Prognosis: It depends on the size and histologic type of the Tumor Prognosis: It depends on the size and histologic type of the Tumor. Fibroblastic osteosarcoma has the best prognosis

Secondary Osteosarcoma: It occurs in older age than the conventional type, usually above 40 years arises as a complication of a pre-existing bone lesion e.g. Paget's disease, bone infarct, and a previously irradiated bone and rarely in patients with fibrous dysplasia and chronic osteomyelitis. It is a highly aggressive tumor that responds less favorably to treatment than does conventional osteosarcoma.

Giant Cell Tumor of Bone (Osteoclastoma ) Locally aggressive neoplasm of bone. Occurs in adults 20-40 years, with slight female predominance. Arises in epiphysis of long bones. Over 50% occur around knee joint (distal femur and proximal tibia). Also found in proximal humerus and distal radius

Histogenesis of giant cell Tumor is unknown Histogenesis of giant cell Tumor is unknown. The current opinion suggests that giant cells are reactive cells derived from macrophages, and proliferating mononuclear cells are the neoplastic component.

Morphology: Usually solitary, rarely multiple or multicentric Morphology: Usually solitary, rarely multiple or multicentric. Grossly, appears as large red brown mass containing large areas of necrosis and cystic changes. Remnants of residual bone are found traversing the necrotic tissue. No new bone formation is noticed.

Microscopically, composed of 2 elements: a. Mononuclear cells: the neoplastic component of the neoplasm. They are round to spindle-shaped cells, and have vesicular nuclei.

b. Multinucleated giant cells: The reactive component of the neoplasm b. Multinucleated giant cells: The reactive component of the neoplasm. They closely resemble osteoclasts, contain a huge number of vesicular nuclei (100 or more) and are evenly distributed in the neoplasm. Stroma of the tumor is scanty and contains areas of haemorrhage necrosis, and haemosiderin pigments

Clinical features: Pain, tenderness, functional disability, occasional fracture. Radiologically, large, lytic, "soap-bubble" lesion, erodes into the subchondral bone plate. Overlying cortex is destroyed and bulging soft tissue mass appears delineated by a thin shell of reactive bone.

Biologic behavior: Is unpredictable Biologic behavior: Is unpredictable. Majority of recurrences are common after simple curettage sarcomatous change may occur and occasionally metastases to the lung may occur

IV. Myelogenic Tumors of Bone Malignant lymphoma, Leukemias, and Multiple myeloma (plasma cell myeloma)

Plasma Cell Myeloma (Multiple Myeloma) It is a plasma cell neoplasm that originates in the bone marrow. It is characterized by involvement of the skeleton at multiple sites and may spread to many extraosseous sites. Most common bones affected are: vertebral column, ribs, skull, pelvis, femur, clavicle, and scapula. Occurs between 50-60 years, both sexes are affected equally.

Morphology: Grossly, focal lesion that begins in the medullary cavity, then it erodes the cancellous bone and destroys cortical bone. On section, the bony defects are filled with soft, red, gelatinous tissue. Microscopically, there is increase in the number of plasma cell constituting about 90% of all cells of the bone marrow. The cells may be well differentiated, or may be large and pleomorphic

Multiple myeloma ME

Replacement of bone marrow by neoplastic cells will lead to anemia. Tumor cells produce excessive gammaglobulins damaging the kidney. Abnormal serum proteins arc formed, leading to appearance of Bence-Jones protein in the urine. Pyelonephritis occurs due to high liability to infection. Plasma cell infiltrates may be encountered in the spleen, liver, lungs, nerve trunk roots, and lymph nodes. Systemic amyloidosis of the A1-type occurs in 10% of the patients

[II] Metastatic Tumors to the skeleton (Secondary tumors of bone) Most common form of skeletal malignancy. Pathway of spread is mostly haematogenous. 70% of metastases occur in axial skeleton (cranium, ribs, spine, and sacrum), and 30% occur in long bones at metaphyseal region

Clinical features: Pain and pathologic fractures. Anemia Pneumonia ■ Pyelonephritis and renal insufficiency. Prognosis: Variable

In adults over half of the skeletal metastases originate from cancers of prostate, breast, kidney lung and thyroid. In children secondary involvement of skeleton, most commonly from neuroblastoma, Wilm’s Tumor, osteosarcoma, Ewing's sarcoma, and rabdomyosarcoma

Most metastases of bone are lytic (destroying) e. g Most metastases of bone are lytic (destroying) e.g. carcinoma of thyroid, breast, kidney, lung and gastrointestinal tract. Osteosclerotic metastases (bone forming) e.g. prostate cancer. Mixed osteolytic and osteosclerotic metastases (bone forming and bone destroying) occur in most of the metastases.