Pleural, Peritoneal, and Pericardial Effusions
Fig. 19.102 Smear of pleural effusion depicting mesothelioma cells
with their typical intercellular articulation, including the clasping type of
articulation. Reproduced with permission from Naylor B: The exfoliative
cytology of diffuse malignant mesothelioma.
J Pathol Bacteriol
Fig. 19.103 Smear of pleural effusion depicting a pair of mesothelioma
cells with one exhibiting marked cytoplasmic vacuolation (Papanicolaou x
HP). Reproduced with permission from Naylor B: The exfoliative cytology of
diffuse malignant mesothelioma.
J Pathol Bacteriol
to the diagnosis of mesothelioma are the following: the large
number of cells, the numerous clusters of cells, the increased
size of the cells, and the prominence of their nucleoli. These
and other morphologic differences between benign mesothelial
and mesothelioma cells have been corroborated in a quantita-
tive morphologic study by Kwee and co-workers.204 Vacuolated
mesothelioma cells may be seen, but in all other respects they
resemble the nonvacuolated mesothelioma cells that accom-
pany them (Fig. 19.103).203,205
M orphologic Variants
Apart from the "standard" cytologic features of diffuse malig-
nant mesothelioma described previously, various other mor-
phologic features have been emphasized. For example, Whitaker
and Delahaye and colleagues pointed out the high frequency
of a central core of collagen within aggregates of mesothelioma
cells in cell blocks (Fig. 19.104), much higher than in aggregates
Fig. 19.104 Cell block of pleural effusion depicting papillary fragments of
diffuse malignant mesothelioma of epithelial type. Note the collagenous
cores of the papillary fragments (H&E x LP). Reproduced with permission
from Kim K, Naylor B:
Practical Guide to Surgical Pathology with Cytologic
New York: Springer-Verlag; 1992.
of metastatic adenocarcinoma cells.173,176 However, this phe-
nomenon is not confined to malignant mesothelial cells; it has
also been demonstrated in clusters of spontaneously exfoliated
benign mesothelial cells and is frequently seen in smears and
cell blocks of peritoneal washings.23-25,206
Highly vacuolated or ballooned forms of mesothelioma cells
have been described.203,205,207,208 Some vacuolated mesothelioma
cells may be observed in almost every cytologic preparation of
mesothelioma; however, we have not seen an example in which
a high proportion or almost all of the cells are highly vacu-
olated, as described by Spriggs and Grunze.205 This type of vacu-
olation is quite different from the tiny, diffuse, lipid-containing
cytoplasmic vacuoles found in the cells of some mesotheliomas,
best demonstrated in stained wet films and in air-dried smears
stained with one of the Romanowsky stains.
Psammoma bodies are occasionally found within the cores
of fragments of mesothelioma; they have no diagnostic value
and are regarded as a nonspecific phenomenon that may occur
in almost any papillary neoplasm.
Mesothelioma cells often contain large amounts of glycogen.
The glycogen is sometimes randomly dispersed throughout the
cytoplasm, but it is often present as large, crescent-shaped lakes
in a perinuclear position. In Papanicolaou-stained smears, this
appears as yellow material (Fig. 19.105) like that seen in glyco-
genated squamous epithelial cells in cervical smears.
Effusions of diffuse malignant mesothelioma are likely to
contain a high concentrate of hyaluronic acid which may be
manifested by increased viscosity of the effusion, detectable
by the naked eye.4,209,210 In Papanicolaou-stained smears this
phenomenon may be manifested by the following:
1. A diffuse pink or pale blue background (Fig. 19.106);
2. Widespread blue-gray background particles
(Fig. 19.107); or
3. Similar particles in acinar spaces formed by the
neoplasm (Fig. 19.108).
Mesothelioma cells in an effusion may undergo degen-
eration. When this happens many of the degenerated cells
acquire, apart from nuclear changes, eosinophilic cytoplasm
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