Inclusion Body Fibromatosis



Inclusion Body Fibromatosis


Elizabeth A. Montgomery, MD





Key Facts


Terminology



  • Nodular proliferation of benign fibroblastic and myofibroblastic cells with characteristic intracytoplasmic eosinophilic spherical inclusions


Clinical Issues



  • Broad-based or dome-shaped, nontender nodule over dorsal or lateral aspect of digits


  • Present in 1st 3 years of life



    • ˜ 1/3 are congenital


  • Extradigital presentation in soft tissue is rare


  • Excellent overall prognosis


  • Tendency for local recurrence (60-75% of cases)


  • No evidence of aggressive behavior, metastatic potential, or malignant transformation


  • Observation recommended in absence of deformity and impairment


Macroscopic Features



  • Nodular firm mass covered by intact skin


  • Rarely exceeds 2 cm in diameter


Microscopic Pathology



  • Sheets and fascicles of uniform myofibroblastic cells with intracytoplasmic eosinophilic spherical inclusions


  • Inclusions often perinuclear and stain bright red with Masson trichrome


  • Dense collagenous stroma


  • Overlying epidermis is often acanthotic with loss of rete ridges


Ancillary Tests



  • Masson trichrome



    • Inclusions stain bright red







Hematoxylin & eosin at medium power shows intersecting fascicles of myofibroblasts, dense extracellular collagen, and scattered intracytoplasmic eosinophilic spherical inclusions image.






Hematoxylin & eosin at high power shows plump, bland-appearing myofibroblasts with scattered intracytoplasmic eosinophilic inclusions image.


TERMINOLOGY


Synonyms



  • Infantile digital fibromatosis


  • Digital fibrous tumor of childhood


  • Infantile digital fibroma


  • Reye tumor


Definitions



  • Nodular proliferation of benign fibroblastic and myofibroblastic cells with characteristic intracytoplasmic eosinophilic spherical inclusions


CLINICAL ISSUES


Epidemiology



  • Age



    • Present in 1st 3 years of life



      • ˜ 1/3 are congenital


Site



  • Typically located over dorsal or lateral aspect of digits


  • Principle involvement of 2nd-5th digits



    • Thumb and great toe typically spared


  • Extradigital presentation in soft tissue is rare


Presentation



  • Broad-based or dome-shaped nodule


  • Nontender


  • Overlying skin is firm, stretched, and erythematous


  • Up to 2 cm in diameter


  • Functional impairment or deformity may be present


Natural History



  • 12% of cases spontaneously involute over 2-3 years


Treatment



  • Options, risks, complications



    • Observation recommended in absence of deformity and impairment



      • Spontaneous involution reported


  • Surgical approaches



    • Complete surgical excision



      • 60-75% of cases recur upon excision


      • Lower recurrence rates reported with wider surgical excisions


    • Surgical excision recommended with



      • Functional impairment


      • Continued growth


      • Cosmetic concerns


    • Removal by Mohs micrographic surgery without recurrence reported


Prognosis



  • Excellent overall prognosis


  • Tendency for local recurrence



    • 60-75% of cases


  • No evidence of



    • Aggressive behavior


    • Metastatic potential


    • Malignant transformation


MACROSCOPIC FEATURES


General Features



  • Nodular firm mass covered by intact skin


Size



  • Rarely exceeds 2 cm in diameter



    • Range of 0.3-3.5 cm reported in large series


    • Median size = 1 cm


Gross Features



  • Solid, gray-white, cut surface


  • Lacks hemorrhage


  • Lacks necrosis


Tags:
Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Inclusion Body Fibromatosis

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