PSEUDOSARCOMATOUS MYOFIBROBLASTIC TUMOR OF THE URINARY-BLADDER IN CHILDREN - A STUDY OF 11 CASES WITH REVIEW OF THE LITERATURE - AN INTERGROUP RHABDOMYOSARCOMA STUDY
H. Hojo et al., PSEUDOSARCOMATOUS MYOFIBROBLASTIC TUMOR OF THE URINARY-BLADDER IN CHILDREN - A STUDY OF 11 CASES WITH REVIEW OF THE LITERATURE - AN INTERGROUP RHABDOMYOSARCOMA STUDY, The American journal of surgical pathology, 19(11), 1995, pp. 1224-1236
Pseudosarcomatous myofibroblastic tumor (PMT) is the result of reactiv
e proliferation of myofibroblasts. In children, PMT of the urinary bla
dder can be mistaken for embryonal rhabdomyosarcoma clinically, radiol
ogically, and by light microscopy. We are reporting the clinical, hist
ological, and immunohistological features of 11 patients with childhoo
d PMT of urinary bladder that were diagnosed initially as a sarcoma, u
sually rhabdomyosarcoma. The morphologic spectrum of PMT is broad, wit
h mixtures of myxoid, leiomyomatous, and sclerosing matrix patterns, t
he myxoid type being the most common. The proliferating cells consist
of three forms of myofibroblastic cells: long spindle cells (type I),
intermediate spindle cells (type II), and ganglion-like cells (type II
I), together with various types of inflammatory cells. The immunohisto
logic profile of the proliferating cells was characterized by positive
reactions to vimentin, muscle-specific actin, ct-smooth-muscle actin,
polyclonal desmin, and keratin. Ultrastructural studies showed myofib
roblastic differentiation of the tumor cells. No patients have had met
astases or local recurrence. Histologic, immunohistochemical, and clin
ical data from 71 cases of PMT, including the 11 cases in this report,
confirm the benign behavior of these lesions. The etiology of these l
esions is unclear, including the absence of surgical or other trauma i
n all of the children.