Eble JN, Sauter G., Epstein JI, Sesterhenn IA - iarc

Leiomyosarcoma
J. Cheville
Definition
Leiomyosarcoma is a rare malignant
mesenchymal tumour that arises from
urinary bladder smooth muscle.
ICD-O code 8890/3
Epidemiology and etiology
Although leiomyosarcoma is the most
common sarcoma of the urinary bladder it
accounts for much less than 1% of all
bladder malignancies. Males are more frequently
affected than females by over 2:1
{1639,1734,2543}. This sarcoma occurs
primarily in adults in their 6th to 8th
decade. Several cases of leiomyosarcoma
of the bladder have occurred years after
cyclophosphamide therapy {2039,2253}.
Localization
Leiomyosarcoma can occur anywhere
within the bladder, and very rarely can
involve the ureter or renal pelvis {947,
1816}.
Clinical features
The vast majority of patients present with
haematuria, and on occasion, a palpable
pelvic mass, abdominal pain or urinary
tract obstruction may be present.
Macroscopy
Leiomyosarcoma of the urinary bladder
is typically a large, infiltrating mass with a
mean size of 7 cm. High grade leiomyosarcoma
frequently exhibits gross and
microscopic necrosis.
Histopathology
Histopathologic examination reveals a
tumour composed of infiltrative interlacing
fascicles of spindle cells. Grading of
leiomyosarcoma is based on the degree
of cytologic atypia. Low grade leiomyosarcoma
exhibits mild to moderate cytologic
atypia, and has mitotic activity less
than 5 mitoses per 10 HPF. In contrast,
high grade leiomyosarcoma shows
marked cytologic atypia, and most cases
have greater than 5 mitoses per 10 HPF.
Immunohistochemically, leiomyosarcoma
stains with antibodies directed against
actin, desmin and vimentin, and are negative
for epithelial markers {1410,1639,
1734,2817}.
Leiomyoma can be morphologically separated
from leiomyosarcoma based on
its small size, low cellularity, circumscription,
and lack of cytologic atypia {1639}.
Reactive spindle cell proliferations such
as inflammatory pseudotumour or postoperative
spindle cell nodule/tumour can
be difficult to distinguish from leiomyosarcoma
{1572,2889}. Leiomyosarcoma
exhibits greater cytologic atypia, abnormal
mitoses, and an arrangement in
compact cellular fascicles in contrast to
reactive spindle cell proliferations, which
have a loose vascular myxoid background.
However, myxoid change can
occur in leiomyosarcoma {2899}.
Sarcomatoid carcinoma can resemble
leiomyosarcoma but is usually associated
with a malignant epithelial component
or exhibits cytokeratin positivity.
Prognosis
Although previous reports suggest that
5-year survival after partial or radical cystectomy
approaches 70%, the largest
recent study indicates that 70% of
patients with leiomyosarcoma developed
recurrent or metastatic disease, resulting
in death in nearly half {1639}.
Fig. 2.75 Leiomyosarcoma of the bladder.
Fig. 2.76 Bladder leiomyosarcoma.
140 Tumours of the urinary system