Low-Grade Fibromyxoid Sarcoma (Evans Tumor)



Low-Grade Fibromyxoid Sarcoma (Evans Tumor)


Khin Thway, BSc, MBBS, FRCPath





Key Facts


Terminology



  • Malignant fibroblastic neoplasm composed of bland spindle cells in collagenous matrix, often with prominent collagenous nodules


  • Characterized by specific translocations producing fusion oncogenes


Clinical Issues



  • Adults (typically in 4th decade)


  • Mainly deep-seated, but can also occur superficially in dermis and subcutis


  • Proximal extremities (especially lower limbs) and trunk; rarely other sites


  • Recurrence rates of up to 21%


  • Recurrence lower in superficial cases


  • Metastatic rate of approximately 30% in genetically confirmed cases


Microscopic Pathology



  • Whorled distributions of bland fibroblasts


  • Collagenous or myxoid matrix, often in distinct zones


  • Owing to bland morphology, tumors often mistaken for variety of benign or low-grade neoplasms


Ancillary Tests



  • MUC4 immunohistochemistry is sensitive and specific


  • CD34 positivity in some cases


  • Occasional EMA and claudin-1 positivity, which can make distinction from perineurioma difficult


  • Balanced translocations


  • t(7;16)(q32-34;p11) FUS, CREB3L2


  • t(11;16)(p11;p11) FUS, CREB3L1







Low-grade fibromyxoid sarcoma (LGFMS) (hematoxylin & eosin) shows the interface between the myxoid areas image and the collagenous areas image of the tumor.






LGFMS displays a giant rosette composed of sparsely cellular collagenous tissue cuffed by a markedly cellular distribution of bland tumor cells image.


TERMINOLOGY


Abbreviations



  • Low-grade fibromyxoid sarcoma (LGFMS)


Synonyms



  • Fibrosarcoma, fibromyxoid type; hyalinizing spindle cell tumor with giant rosettes


Definitions



  • Malignant fibroblastic neoplasm composed of bland spindle cells in collagenous and myxoid matrix, often with prominent collagenous nodules


  • Characterized by specific translocations producing fusion oncogenes


  • Despite histologically low-grade morphology, up to 30% can metastasize


ETIOLOGY/PATHOGENESIS


Characteristic Translocations



  • Produce chimeric fusion genes


  • Cellular origin still unknown, but mesenchymal neoplasm with fibroblastic-like cells


CLINICAL ISSUES


Epidemiology



  • Incidence



    • True incidence unknown


    • Tumor probably underreported in literature due to its morphologic resemblance to other benign and malignant tumors


  • Age



    • Adults (typically in 4th decade), but wide age distribution



      • Significant proportion in patients < 18 years old


  • Gender



    • M > F


Site



  • Mainly deep-seated, but a smaller proportion occurs in dermis and subcutis


  • Proximal extremities (especially lower limbs) and trunk; rarely other sites including viscera


  • Superficial lesions have higher incidence in childhood


Presentation



  • Painless mass



    • Many are of long duration


Treatment



  • Surgical approaches



    • Wide excision


    • Long-term follow-up is mandatory, in view of potential for late metastases


Prognosis



  • Recurrence rates of up to 21%



    • Recurrence is lower in superficial cases


  • Metastatic rate of approximately 30% in genetically confirmed cases



    • > 80% of metastases appeared after 9 years


    • No reported metastases in superficial tumors


MACROSCOPIC FEATURES


General Features



  • Well-defined mass


  • White cut surface, often with glistening myxoid areas


  • Sometimes cystic foci, but necrosis rare


MICROSCOPIC PATHOLOGY


Histologic Features

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Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Low-Grade Fibromyxoid Sarcoma (Evans Tumor)

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