Desmoplastic Small Round Cell Tumor



Desmoplastic Small Round Cell Tumor


Saul Suster, MD

Elizabeth A. Montgomery, MD

Cyril Fisher, MD, DSc, FRCPath





Key Facts


Clinical Issues



  • Most common in children and young adults



    • Median age: 20 years


  • Male predilection


  • Large abdominal mass on chest x-rays and CT scans


  • Poor prognosis


  • Median survival is 24 months


Macroscopic Features



  • Large, bulky tumors (> 10 cm in greatest dimension)


Microscopic Pathology



  • Nests, trabeculae, or sheets of uniform small round cells embedded in abundant desmoplastic fibrous stroma


  • Rosette-like structures


  • Small to intermediate-sized round to oval cells with scant cytoplasm


  • High mitotic index, often with atypical (abnormal) mitoses


  • Immunohistochemically polyphenotypic


  • Vimentin, keratin, desmin, EMA, and WT1 consistently positive in tumor cells in approximately 90% of cases



    • Staining pattern for desmin and vimentin is characteristically dot-like and paranuclear


  • May also show focal positivity for CD56, NSE, chromogranin, synaptophysin, and S100 protein


  • Genetically shows t(11:22)(p13;q12), similar to Ewing sarcoma/PNET



    • Differs from Ewing sarcoma as rearranged gene on chromosome 11 is WT1 rather than FLI1






In desmoplastic small round cell tumor, islands of neoplastic cells proliferate in dense desmoplastic stroma. The tumor cells are markedly hyperchromatic in contrast to the stromal myofibroblasts image.






The neoplastic cells in desmoplastic round cell tumor are quite uniform, a feature of sarcomas with balanced reciprocal translocations. Nucleoli are inconspicuous, and cytoplasm is scanty.


TERMINOLOGY


Abbreviations



  • Desmoplastic small round cell tumor (DSRCT)


Synonyms



  • Desmoplastic small round cell tumor with divergent differentiation


  • Polyphenotypic small round cell tumor


  • Desmoplastic primitive neuroectodermal tumor


  • Intraabdominal desmoplastic small round cell tumor


Definitions



  • Primitive malignant neoplasm arising in serosal surfaces with distinctive histology composed of primitive small round blue cells embedded in abundant desmoplastic stroma


CLINICAL ISSUES


Presentation



  • Male predilection


  • Pain and weight loss


  • Most common in children and young adults (2nd or 3rd decade; median age: 20 years)


  • Most commonly present in peritoneal cavity



    • Also reported in paratesticular region, ovary, thoracic cavity, lung, central nervous system, and head and neck


Treatment



  • Surgical excision


  • Chemotherapy


Prognosis



  • Poor prognosis



    • Nearly uniformly fatal


  • Frequent local recurrence; rarely metastasizes


  • Median survival is 24 months


MACROSCOPIC FEATURES


General Features



  • Large, bulky tumors (> 10 cm in greatest dimension)


  • May also grow in multinodular fashion


  • Firm homogeneous cut surface


  • Hemorrhage and necrosis


MICROSCOPIC PATHOLOGY


Histologic Features



  • Nests, trabeculae, or sheets of small round blue cells embedded in abundant desmoplastic fibrous stroma


  • Nests may display peripheral palisading of tumor cells


  • Rosette-like structures


Cytologic Features



  • Small to intermediate-sized round to oval cells with scant cytoplasm


  • Round to oval, hyperchromatic nuclei


  • Small nucleoli


  • High mitotic rate, with typical mitoses (translocation sarcoma)

Tags:
Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Desmoplastic Small Round Cell Tumor

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