Published Works: Fibrous
And Fibrohistiocytic Tumors
Benign
Tumors
Benign
Fibrous Histiocytoma
Benign fibrous histiocytoma is a rare lesion that is microscopically indistinguishable
from a nonossifying fibroma. It occurs exclusively in adults, often older than
25 years of age. The pelvis and the ribs are the most common sites for a benign
fibrous histiocytoma. The tumor may also be found in the skull and vertebrae.
In the long bones, it tends to appear in the diaphyseal region. The epiphyseal
lesions may be indistinguishable histologically from giant cell tumor. Regardless
of their location, these lesions are always painful, a characteristic that clearly
distinguishes the tumor from a nonossifying fibroma which is usually painless.
Controversy exists as to whether benign fibrous histiocytoma is a distant entity
or a reactive lesion associated with a preexisting condition. The prognosis
of benign fibrous histiocytoma is similar to other benign fibrous tumors and
treatment with curettage and bone grafting has been demonstrated to prevent
recurrence.
Desmoplastic Fibroma
Desmoplastic fibromas are rare, benign aggressive fibrous lesions seen in adolescence
and young adulthood. They occur in the metadiaphyseal region of long bones such
as the femur, tibia, and humerus, as well as the pelvis and jaws. On radiograph
they are lytic lesions with cortical thinning, and the margins may be sharp
or ill-defined. A trabecular pattern may be present within the lesion. Histologically,
the tumor consists of abundant collagen fibers and small benign-appearing fibroblasts,
and resembles fibromatosis. Microscopic extensions into adjacent reactive bone
are present and may account for the recurrence in reported cases treated with
curettage and bone grafting. Intralesional curettage is the treatment of choice.
Differentiation between desmoplastic fibroma and low-grade fibrosarcoma may
be difficult and sometimes both lesions overlap.
Malignant Tumors
Malignant Fibrous
Histocytoma
Malignant fibrous histiocytoma of bone was described in 1972 as a neoplasm composed
of spindle cells, histiocytic-type cells, and giant cells, with spindle-cells
disposed in a fascicular arrangement that is called storiform pattern. Recent
studies suggest that this tumor derives from fibroblasts rather than histiocytes.
It frequently arises in the metadiaphyseal region of long bones of adults, most
often the distal femur. The symptoms of pain and swelling associated with a
tender mass, usually present for at least 6 months, are the most common presenting
complaints. The lesions appear lytic on radiograph. There is cortical destruction
with minimal periosteal reaction, and a soft tissue mass can be seen on the
plain film. Histologically, the lesional tissue features spindle cells and histiocytoid
cells, as well as scattered multinucleated giant cells and lipid-laden histiocytes.
The spindle cells are often arranged in a storiform or cartwheel pattern, where
they form fascicles that intersect in a central hypocellular area. The cells
show a varying degree of cell pleomorphism. Many cases that were originally
diagnosed as fibrosarcoma are now reclassified as malignant fibrous histiocytoma.
Osteosarcomas and leiomyosarcomas have areas that resemble malignant fibrous
histiocytoma, but proper tissue sampling and immunohistochemical studies are
helpful in the differential diagnosis. The surgical treatment involves a wide
resection. The benefits of chemotherapy are inconclusive. Five-year survival
rate is approximately 50 percent. Malignant fibrous histiocytoma may result
from malignant transformation of bone involved with Paget’s disease, bone
infarct, or previous radiation therapy for an unrelated tumor. Patients with
this secondary malignant fibrous histiocytoma have a poor prognosis.
Fibrosarcoma
Fibrosarcoma is a primary malignant tumor that arises from fibroconnective tissue
of the marrow cavity. Secondary fibrosarcoma can arise from a precursor lesion
such as a bone infarct or Paget’s disease, or from a precursor lesion
such as a bone infarct or Paget’s disease, or from previously irradiated
bone. The tumor may occur at any location; however, it has a strong predilection
for the metaphyseal region of the femur and tibia. Patients with primary fibrosarcoma
of the bone present in the middle decades of life and may have longstanding
complaints of pain and swelling prior to seeking medical attention. The lesion
has an aggressive nonspecific appearance on radiograph. They are usually large,
eccentrically based lytic lesions that are poorly marginated and often lack
a rim of reactive sclerosis. Cortical destruction with erosion into the soft
tissues may occur. Microscopically, the tumor is comprised of spindle cells
arranged in a "herringbone" pattern. The spindle cells from low-grade
lesions demonstrate little cellular atypia and few mitotic figures, while the
high-grade tumors have marked pleomorphism and significant mitotic activity.
Fibrosarcoma should be differentiated histologically from fibroblastic osteosarcoma
and malignant fibrous histiocytoma, but this distinction is often difficult.
It is possible that many fibrosarcomas are examples of malignant fibrous histiocytoma.
Fibrosarcoma is treated with a wide resection. Radiation therapy may be of use
for surgically inaccessible lesions. The overall prognosis for fibrosarcoma
of bone is approximately 50 percent survival rate at 5 years.
