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


Clinical Issues



  • Slowly growing


  • Mostly indolent


  • 15% recur, 1% metastasize


Microscopic Pathology



  • Fibrous and lymphoplasmacytic cuff



    • Dense peripheral lymphoplasmacytic cuff in up to 80%


  • Histiocyte-like and spindle cells



    • In sheets, short fascicles, occasional storiform distributions


  • Cells with bland, vesicular, ovoid to spindled nuclei


  • Blood-filled spaces


  • Some show marked pleomorphism and mitotic activity


Ancillary Tests



  • Desmin positivity in 1/2 of cases


  • Specific translocations


Top Differential Diagnoses



  • Aneurysmal benign fibrous histiocytoma


  • Spindle cell hemangioma


  • Kaposi sarcoma


  • Pleomorphic sarcoma (MFH)







Angiomatoid fibrous histiocytoma is 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.






The tumor is composed of a cellular proliferation of spindle cells in loose fascicles and other areas image with a storiform pattern. The cells have relatively bland ovoid nuclei.


TERMINOLOGY


Abbreviations



  • Angiomatoid fibrous histiocytoma (AFH)


Synonyms



  • Originally termed “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



  • Desmin expression



    • Suggests myoid or myofibroblastic differentiation


  • Endothelial or histiocytic differentiation unlikely


  • 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


  • Very rarely other sites



    • Lung, mediastinum, retroperitoneum, ovary, vulva


  • 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



    • Malaise


    • Pyrexia


    • Anemia


    • Due to 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%


  • 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


  • Small lesions should be submitted in entirety


MICROSCOPIC PATHOLOGY


Histologic Features



  • Circumscribed, lobulated mass


  • Fibrous pseudocapsule



    • Dense peripheral lymphoplasmacytic cuff



      • Present in up to 80%


      • Mixture of B- and T cells


      • Germinal center formation may be present


  • Cells with bland, vesicular, ovoid to spindled nuclei



    • Sheets


    • Short fascicles


    • Occasional storiform patterns


    • Ovoid or spindle forms may predominate


    • Mitoses infrequent


  • Hemorrhagic cavities



    • Lack endothelial lining


  • Some show marked pleomorphism and mitotic activity



    • Not shown to be associated with outcome


  • Giant cells in some cases


  • Clear cells and reticular and pulmonary edema-like patterns are rarely described


Predominant Pattern/Injury Type



  • Circumscribed


  • Cystic, macroscopic


Predominant Cell/Compartment Type



  • Mesenchymal


ANCILLARY TESTS


Cytogenetics



  • 3 characteristic translocations identified



    • (2;22)(q33;q12) EWSR1-CREB1



      • Most common gene fusion


    • (12;16)(q13;p11) FUS-ATF1


    • (12;22)(q13;q12) EWSR1-ATF1


    • Fusion type not thought to be related to tumor site


  • No correlation between type of fusion gene and clinicopathologic features


  • All these translocations also seen in clear cell sarcomas



    • Clear cell sarcoma (of tendons and aponeuroses)


    • Clear cell sarcoma-like tumor of the gastrointestinal tract


    • Morphologically and clinically distinct neoplasms


In Situ Hybridization



  • Translocated chromosomes can be identified by FISH


PCR



  • Fusion gene transcripts can be identified by RT-PCR



    • Frozen or paraffin-embedded material


Electron Microscopy



  • No diagnostic ultrastructural findings


DIFFERENTIAL DIAGNOSIS


Aneurysmal Dermatofibroma (Benign Fibrous Histiocytoma)

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Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Angiomatoid Fibrous Histiocytoma

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