Myofibroblastoma of the tunica testis: evolving phase of so-called fibrous pseudotumor?

A collagen-rich stromal tumor attached to the testicular tunica albuginea of a 22-year-old male is reported. Immunocytochemical and ultrastructural characterization revealed a predominant population of myofibroblasts, an as yet unrecognized observation in tumors arising from testicular tunics. The possible relationship with so-called fibrous pseudotumor (nodular fibrous proliferation) is discussed. The myofibroblastic nature of the cell population would support the hypothesis of a reactive contractile process if one accepts this tumor as an evolving phase of fibrous pseudotumor.