Diagnostic Cytology
Fig. 13.108 Carcinoid tumor. Bronchial brushing (Papanicolaou x OI).
Fig. 13.109 Carcinoid tumor, composed of small uniform cells with
stippled chromatin arranged in nests separated by vascular connective tissue.
Pulmonary resection (H&E x MP).
be arranged in ribbons, trabeculae, rosettes, acini, or papillary
structures separated by highly vascular connective tissue septa
(Fig. 13.108). When observed in bronchial brushing specimens
and FNAs, the tumor cells occur singly as well as in sheets and
three-dimensional ball-like clusters.400,401 The cells are character-
ized by small, round-to-oval, uniform nuclei with a stippled,
granular chromatin pattern and small nucleoli (Fig. 13.109).
Cytoplasm is scant to moderate and may vary from homoge-
neous to lace-like in appearance. Necrosis is absent unless the
lesion has been traumatized or secondarily infected. Mitchell
and Parker have emphasized the presence of many capillaries.402
Peripheral carcinoids in FNA specimens may show the typical
morphology described but on occasion may exhibit a spindle
cell pattern.403-407
Renshaw and associates reviewed 1100 interpretations from
26 different cases of carcinoid tumors of the lung in FNA speci-
mens in the College of American Pathologists Non-gynecologic
Cytology Program. Twenty percent of the cases had been mis-
classified as small-cell undifferentiated carcinomas. Cellular
patterns most frequently associated with the misclassifications
included hypocellular specimens, tumor cells predominantly in
groups, and degenerated, smudgy cells.408
Fig. 13.110 Atypical carcinoid. Nests of neoplastic cells with oval nuclei
showing stippled chromatin and focal necrosis. Pulmonary resection
(H&E x MP).
When there is any question about the tumor type in routine
cytologic preparations, additional studies, such as immunoper-
oxidase stains for chromogranin or electron microscopy for doc-
umenting neurosecretory granules, may be extremely helpful.
Atypical carcinoids constitute only about 10% of all carcinoid
tumors. They may occur centrally but more commonly arise in
the periphery of the lung. Histologically, these carcinoids main-
tain the overall architecture of carcinoid tumors (Fig. 13.110),409
but cytologically they are characterized by greater cellular pleo-
morphism, nuclear hyperchromasia, mitotic figures, necrosis,
and even nuclear molding.410 Thus, the cytologic features begin
to merge imperceptibly with those of small-cell undifferenti-
ated carcinoma.411 In general, atypical carcinoids exhibit more
cytoplasm and less nuclear atypia than small-cell undifferenti-
ated carcinoma. Nevertheless, this differential diagnosis may be
exceedingly difficult or impossible in cytologic material, just as it
is in transbronchial biopsy material.409 In view of this and the fact
that atypical carcinoids are frequently respectable and associated
with a 2-year survival of greater than 50%,346 it has been suggested
that stage I small-cell tumors of the lung diagnosed by cytology or
small biopsy should be considered for resection. It has also been
proposed that the term well-differentiated neuroendocrine carci-
noma should be substituted for atypical carcinoid.412
Adenoid Cystic Carcinoma
The trachea413,414 and, less commonly, the large bronchi may
give rise to adenoid cystic carcinomas, which are identical in
appearance to those occurring in the salivary glands.415-417 These
tumors may appear as an endobronchial mass or as a circumfer-
ential area of bronchial constriction. Because these neoplasms
are covered by intact mucosa, sputum specimen findings are
usually negative. In bronchial brushings and needle aspirates,
adenoid cystic carcinoma occurs as three-dimensional clusters
of small uniform cells that surround spheric or cylindric cores of
homogeneous, hyaline, basal lamina material (Fig. 13.111). The
tumor cells, which have round-to-oval, hyperchromatic nuclei
and small nucleoli, are also found singly and in small clusters
in cytologic preparations. Patients with these neoplasms may
survive for many years, but because of the high frequency of
recurrence of this lesion, the ultimate prognosis is poor.
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