Dedifferentiated Liposarcoma



Dedifferentiated Liposarcoma


Thomas Mentzel, MD









Gross pathology photograph shows an abrupt transition from atypical lipomatous tissue image to a larger, nonlipogenic sarcomatous component image.






Hematoxylin & eosin shows dedifferentiated nonlipogenic sarcoma (left) with an abrupt transition from atypical lipomatous tumor (right). Note the sharp demarcation between the 2 components.


TERMINOLOGY


Abbreviations



  • Dedifferentiated liposarcoma (DDLS)


Definitions



  • Malignant lipogenic neoplasm with abrupt or gradual transition from atypical lipomatous tumor to nonlipogenic sarcoma of variable histology


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Occurs in ˜ 10% of cases of atypical lipomatous tumor


    • 90% arise de novo, 10% in local recurrences


    • Retroperitoneum, intraabdominal cavity are more frequently involved than extremities, spermatic cord, head/neck region, trunk


    • Mainly in deep soft tissues


    • Very rare in subcutaneous and dermal tissues


    • Probably represents time-dependent phenomenon


  • Age



    • Middle-aged to elderly patients


  • Gender



    • M = F


Presentation



  • Large, painless mass


  • Slowly growing neoplasm


  • Often longstanding mass exhibiting recent increase in size


Treatment



  • Surgical approaches



    • Complete excision with tumor-free margins


Prognosis



  • Recurs locally in ≥ 40% of cases


  • Distant metastases observed in 15-20% of cases


  • Overall mortality 25-30% at 5-year follow-up


  • Anatomic location is most important prognostic factor


  • Retroperitoneal, intraabdominal lesions exhibit worst clinical behavior


  • Superficial neoplasms have good prognosis


  • Amount and morphological grade of nonlipogenic areas not of prognostic importance


IMAGE FINDINGS


General Features



  • Best diagnostic clue



    • Coexistence of fatty and non-fatty-solid components


  • Location



    • Retroperitoneum, intraabdominal cavity, deep soft tissues


  • Size



    • Large size, usually > 5 cm


  • Morphology



    • Circumscribed


MACROSCOPIC FEATURES


General Features



  • Large, multinodular yellow mass with solid, often tangray or gray-white nonlipomatous areas


Sections to Be Submitted



  • Sections of both components must be sampled carefully


Size



  • May reach large size, especially in abdomen and retroperitoneum



MICROSCOPIC PATHOLOGY


Histologic Features



  • Abrupt or gradual transition from atypical lipomatous tumor (of any subtype) to nonlipogenic sarcoma


  • Varying size and shape of lipogenic tumor cells


  • Presence of enlarged and hyperchromatic nuclei in lipogenic component


  • Nonlipogenic sarcoma component shows broad morphologic variation


  • High-grade nonlipogenic sarcoma component (pleomorphic sarcoma, intermediate- to high-grade myxofibrosarcoma-like areas)


  • Often presence of multinucleated giant cells


  • Increased proliferative activity


  • Low-grade nonlipogenic component (uniform fibroblastic spindle cells with mild nuclear atypia)


  • Heterologous differentiation in ˜ 10% of cases

Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Dedifferentiated Liposarcoma
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