Sabato 27 ottobre 2012 - Pacini Editore

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Fig. 1. Gross appearance of the Wdpm: a whitish rough plaque with
papillae easily detectable on cut surface.
within the opened specimen. Histological examination showed a
chronic follicular cholecystitis. Aspecific findings suggestive for
prior surgical abdominal interventions, such as numerous foamy
histiocytes (CD68+), steatonecrosis, fibrosis and mild chronic inflammation
were noted on the epiploic appendix and on the hard
fibrous nodule containing the Prolene implant, the latter probably
representing a hernioplastic plug migrated from the inguinal canal
and endoved within the abdominal cavity. Microscopic examination
of the omental peritoneal lesion showed a papillary proliferation
consisting of thick prominent sclerohyaline cores lined by a
single row of bland cuboidal mesothelial cells. Immunoperoxydase
studies demonstrated that the lining cells were positive for
CK 5/6 and calretinin, thus confirming their mesothelial nature
(Fig. 2). No mitotic activity, multistratification or significative
cytological atypia were present. Electron microscopic examination
further confirmed the mesothelial nature of the cells lining
the papillary proliferation and their bland cytological ultrastructural
features consisting of microvilli, rough endoplasmic reticulum,
microfilaments, and desmosomes (Fig. 3), in keeping with
previously reported findings 1 . According to the aforementioned
histological, immunohistochemical and ultrastructural features, a
diagnosis of WDPM was made.
In consideration of the substantial benignity of this entity, as
reported in the literature, in contrast to malignant mesothelioma
Fig. 2. Histological features of the lesion, consisting of thick, sclerotic
papillae lined by a single row of non atypical mesothelial cells. a. low
magnification (2x, H&E); B. detail of the papillae with a thick fibrovascular
cores (10x, H&E); C. positive immunohistochemical staining for
Calretinin; d. positive immunohistochemical staining for Ck5/6.
CONGRESSO aNNualE di aNatOmia patOlOGiCa SiapEC – iap • fiRENzE, 25-27 OttOBRE 2012
Fig. 3. ultrastructural features of the mesothelial cells lining the papillae.
a. Whole mount image of an entire cell; B. Rough endoplasmic
reticulum and microfilaments. c. Microvilli and desmosomes.
that notoriously carries a very poor prognosis, the patient was assigned
to a “watchful waiting” strategy, without further surgical
or farmacological treatment. A subsequent TC exam, performed
3 months after the surgical intervention, showed no parenchymal
lesions suspicious for disease progression and/or extension in
both thoracic and abdominopelvic scans. Currently the patient is
still in a follow-up regime.
Discussion. WDPM is a relatively rare serosal lesion usually affecting
individuals with no history of asbestos exposure, mostly
women of reproductive age 2 3 , the omental and pelvic peritoneum
being the most typical involved areas, and less commonly
seen at different sites such as pleura 4 5 , pericardium 6 and tunica
vaginalis 7-10 . Grossly, WDPMs are mostly solitary but can be
multiple, and appear as gray to white, firm, papillary or nodular
lesions generally measuring less than 2 cm in diameter, even if
larger WDPMs (up to 6 cm) have been previously reported 1 2 .
WDPM must be differentiated at one end of the spectrum from
mesothelial hyperplastic proliferations and, at the other end,
from malignant mesothelioma. In mesothelial hyperplasia, that
not infrequently is characterized by a papillary architecture,
the papillae have a very thin fibrous core if any, being in most
cases composed exclusively of mesothelial cells organized in a
pseudopapillary fashion. Moreover, a reactive flogistic process
of moderate grade at least, is invariably seen in the adjacent serosa
3 ; this is an uncommon finding in WDPMs. The differential
diagnosis of malignant mesothelioma (MM) and WDPM can be,
at times, very problematic, especially in bioptic material or in
areas of malignant mesothelioma resembling WDPM. Thorough
examination of the specimen, given that the material submitted
for histological examination is representative of the entire
lesion, should lead to the correct diagnosis in most instances.
Their clinical and biological behavior is almost invariably benign
and indolent, even though some have been reported as persistent,
recurrent or even associated with an aggressive course
or progression to MM 4 11 . The majority of such cases however
might well represent undersampled malignant mesotheliomas
from the beginning. In cases with poorer prognosis, overtreatment
(adjuvant chemotherapy) may have been the main cause
of morbidity and mortality associated with WDPMs 2 . It is very
important to be aware of this pathologic entity, which occurs
rarely and most commonly as an incidental finding. Accuracy
and thorough examination is mandatory in order to exclude a
malignant mesothelioma, which could manifest its invasivity
and cytologic atypia only in focal areas. At the same time, it
is necessary to be aware of the indolent biological behavior of
WDPMs, when correctly diagnosed, in order to prevent overtreatment.