Classification and main groups
Skeletal tumors show great diversity. Depending on their origin, three main categories are distinguished: bone-forming, cartilage-forming, and bone marrow neoplasms.
The basic division of true tumors is as follows:
- From bone tissue: benign (osteomas) and malignant (osteosarcomas).
- From cartilage tissue: benign (chondromas) and malignant (chondrosarcomas).
Tumor-like lesions (fibrous cortical defect, non-ossifying fibroma) are also distinguished, which have a favorable prognosis and can heal spontaneously.
Benign bone-forming tumors
This group is characterized by slow growth, clear borders, and the absence of cellular atypia. However, incomplete surgical removal frequently leads to recurrences.
- Osteoma: a dense lesion with a lobulated surface. Microscopically characterized by narrowing of the bone marrow space (replaced by fibroreticular tissue) and the absence of osteoclasts.
- Osteoid osteoma: appears as a granular red mass. It consists of interweaving osteoid trabeculae bordered by active osteoblasts. Typical in children and adolescents.
- Osteoblastoclastoma (giant cell tumor): most frequently occurs in the epiphyses and metaphyses of long tubular bones in patients aged 20–40 years. On cross-section, the tissue is friable, variegated brown-yellow due to hemorrhages. It contains cysts with bloody fluid and numerous osteoclast-like cells. It is capable of destructive growth and metastasis despite its benign status.
Malignant bone-forming tumors
The key representative of this group is osteosarcoma (osteogenic sarcoma). It has three histological variants: osteoblastic, chondroblastic, and fibroblastic.
- Central osteosarcoma: the most common form, growing within the medullary cavity. It has a yellow-brown color with alternating dense and soft areas (necrosis, cysts). Cells are arranged haphazardly or form a moiré pattern. Hematogenous metastasis and an unfavorable prognosis are characteristic.
- Peripheral osteosarcoma: grows on the surface, invading the cortical plate. It appears as a gray-bluish lobulated nodule. With radical removal, the prognosis is favorable (low-grade variants are an exception).
Other sarcomas include fibrosarcoma of the bone, which forms bundles of atypical collagen fibers, and malignant fibrous histiocytoma (a soft brown nodule with areas of necrosis). Both tumors are distinguished by aggressive infiltrative growth.
Cartilage-forming tumors
- Chondroma: a benign neoplasm of hyaline cartilage. Most commonly affects the bones of the hands and feet. Cells are arranged haphazardly and have pyknotic nuclei. Secondary changes are possible: mucous degeneration, necrosis, hemorrhages. The variant inside the bone is called enchondroma, and beneath the periosteum, periosteal chondroma.
- Chondrosarcoma: the malignant counterpart. Affects large flat and tubular bones (ribs, pelvis, sternum). The primary mesenchymal form is typical for older individuals, whereas the secondary form (arising from the malignant transformation of a benign chondroma) is frequently encountered in young patients.
The role of inflammation in tumor development
Malignant bone neoplasms can arise not only primarily, but also as a complication of prolonged pathological processes.
For example, chronic hematogenous osteomyelitis (the outcome of acute purulent inflammation) is accompanied by the formation of bone cavities, sequestra, and fistulae. The prolonged course of this disease can lead to secondary amyloidosis, pathological fractures, and even the appearance of tumors directly within the chronic lesion zone.
Briefly: answers to topical questions
What tumor-like bone diseases are distinguished in pathological anatomy?
Tumor-like diseases of bone tissue include:
- Fibrous cortical defect — an area of bone consisting of interweaving bundles of connective tissue and diverse cells without signs of atypia.
- Non-ossifying fibroma — a painful lesion located in the metaphyses of tubular bones.
Which neoplasms belong to the group of bone marrow tumors?
Ewing sarcoma belongs to the group of bone marrow tumors.
- Ewing sarcoma — a malignant bone marrow tumor developing predominantly in childhood and adolescence.
Macroscopically, it is a soft tissue mass with numerous hemorrhages and areas of necrosis. Microscopically, it consists of densely packed small atypical cells with hyperchromatic nuclei and irregular mitoses; the matrix is barely detectable. It is characterized by rapid growth and early hematogenous metastasis.
Which genetic mutations and syndromes are associated with the development of osteosarcoma?
Familial retinoblastoma is associated with the development of osteosarcoma, featuring a mutation in the Rb gene and an increased risk of osteosarcomas. Additionally, cases of orbital osteosarcoma have been described following radiation therapy for retinoblastoma.
To remember the aggressive feature of the benign giant cell tumor, use the abbreviation DOLg: Denign Osteoblastoclastoma Leaves for the Gchest (metastasizes to the lungs).
Class and exam questions
What is the difference between osteoid osteoma and osteoblastoma?
Histologically, these neoplasms are completely identical. The differences lie exclusively in their clinical manifestations.
What happens to bone tissue in malignant osteoblastoclastoma?
The tumor exhibits destructive invasive growth. It destroys the cortical layer of the bone and actively invades the surrounding soft tissues, forming foci of necrosis and hemorrhage.
Which form of osteosarcoma is considered prognostically more favorable?
Peripheral (surface) osteosarcoma has a favorable prognosis provided there is timely and radical excision. The only exceptions are its low-grade variants.
What else to study on this topic
- Pathogenesis and stages of acute hematogenous osteomyelitis
- The sequestration process in chronic purulent bone inflammation
- Histological differences between central and peripheral osteosarcomas
- Criteria for malignant transformation of cartilage-forming tumors
- Differential diagnosis of fibrous cortical defect and fibrosarcoma
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