Page 593 - Concise Pathology for Exam Preparation ( PDFDrive )

578 SECTION II Diseases of Organ Systems

• The stroma is frankly sarcomatous, composed of large atypical spindle-shaped cells with
bizarre tumour giant cells and frequent mitoses.
• There is direct formation of tumour osteoid by neoplastic cells. Osteoid is arranged in a
thin anastomosing lace-like pattern and appears eosinophilic, glassy and homogenous
on H&E sections.
• Chondroblastic and fibroblastic elements may also be present besides osteoid.
• Spontaneous necrosis and vascular invasion are frequent.
Surface osteosarcomas
• Juxtacortical (parosteal)
• Slow growing.
• Classically, located on the posterior aspect of lower femur.
• Large lobulated mass encircling the bone.
• Low-grade tumor with a good prognosis.
• Periosteal osteosarcoma
• Grows on the surface of long bones.
• Occurs on periosteal surface between cortex and periosteum.
• Prominent cartilaginous component.
• High-grade osteosarcoma; poor prognosis.
• Osteosarcoma of jaw
• Affects older age.
• Involves mandible and alveolar ridges of maxilla.
• Prominent chondroblastic component.
• Good prognosis.
• Osteosarcoma in Paget’s disease
• Multicentric.
• Pelvis, humerus, and femur bones are involved in that order of frequency.
• Poor prognosis.
Prognosis
• Lungs, other bones, pleura and heart are common sites of metastases. Regional lymph
nodes are however rarely involved.
• Long-term survival rate with chemotherapy and limb salvage therapy is 60–70%.

Q. Describe the gross and microscopic features of the common
cartilage-forming tumours.
Ans. Cartilaginous neoplasms of bone are characterized by formation of hyaline or myxoid
cartilage.

Classification
Benign:
• Osteochondroma
• Chondroma
• Chondroblastoma
• Chondromyxoid fibroma
Malignant:
Chondrosarcoma

Osteochondroma (Exostosis)
• The most frequent benign bone tumour, osteochondroma presents as a bony outgrowth
capped by hyaline cartilage which is attached to the underlying bone.
• Multiple osteochondromas occur in the setting of multiple hereditary exostoses, an
autosomal dominant condition, which is associated with inactivation of EXT genes
(EXT1 and 2). Solitary osteochondromas are thought to arise from displacement of
lateral portion of the growth plate.

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