February 2018

  • Patient Information
    • 28 year old male presented with a subcutaneous mass on his forehead.
  • Clinical Diagnosis
    • Cyst
    • Lipoma
    • Spiradenoma
  • Histology

     

    Sections show a nodular subcutaneous mass composed of spindled and epithelioid cells associated with blood vessels and a myxoid stroma.

    Immunohistochemical stain for smooth muscle actin (SMA) is positive within the spindle cells.

  • Final Diagnosis

    Adult myofibroma

    • Adult myofibroma is a solitary, benign mesenchymal neoplasm that commonly presents on the head/neck region within the dermis or subcutaneous tissue.
    • Histopathology reveals a nodular, biphasic mesenchymal neoplasm composed of myofibroblasts in fascicles or whorls and collections of small, primitive cells associated with hemangiopericytoma-like blood vessels. An accompanying myxoid or chondroid stroma is also present.
    • The spindle cells express smooth muscle actin by immunohistochemistry. They are negative of desmin, EMA and S-100.
    • A related entity is infantile or multicentric myofibromatosis, which is characterized by multifocal myofibromas typically presenting during the first decade of life. Visceral involvement and spontaneous regression can be seen.
      • An autosomal dominant inheritance pattern is seen in some cases
    • Adult myofibroma, glomangiopericytoma and myopericytoma likely represent a histopathological continuum of tumors
    • Adult myofibromas are benign and excision is curative. Some lesions of adult myofibromas may spontaneously regress.
  • Summary
    • Adult myofibroma is a solitary, benign mesenchymal neoplasm that commonly presents on the head/neck region within the dermis or subcutaneous tissue
    • Histopathology reveals a nodular, biphasic mesenchymal neoplasm composed of myofibroblasts in fascicles or whorls and collections of small, primitive cells associated with hemangiopericytoma-like blood vessels. An accompanying myxoid or chondroid stroma is also present.
    • The spindle cells express smooth muscle actin by immunohistochemistry. They are negative of desmin and S-100.
    • Adult myofibromas are benign and excision is curative