Bone Tumors
Intracortical Osteosarcoma
Intracortical osteosarcoma is an extremely rare type of osteosarcoma that arises within and is usually confined to the cortex of the bone.
It is a high grade osteosarcoma that is confined to the cortex of a long bone
Intracortical osteosarcoma is very rare and only a handful of cases have been reported.
It is often initially misdiagnosed as an osteoid osteoma, bone abscess, non ossifying fibroma, osteoblastoma or adamantinoma until it is biopsied or removed
CLINICAL PRESENTATION
Signs/Symptoms: Pain, swelling, tenderness, <1 year
Sex Predilection: Possible slight male predilection
Age: 10-30 years
Sites: Diaphysis of femur or tibia are the most common sites
RADIOGRAPHIC PRESENTATION
Plain Radiographs:
Intracortical lytic lesion with surrounding sclerosis
The junction of the lesion with the normal bone is usually irregular but sharply demarcated
Size of lesion is usually between 1 cm to 5 cm
Lesion may demonstrate ossification or mineralization within it
No intramedullary or soft tissue involvement
Minimal or no periosteal reaction or periosteal reaction may appear benign
CT may show cortical permeation
GROSS PATHOLOGY
Intracortical, well defined tumor with very thick expanded cortex
Irregular borders
Thick and expanded cortex
Tumor is grey/tan/yellow and gritty from mineralized osteoid or bone production
MICROSCOPIC PATHOLOGY
Highly osteoblastic & sclerotic similar to a conventional osteosarcoma
Neoplastic cells when become entrapped in osteoid may appear to normalize and have less nuclear pleomorphism and atypia
Residual cortical bone will be entrapped by malignant cells producing osteoid (evidence of malignancy)
There may be very small chondrosarcomatous and fibrosarcomatous foci
Cartilage production is minimal (as opposed to a periosteal osteosarcoma)
Malignant spindle cell tumor producing osteoid
Malignant cells have large nuclei, minimal cytoplasm, nuclear pleomorphism, mitoses
They appear crowded and haphazard
The osteoid is layed down in lace-like manner in between malignant cells
DIFFERENTIAL DIAGNOSIS
Osteoid Osteoma
Brodie's Abscess
Osteoblastoma
Nonossifying fibroma
Eosinophillic Granuloma
Osteofibrous Dysplasia
Adamantinoma
TREATMENT
En bloc Resection/Limb Sparing Surgery whenever feasible
Patients treated by curettage and intralesional procedures have experienced local recurrences according to the literature
Efficacy of chemotherapy is uncertain given the small number of cases
PROGNOSIS
Metastases to the lungs along with unusual sites of metastases have been reported
Exact statistics are unavailable given the small number of patients who have been reported to develop this disease.
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