Kt. Mai et al., Papillary thyroid carcinoma and related thyroid neoplastic lesions: A light microscopic study with emphasis on nuclear changes, TUMORI, 86(3), 2000, pp. 238-249
A total of 187 thyroid lesions consisting of 2 cases of Grave's disease, 21
cases of multinodular goiter, 40 follicular adenomas and 124 low-grade pap
illary thyroid carcinomas were studied to identify intermediate neoplastic
lesions in the spectrum of nuclear changes between benign reactive thyroid
follicles and low-grade thyroid papillary carcinoma. The lesions were exami
ned and classified on the basis of the following nuclear features: fine chr
omatin seen in the thyroid papillary carcinomas and coarse chromatin seen i
n follicular carcinomas. Cases with Hurthle cell changes were excluded from
the study. Cases with nuclei containing coarse chromatin were classified i
n the group of follicular adenomas with a coarse chromatin pattern. The neo
plastic thyroid lesions containing fine chromatin showed a spectrum of nucl
ear changes ranging between reactive follicular lesions and papillary thyro
id carcinoma with lymph node metastasis. Such lesions were classified as fo
llicular adenomas with a fine chromatin pattern. The nuclei of these lesion
s were graded into mild to marked "nuclear atypia with a fine chromatin pat
tern". The degree of atypia depended on the degree and extent of nuclear ch
anges. Encapsulated follicular adenomas with a fine chromatin pattern and w
ith mild atypia (11 cases), moderate atypia (13 cases), marked atypia (27 c
ases), and encapsulated or nonencapsulated papillary thyroid carcinoma were
characterized by uniform nuclei; with mild, moderate and marked nuclear at
ypia in less than 2/3 of the cell population and marked nuclear atypia in m
ore than 2/3 of the cell population; and measuring 5.4-6.3, 6.0-7.2, 6.3-9
and 7.2-10 microns in diameter, respectively, Follow-up of cases of papilla
ry thyroid carcinoma fulfilling the above criteria showed lymph node metast
asis in 33% of cases, whereas follicular adenomas with a fine chromatin pat
tern, including cases originally diagnosed as papillary carcinoma, showed n
o evidence of lymph node or distant metastasis in a follow-up period of 30
months to 15 years. In the thyroid tissue surrounding papillary thyroid car
cinoma or encapsulated follicular adenoma with a fine chromatin pattern and
marked atypla, adenomatous nodules with a fine chromatin pattern and with
low-grade nuclear atypia were identified. The adenomatous nodules with a fi
ne chromatin pattern and with mild, moderate and marked atypia showed archi
tectural, cytoplasmic and nuclear features similar to those of follicular a
denoma with a fine chromatin pattern of the same grade. Of interest, a larg
e number of cases of follicular adenoma with a fine chromatin pattern had a
reas with features of follicular adenoma with a coarse chromatin pattern.