Thyroid neoplasms represent a broad spectrum of tumors with different
biologic behaviors, The majority of these tumors can be readily diagno
sed by characteristic histopathologic features, but the distinction be
tween follicular adenomas and follicular carcinomas can be difficult,
Recent studies with cell cycle proteins such as p27(kip1) (p27), a cel
l cycle inhibitory protein, and Ki-67, a proliferation marker, suggest
that these markers might be useful in predicting the behavior of vari
ous neoplasms, We analyzed 95 thyroid lesions (16 follicular adenomas,
23 follicular carcinomas, 22 papillary carcinomas, 27 anaplastic carc
inomas, plus 7 non-neoplastic thyroids [NNTs], used as a control group
) for expression of p27 and Ki-67 by immunostaining. The distribution
of immunoreactivity was analyzed by quantifying nuclear staining in ea
ch case without knowledge of the diagnosis or outcome, Clinical histor
y and follow-up information were obtained by chart review. There were
significant differences in the expression of p27 between follicular ad
enomas (labeling index [LI] = 47.9 +/- 5.6) and follicular carcinomas
(LI = 15.7 +/- 2.0), Papillary carcinomas (LI = 11.6 +/- 3.0) and anap
lastic carcinomas (LI = 9.4 +/- 1.7) had p27 LIs similar to that of fo
llicular carcinomas; the NNT group had the highest p27 LI (74.1 +/- 4.
9). The Ki-67 LI of anaplastic carcinomas (57.6 +/- 3.8) was more than
threefold greater than that of any other group, Logistic regression s
howed that p27 was effective in distinguishing follicular adenomas fro
m follicular carcinomas (P = .0056) and that Ki-67 could also distingu
ish follicular adenomas from follicular carcinomas (P = .0060). Analys
is of follicular carcinomas with and without metastases showed signifi
cantly higher expression of Ki-67 in patients with metastases (P = .00
19), These results indicate that antibodies to p27 and Ki-67 might be
useful in distinguishing between thyroid neoplasms that are difficult
to diagnose by the usual histopathologic criteria.