Pleomorphic undifferentiated sarcoma

Pleomorphic undifferentiated sarcoma
Classification and external resources
Micrograph of a pleomorphic undifferentiated sarcoma. H&E stain.
ICD-10	C49 (ILDS C49.M10)
OMIM	8830/3
DiseasesDB	31471
eMedicine	radio/420
MeSH	D051677

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 are regarded as the most common soft tissue sarcoma of late adult life. It rarely occurs in children. It occurs more often in Caucasians, than 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 occur most frequently in the lungs (90%), bones (8%) and liver (1%).

In the extremities, it presents 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 shows 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 (as the name implies) meaning 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 cut-out completely), and presence of metastases. The five-year survival ranges from 35-60%.

Human-human transmission

There is a case report of human-human transmission, in a surgeon that injured their hand while working on a PUS case.

External links

• Malignant Fibrous Histiocytoma (MFH) - Sarcoma Learning Center