Fig. 12.3 Mesothelial hyperplasia. Papillary groups with atypia. Peritoneal
cell block washing (H&E x HP).
Fig. 12.4 Endometriosis. Papillary group with stromal cells. Peritoneal cell
block washing (H&E x HP).
Fig. 12.5 Serous borderline tumor. Papillary structure with nuclear
enlargement and crowding. Peritoneal washing (Papanicolaou x HP).
usually three-dimensional clusters of cells with coarse chroma-
tin and nuclear membrane irregularities, the N/C ratio may not
be increased if, as is sometimes the case, the cells have abun-
dant cytoplasm. In endometriosis, however, the cells are low
columnar with a bland nuclear chromatin and uniform nuclear
Peritoneal Washings and Ovary
Rupture of ovarian or adnexal cysts
often results in a distinctive
cell population that can readily be differentiated from the sur-
rounding mesothelial cells.
Paratubal cysts
have cohesive ciliated
cuboidal cells that are recognizably benign. However, washings
associated with ruptured
endometriotic cysts
may show consider-
able cytologic atypia and be difficult to differentiate from adeno-
carcinoma.15 Clinical correlation with reference to celioscopic
and histologic findings may be necessary.
Papillary Structures
The other morphologic pattern that can give rise to significant
diagnostic problems is the presence of papillary structures in
peritoneal washings. Simple papillary structures are associated
with mullerian inclusions such as
, frequently
located on the peritoneal surface of the uterus, pelvic side wall,
and cul-de-sac. These tightly cohesive tubular structures have a
scanty layer of cuboidal or short columnar cells often arranged
around psammoma bodies. The nuclear size is uniform with
a vesicular chromatin pattern, and atypia is mild with small
inconspicuous nucleoli.
These lesions need to be distinguished from
papillary carcinoma
serous borderline tumors
, which may show
both simple and complex papillary groupings as well as occa-
sional single cells. Complex papillary groups show cellular-
ity with overlapping, increased N/C ratios, increased cell size,
coarsening of the chromatin, irregular cell membranes, and
prominent nucleoli (Fig. 12.5).
Key features of papillary carcinoma
• Complex papillary groups;
• Increased cell size;
• Overlapping nuclei;
• Irregular cell membranes; and
• Prominent nucleoli.
Incidental Lesions
Unusual findings may be seen in peritoneal washings or
brushings obtained intraoperatively during cesarean section
procedure.16 Incidental findings include gestational change in
endosalpingiosis, peritoneal deciduosis, and well-differentiated
papillary mesothelioma.17 It is important to obtain relevant
clinical information and correlation with any lesions sampled
It is not uncommon for
psammoma bodies
to be identified in
benign lesions such as adenofibromas or endosalpingiosis as well
as serous papillary neoplasms. Therefore, the finding of psam-
moma bodies alone is not evidence of malignancy, even though
it would indicate that further investigation is warranted.18
Collagen balls represent nonspecific entities which appear as
globoid collagen balls or papillary clusters of mesothelial cells
with collagen cores which may raise concern for papillary neo-
Ancillary Techniques
The role of immunocytochemistry in the evaluation of patients
with malignant ascites is concerned as much with identifying
site of origin as with confirming the presence of malignancy.
Peritoneal washings or brushings are usually obtained in cir-
cumstances where the primary abdominal or pelvic lesion has
been identified, and the main concern is about diagnosis of
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