Fibrosarcoma
Synonyms and keywords: Malignant fibromatous neoplasm, Fibroblastic sarcoma; Malignant fibrous histiocytoma

# Overview
Fibrosarcoma (fibroblastic sarcoma) is a malignant tumor derived from fibrous connective tissue and characterized by immature proliferating fibroblasts or undifferentiated anaplastic spindle cells.  Fibrosarcoma is classified into 3 grades: low grade (differentiated), intermediate, and high grade (anaplastic).  There are 3 stages of fibrosarcoma based on the grade and extent of the lesion.  The tumor may be localized at the end of the long bones. Most often it affects the upper end of tibia or lower end of femur.  Fibrosarcoma is a rare disease that affects approximately one in two million people annually.  Patients of all age groups may develop fibrosarcoma, but are most common between the third and sixth decades of life. Fibrosarcoma is associated with a 5-year survival rate of 30% among patients with high grade medullary lesions and 50-80% among patients with surface fibrosarcomas and low grade fibrosarcomas.  Common risk factors for the development of fibrosarcoma are preexisting benign lesions, radiation therapy, surgically treated fractures, and infarction of bone.  The most common symptoms of fibrosarcoma include pain, swelling, loss of range of motion.  Fibrosarcoma must be differentiated from other conditions that cause pain, swelling, and lesions that may appear similar to fibrosarcoma on radiological imaging.

# Classification

## Grade
Fibrosarcoma may be classified according to degrees of differentiation into three subtypes
- Low grade malignancy (differentiated)
- Intermediate malignancy
- High grade malignancy (anaplastic)

## Stage
Fibrosarcoma may be classified into 3 stages based on grade and extent of lesion.
- Stage I
Stage IA: Low grade lesion that is confined to its anatomic compartment
Stage IB: Low grade lesion that have extended outside of its compartment
- Stage II
Stage IIA: High grade lesion that is confined to its anatomic compartment
Stage IIB: High grade lesion that have extended outside of its compartment
- Stage III
lesions are any grade or anatomic site that have metastasized

# Pathophysiology

## Gross Pathology
The tumor may be localized at the end of the long bones. Most often it affects the upper end of tibia or lower end of femur. The tumor is typically well demarcated but not encapsulated.

## Microscopic Pathology
Tumor cells may resemble mature fibroblasts (spindle-shaped), secreting collagen, with rare mitoses. These cells are arranged in short fascicles which split and merge, giving the appearance of "fish bone". Poorly differentiated tumors consist in more atypical cells, pleomorphic, giant cells, multinucleated, numerous atypical mitoses and reduced collagen production. Presence of immature blood vessels (sarcomatous vessels lacking endothelial cells) favors the bloodstream metastasizing. The malignant cells are characteristically arranged in a "herringbone" pattern.

# Epidemiology and Demographics
Fibrosarcoma accounts for about 5% of all primary bone sarcomas.

## Incidence
Fibrosarcoma is a rare disease. Worldwide, the incidence of fibrosarcoma is 0.05 per 100,000 persons.

## Age
Patients of all age groups may develop fibrosarcoma, but are most common between the third and sixth decades of life. In infants, fibrosarcoma is usually congenital. Children presenting with fibrosarcoma usually do so in the first two years of their life.

## Gender
It affects men and women equally.

# Natural History, Complications, and Prognosis

## Prognosis
- Prognosis of fibrosarcoma depends on the tumor grade. It is associated with a 5-year survival rate of 30% among patients with high grade medullary lesions and 50-80% among patients with surface fibrosarcomas and low grade fibrosarcomas.
- Secondary sarcoma, presence of eccentric permeative lesions, primary tumor in the axial skeleton are associated with a particularly poor prognosis among patients with fibrosarcoma.

# Risk Factors
Common risk factors for the development of fibrosarcoma are preexisting benign lesions such as:
- Giant cell tumor
- Enchondroma
- Fibrous dysplasia
- Bizarre parosteal osteochondromatous proliferation
- Chronic osteomyelitis
Other risk factors include Paget's disease, radiation therapy, surgically treated fracture and infarction of bone.

# Screening
Screening for fibrosarcoma is not recommended.

# History and Symptoms
The most common symptoms of fibrosarcoma include:
- Localized Pain
- Swelling
- Loss of range of motion
Pain with weight-bearing that is relieved by rest and night pain may be observed. Many patients with fibrosarcoma neither feel sick nor experience classic symptoms of cancer such as weight loss and fatigue. Sometimes, patients with fibrosarcoma may present with pathological fracture of the affected bone.

# Differential Diagnosis
Fibrosarcoma must be differentiated from other conditions that cause pain, swelling, and lesions that may appear similar to fibrosarcoma on radiological imaging such as
- Osteosarcoma
- Chondrosarcoma
- Leiomyosarcoma
- Malignant fibrous histiocytoma
- Myofibromatosis
- Desmoplastic fibroma
Intra-osseous fibrosarcoma that affects the jaw must be differentiated from odontogenic sarcomas such as
- Ameloblastic fibrodentinosarcoma
- Ameloblastic fibrosarcoma
- Odontogenic carcinosarcoma

# Diagnosis

## X Ray
The radiological picture of fibrosarcoma typically shows the osteolytic lesion  with a permeative or moth-eaten appearance. Margins of lesion can range from well-demarcated to ragged appearance.

## CT scan
CT scan is performed at initial diagnosis of fibrosarcoma to determine the metastasis of the tumor to the lungs. The lungs are most common site of fibrosarcoma metastasis.

## MRI
MRI of the entire bone is necessary among patients with fibrosarcoma. The benefits include:
- Determination of the extent of bone marrow and soft tissue involvement
- Identification of non-contiguous skip lesions that can arise within the same bone

# Treatment
- Surgery is the mainstay of treatment for fibrosarcoma.
- Chemotherapy and radiation therapy have not proven to be effective.
- Radiation therapy may be administered as palliative therapy.