Distinguishing small cell carcinoma from non-small cell carcinoma of
the lung: correlating cytologic features and performance in the
College of American Pathologists Non-Gynecologic Cytology Program.
Arch
Pathol Lab Med. 2005 May;129(5):619-23.
CONTEXT: The
cytologic features of small cell carcinoma of the lung are well
described. Nevertheless, some small cell carcinomas may be difficult
to reproducibly distinguish from non-small cell carcinomas, and this
distinction carries significant clinical importance.OBJECTIVE: To
correlate the cytologic features of individual cases of small cell
carcinoma of the lung in fine-needle aspiration specimens from the
College of American Pathologists Non-Gynecologic Peer Comparison
Cytology Program with the frequency of misclassification as non- small
cell carcinoma. DESIGN: We reviewed 1185 interpretations of 23
different cases of small cell carcinoma in lung fine-needle aspiration
specimens and correlated the cytologic features noted in these cases
with performance in the program. RESULTS: Cases were divided into
those that were frequently misclassified as non-small cell carcinoma
(at least 10% of the responses, 11 cases) and those that were
infrequently misclassified as non-small cell carcinoma (<5% of all
responses, 12 cases). All cases had areas on the slides with classic
features of small cell carcinoma. However, 10 of 11 cases that were
frequently misclassified as non-small cell carcinoma had cells with
either increased cytoplasm (4 cases), cytoplasmic globules (so-called
paranuclear blue bodies) (3 cases), or apparent intracytoplasmic
lumina (3 cases). These features were not identified in cases that
were infrequently misclassified (P = .005). In addition, cases more
frequently misclassified as non-small cell carcinoma tended to show
better overall cellular and group preservation. CONCLUSIONS: Frequent
misclassification of small cell carcinoma as non-small cell carcinoma
in lung fine-needle aspiration specimens in this program correlates
strongly with the presence of cytoplasmic features that may suggest
non-small cell carcinoma or with the presence of paranuclear blue
bodies. Misclassification in this program may reflect a variety of
factors, including the variation in the cytologic features of
individual cases, but also the lack of wide recognition that some
features of non-small cell carcinoma may also be noted in
well-preserved cases of small cell carcinoma.
Distinguishing
carcinoid tumor from small cell carcinoma of the lung: correlating
cytologic features and performance in the College of American
Pathologists Non-Gynecologic Cytology Program.Arch
Pathol Lab Med. 2005 May;129(5):614-8.
CONTEXT: The
cytologic features of carcinoid tumor of the lung are well described.
Nevertheless, some carcinoids may be difficult to distinguish from
small cell carcinomas. OBJECTIVE: To correlate the cytologic features
of individual cases of carcinoid tumor of the lung in fine-needle
aspiration specimens in the College of American Pathologists
Non-Gynecologic Cytology Program with the frequency of
misclassification as small cell carcinoma. DESIGN: We reviewed 1100
interpretations from 26 different cases of carcinoid tumor in lung
fine-needle aspiration specimens in the College of American
Pathologists Non-Gynecologic Cytology Program and correlated the
cytologic features with the performance in the program. RESULTS: Cases
were divided into those that were frequently misclassified as small
cell carcinoma (at least 20% of the responses, 19 cases) and those
that were infrequently misclassified as small cell carcinoma (<10% of
all responses, 7 cases). All cases had areas with classic features of
carcinoid tumor. Cases were reviewed independently by 3
cytopathologists specifically looking for cytologic features that
might be responsible for misclassification as small cell carcinoma.
All 7 cases that were infrequently misclassified consisted of numerous
monotonous well-preserved tumor cells that were either entirely round
or were a mixture of round and spindle-shaped cells. Six of 7 cases
showed a prominent streaming vascular pattern with tumor cells
attached to the endothelial cell core. In contrast, cases that were
frequently misclassified had 1 of 6 patterns that were not seen in
cases that were rarely misclassified. These 6 patterns were: (1)
poorly preserved and pale-staining cells with fine chromatin and a
suggestion of molding (5 cases); (2) numerous large, well-preserved,
spindle-shaped cells (2 cases); (3) numerous cells varying markedly in
both size and shape (both round and spindle-shaped cells), with a
common finding of degenerated, smudgy, small round and spindle-shaped
cells (9 cases); (4) hypocellular specimens (8 cases); (5) obscuration
of cells by blood (2 cases); and (6) tumor cells present predominantly
in groups, with few isolated cells (8 cases). In none of these cases
were mitoses or true necrosis identified. CONCLUSIONS: Frequent
misclassification of carcinoid tumor as small cell carcinoma in lung
fine-needle aspiration specimens in this program correlates strongly
with specific cytologic features, some of which are common in small
cell carcinoma (fine chromatin, molding, smudgy chromatin) and others
that are not (spindle-shaped cells). In addition, hypocellular
specimens or specimens with cellular obscuration performed poorly,
along with specimens exhibiting absence of the commonly described
carcinoid feature of streaming vascularity. Awareness of these
patterns may aid in avoiding misdiagnosis.
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