Undifferentiated Pleomorphic Sarcoma



Undifferentiated Pleomorphic Sarcoma


Khin Thway, BSc, MBBS, FRCPath









Gross photograph of pleomorphic undifferentiated sarcoma shows lobulated tumor within skeletal muscle and focally abutting the subcutis image. Necrosis is a prominent feature image.






Microscopically, pleomorphic undifferentiated sarcoma is hypercellular with sheets of markedly anaplastic spindle and epithelioid cells, including bizarre image and multinucleated image forms.


TERMINOLOGY


Synonyms



  • Pleomorphic sarcoma


  • Undifferentiated high-grade sarcoma


  • Malignant fibrous histiocytoma (MFH)


Definitions



  • Anaplastic sarcoma composed of pleomorphic spindle and polygonal cells


  • No other definable differentiation, other than fibroblastic or myofibroblastic


  • Morphologic pattern shared by poorly differentiated or anaplastic tumors of different lineages



    • Diagnosis of pleomorphic sarcoma is therefore one of exclusion


ETIOLOGY/PATHOGENESIS


Environmental Exposure



  • Can occur at site of previous irradiation


  • Rarely secondary to chronic ulceration or scarring


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Most common adult soft tissue sarcoma


    • Incidence increases with age


  • Age



    • Older adults


    • Very rare in adolescents and young adults


  • Gender



    • Slight male predominance


Site



  • Deep soft tissue


  • Most in extremities



    • Lower limb > upper limb


  • May also arise on trunk


  • Most intraabdominal examples represent dedifferentiated liposarcoma


  • Smaller numbers occur superficially


Presentation



  • Enlarging mass



    • Painful or painless


  • Small proportion of patients have metastases at presentation


Prognosis



  • Usually high-grade tumors


  • Local recurrence in up to 1/3 of cases


  • Pulmonary metastases in up to 1/2 of cases


  • Superficial tumors have better prognosis than deep ones


  • Myoid differentiation is prognostically adverse, with earlier metastasis



    • Applies whether differentiation is morphologic (leiomyosarcoma, myofibrosarcoma, rhabdomyosarcoma) or only immunohistochemical (actin, desmin)


  • Dedifferentiated liposarcoma has comparatively low metastatic rate

Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Undifferentiated Pleomorphic Sarcoma
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