Pleomorphic undifferentiated sarcoma (abbreviated PUS), also undifferentiated pleomorphic sarcoma and previously malignant fibrous histiocytoma (abbreviated MFH), is a type of soft tissue sarcoma.
It is considered a diagnosis of exclusion for sarcomas that cannot be more precisely categorized.
Epidemiology
PUS is regarded as the most common soft tissue sarcoma of late adult life. It rarely occurs in children. It occurs more often in Caucasians than in those of African or Asian descent and is a male-predominant disease, afflicting two males for every female.
Presentation
PUS occurs most commonly in the extremities and retroperitoneum, but has been reported in other sites. Metastasis occurs most frequently in the lungs (90%), bones (8%), and liver (1%).
In the extremities, it presents itself as a painless enlarging soft tissue mass.
Diagnosis
It can be detected by magnetic resonance imaging (MRI), but a biopsy is required for the definitive diagnosis. MRI findings typically show a well-circumscribed mass that is dark on T1-weighted images and bright on T2-weighted images. Central necrosis is often present and identifiable by imaging, especially in larger masses.
Pathology
Pleomorphic undifferentiated sarcomas are, by definition, undifferentiated, meaning (as the name implies) that they do not bear a resemblance to any normal tissue.
The histomorphology, otherwise, is characterized by high cellularity, marked nuclear pleomorphism, usually accompanied by abundant mitotic activity (including atypical mitoses), and a spindle cell morphology. Necrosis is common and characteristic of high grade lesions.
Treatment
Treatment consists of surgical excision (the extent of which ranges from tumor excision to limb amputation, depending on the tumor) and in some cases radiation. Chemotherapy remains controversial in MFH. The usual site of metastatic disease is the lungs, and metastases should be resected if possible.
Prognosis
Prognosis depends on the primary tumor grade (appearance under the microscope as judged by a pathologist), size, resectability (whether it can be completely removed surgically), and presence of metastases. The five-year survival ranges from 35 to 60%.
Human-human transmission
There is a case report of human-human transmission, in a surgeon who injured his hand while working on a PUS case.
References
External links
- Malignant Fibrous Histiocytoma (MFH) - Sarcoma Learning Center