Invasive breast carcinoma - IARC

A
Fig. 2.139 Multicystic peritoneal mesothelioma. A Note the multiple cysts lined by mesothelial cells within a fibrous stroma. B Irregular cysts are lined by a single
layer of cuboidal mesothelial cells.
B
dimension {1443}. The serosal surf a c e s
have an appearance indistinguishable
f rom the more common peritoneal carc i-
nomatosis or extraovarian carc i n o m a .
Histopathology
Well differentiated papillary and diffuse
malignant mesotheliomas are the most
common types. Diffuse and well differentiated
papillary mesotheliomas typically
are composed of characteristic uniform
cells with abundant eosinophilic cytoplasm.
Another variant of epithelial
mesothelioma is the deciduoid type that
simulates an exuberant ectopic decidual
reaction {2633}. Sarcomatous mesotheliomas,
including the desmoplastic type,
also occur but are relatively less common
than in the pleura {493}.
All well differentiated papillary meostheliomas
have, at least focally, a conspicuous
well developed papillary architecture
or a tubulopapillary pattern. A single
layer of uniform, cuboidal or flattened
mesothelial cells with bland nuclear feat
u res lines the papillae and tubules.
Mitoses are rare. Occasionally, mild cytological
atypia is present. Extensive fibrosis
associated with irregularity of the
glandular elements is common, and such
areas may be confused with invasive foci
of malignant mesothelioma or adenocarcinoma.
Psammoma bodies are present
in some cases.
Differential diagnosis
The most reliable indicator of malignancy
in these tumours is invasion of fat or of
organ walls; however, in small biopsies
invasion may be difficult to assess {493}.
In the peritoneal cavity entrapment of
benign cells in organizing granulation tissue
or between fat lobules is fre q u e n t
and confusing {493}.
D i ffuse peritoneal malignant mesotheliomas
may macroscopically and histologically
show a carcinomatous gro w t h
p a t t e rn and thus may be confused with
p r i m a ry peritoneal serous papillary neoplasms.
In this context immunohistochemical
detection of calretinin in the
nuclei and Ber-EP4 were the most useful
markers, whereas other mesothelial
markers had too low a sensitivity for practical
use {2113}. Well diff e rentiated papill
a ry mesothelioma lacks the stratification,
complex papillae and the mixed cell population
of low grade serous neoplasms
and lacks the stratification, cytological
atypia and mitotic figures of serous carc i-
noma. Similarly, it lacks the cytological
atypia of diffuse malignant mesothelioma
and in some instances is localized within
the peritoneum. The absence of a history
of a prior operation or reactive changes
e l s e w h e re and the formation of convincing
papillae distinguish well diff e re n t i a t e d
p a p i l l a ry mesothelioma from mesothelial
h y p e r p l a s i a .
Prognosis and predictive factors
The diffuse epithelial mesotheliomas are
typically highly aggressive; however,
unlike pleural mesotheliomas, a sizeable
number of tumours are relatively indolent
{1443}. No morphological features were
found to separate the favourable and
unfavourable group of these tumours.
The well differentiated papillary type is
often localized and has a re l a t i v e l y
favourable outcome {383,1027} compared
to the diffuse peritoneal type.
Multicystic mesothelioma
Definition
A multiloculated cystic mesothelial
tumour that typically has an indolent
course. In a few instances multiple recurrences
occur, and the disease may
progress to diffuse malignant mesothelioma
{1039}.
Synonym
Multilocular peritoneal inclusion cyst.
Epidemiology
The tumour most frequently occurs in
young to middle aged women.
Clinical findings
Patients typically present with an abdominal
or pelvic mass associated with
chronic pain. Occasional tumours are
found incidentally at laparotomy.
Aetiology
An association with asbestos exposure
has not been reported.
Macroscopy
Typically, the lesion is a large multicystic
mass that may be solitary but is more
commonly either diffuse or multifocal and
consists of multiple, translucent, grapelike
clusters of fluid filled cysts delimited
by fibrous bands. The individual cysts
are usually less than 1.0 cm in diameter
but may be up to 20 cm.
Tumour spread and staging
The tumour affects chiefly the pelvic peritoneum,
particularly the cul-de-sac,
uterus and rectum, and there may be an
198 Tumours of the ovary and peritoneum