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.



  • Pleomorphic sarcoma

  • Undifferentiated high-grade sarcoma

  • Malignant fibrous histiocytoma (MFH)


  • 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


Environmental Exposure

  • Can occur at site of previous irradiation

  • Rarely secondary to chronic ulceration or scarring



  • 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


  • 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


  • Enlarging mass

    • Painful or painless

  • Small proportion of patients have metastases at presentation


  • 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
Premium Wordpress Themes by UFO Themes
%d bloggers like this: