Adamantinoma
Adamantinoma is an uncommon primary bone neoplasm with a strong predilection
for the tibia. Recent studies have confirmed the epithelial nature of this tumor.
Adamantinomas present most frequently during early adulthood as painful leg
masses with variable symptom duration, ranging from a few months to a few years.
These tumors appear in the tibial diaphysis as a well-circumscribed, eccentric,
lytic, sometimes multicystic lesion with surrounding sclerosis. The long bone
is often expanded and the cortex may or may not be intact, but there is no periosteal
reaction. The lesional tissue is grossly gray-white in color and rubbery-firm
in consistency, and cystic regions containing blood or straw-colored fluid may
be present. Adamantinomas have a wide variety of histologic appearances. Most
frequently, the tumor has a basaloid pattern, composed of groups of cells which
peripherally have palisading epithelial cells. Other histologic patterns are
tubular, spindle, and squamoid. Between these islands of epithelial cells is
a hypocellular, poorly organized, fibrous connective tissue, which often contains
areas resembling osteofibrous dysplasia. The tubular pattern may be confused
histologically with a vascular tumor. Immunohistochemical studies of adamantionma
demonstrate the presence of cytokeratin in the tumor cells, and absence of endothelial
markers. At the electron microscope level, the cells show epithelial features.
The treatment of adamantinoma is en bloc excision with amputation reserved for
large, unresectable, or recurrent lesions. This tumor has been reported to metastasize
to the lungs in approximately 20 to 25 percent of cases.
There is recent evidence in the literature that there is a new type of adamantinoma
called osteofibrous dysplasia-like or "differentiated" adamantinoma.
It is more common among younger patients, contains a prominent osteofibrous
dysplasia-like tissue, and has a good prognosis following curettage alone.
Chordoma
A chordoma is a rare tumor arising from remnants of the primitive notochord.
It is a solitary lesion found in the midline at either end of the spine, most
commonly first at the sacrococcygeal region (50 to 60 percent) and second at
the sphenooccipital region. Other sites of the spine are less frequently involved.
Chordomas have a predilection for middle-aged males and present with pain of
gradual onset and of long duration. There may be a large presacral rectal mass
that is palpable on rectal examination, and the patient may present with bowel
or bladder dysfunction from compression of the sacral roots. Chordomas of the
sphenoid or cervical spine may present with a cranial nerve palsy or nasopharyngeal
mass. Radiographically, the tumor is destructive and associated with an expansile
soft tissue mass. MRI or CT scan may help to delineate the extent of the tumor.
On gross inspection the tumor appears gray, lobulated, gelatinous, and encased
in a pseudocapsule. Histologically, the cells are polyhedral in shape and often
have eosinophilic cytoplasm and numerous vacuoles which displace the nucleus
(physaliphorous cells). The tissue has a lobular architecture and the cells
are disposed in cords, trabeculae, or sheets, which are separated by abundant
mucoid and myxoid matrix. Immunohistochemically, chordoma cells show positive
reaction to S-100 protein, cytokeratin, and epithelial membrane antigen. These
studies help to distinguish chordoma from other malignant tumors such as myxoid
chondrosarcomas and metastatic adenocarcinomas.
Wide local resection is the recommended treatment; however, because the patients
often present late in the clinical course and because of its close proximity
to neurologic structures, the tumor is usually not resectable. Radiation is
indicated. These tumors have a very high rate of recurrence even with surgical
treatment. Metastases develop rather frequently to the lungs, liver, and other
tissues.
A small percentage of chordomas of the sphenooccipital region have a prominent
chondroid component and are designated as chondroid chordomas. They apparently
have a better prognosis than conventional chordomas. Rarely, chordomas may have
a high-grade sarcomatous component adjacent to it, usually resembling malignant
fibrous histiocytoma. These tumors are called dedifferentiated chordomas and
have a bad prognosis.
Lipoma
Lipomas primary in bone are rare. They occur in adults and predilect the femur,
fibula, tibia, and calcaneous. Radiographs demonstrate a lytic lesion with well-defined
margins. Central areas of radiodensity may be seen. MRI is helpful in the diagnosis
of lipoma, showing high signal intensity in both T1- and T2-weighted images.
Histologically, there is mature adipose tissue with atrophic bone trabeculae.
Fat necrosis and calcification also may be seen. Treatment is by curettage.
Liposarcoma is exceedingly rare.
Leiomyosarcoma
Leiomyosarcoma is a rare tumor affecting adults and most commonly predilecting
the femur and tibia. Radiographs show nonspecific lytic changes of a malignant
nature. Histologically, there are spindle cells with acidophilic cytoplasm,
and the nuclei show varying degrees of atypia and mitotic activity. There is
a dense fascicular pattern. Immunohistochemical reactivity to muscle markers
are important findings in order to differentiate this tumor from malignant fibrous
histiocytoma and fibrosarcoma. En bloc resection or amputation is recommended.
At least 50 percent of patients die of metastases. Primary leiomyosarcoma of
bone should be distinguished clinically from metastatic leiomyosarcoma to bone,
particularly from the uterus.
Schwannoma
Intraosseous schwannoma (neurilemmoma) is rare and arises from the sacrum, mandible,
and other bones. Radiographically, it is a lytic lesion, and microscopically,
it shows the typical features of Antoni A and B tissue as seen in the soft tissue
counterpart. In most cases of neurofibroma with bone involvement, the tumors
are located in the soft tissue with secondary extension into bone.
