Angiomatoid Fibrous Histiocytoma



Angiomatoid Fibrous Histiocytoma


Khin Thway, BSc, MBBS, FRCPath





Key Facts


Terminology



  • Rare neoplasm of intermediate biologic potential


  • Most often arises in extremities of children and young adults


  • Histologically often confused with both benign and malignant lesions


  • 3 characteristic translocations



    • 2 identical to those of clear cell sarcoma


Clinical Issues



  • Slowly growing


  • Mostly indolent


  • 15% recur


  • 1% metastasize


Microscopic Pathology



  • Fibrous and lymphoplasmacytic cuff



    • Germinal centers


  • Sheets of histiocyte-like and spindle cells


  • Blood-filled spaces


Ancillary Tests



  • Desmin positivity in 1/2 of cases


  • Specific translocations


Top Differential Diagnoses



  • Pleomorphic sarcoma (malignant fibrous histiocytoma)


  • Aneurysmal benign fibrous histiocytoma


  • Palisaded (intranodal) myofibroblastoma


  • Kaposi sarcoma


Diagnostic Checklist



  • Age distribution






Hematoxylin & eosin shows a circumscribed lesion with a pronounced lymphoid cuff, including prominent germinal centers. This appearance may mimic that of a tumor metastatic to a lymph node.






Hematoxylin & eosin shows cellular proliferations of spindle cells in loose fascicles and areas image with a storiform pattern. The cells have bland ovoid nuclei in this angiomatoid fibrous histiocytoma.


TERMINOLOGY


Abbreviations



  • Angiomatoid fibrous histiocytoma (AFH)


Synonyms



  • Originally angiomatoid “malignant” fibrous histiocytoma



    • Term “malignant” removed due to indolent behavior


    • Unrelated to malignant fibrous histiocytoma (MFH)/pleomorphic sarcoma group of neoplasms


Definitions



  • Rare neoplasm of intermediate biologic potential with 3 characteristic translocations


ETIOLOGY/PATHOGENESIS


Lineage Unknown



  • Endothelial or histiocytic differentiation not proven


  • Desmin expression suggests myoid or myofibroblastic differentiation


  • Postulated nodal fibroblastic reticulum cell differentiation


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Rare


    • Accounts for approximately 0.3% of all soft tissue neoplasms


  • Age



    • Infancy to 8th decade


    • Predominantly in children and young adults


  • Gender



    • Slight female predilection


Site



  • Extremities


  • Trunk


  • Head and neck


  • 1 primary intracerebral case reported


  • Usually superficial



    • Deep dermis and subcutis


  • Few arise deeply


Presentation



  • Slowly growing, painless mass



    • Usually small



      • Most often 2-4 cm


  • Constitutional symptoms in subset



    • e.g., malaise, pyrexia, and anemia


    • Possible tumoral cytokine production


Treatment



  • Surgical approaches



    • Wide excision



      • Usually curative


    • Radiotherapy and chemotherapy



      • For rare metastatic or unresectable tumors


Prognosis



  • Excellent in most cases



    • Majority of lesions indolent


  • Regional recurrence rate up to 15%


  • Metastasis rate of approximately 1%



    • Rare cause of death


  • No firm morphologic or clinical indicators of behavior



    • Infiltrative margin and deep location can predict recurrence


MACROSCOPIC FEATURES


General Features



  • Firm


  • Circumscribed


  • Blood-filled cystic cavities



Sections to Be Submitted



  • Lesion should be thoroughly sampled



    • Features, such as lymphoid cuff, may only be present focally


  • Small lesions should be submitted in entirety


MICROSCOPIC PATHOLOGY


Histologic Features



  • Circumscribed


  • Lobulated


  • Fibrous pseudocapsule



    • Dense peripheral lymphoplasmacytic cuff in up to 80%


  • Cellular tumor



    • Cells with bland, vesicular, ovoid to spindled nuclei


    • Sheets


    • Short fascicles


    • Occasional storiform patterns


    • Ovoid or spindle forms may predominate


    • Mitoses infrequent


  • Hemorrhagic cavities



    • No endothelial lining


  • Some show marked pleomorphism and mitotic activity


  • Giant cells in some cases


Predominant Pattern/Injury Type



  • Circumscribed


  • Cystic, macroscopic


Predominant Cell/Compartment Type



  • Mesenchymal


ANCILLARY TESTS


Immunohistochemistry



  • Desmin positivity



    • Approximately half of cases


    • Strong cytoplasmic expression


    • Scattered desmin(+) cells may be present within lymphoid proliferation


    • Tumors negative for skeletal muscle markers



      • e.g., myogenin and MYOD1


  • Epithelial membrane antigen (EMA)



    • Just under half of cases


  • CD68



    • Frequent but nonspecific


  • CD99



    • Frequent but nonspecific


  • Very occasional “intermediate” CD34 expression reported



    • Usually negative


    • Other vascular endothelial markers also usually absent


Cytogenetics

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Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Angiomatoid Fibrous Histiocytoma

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