[Pathological characteristics of thyroid microcarcinoma. A review of 402 biopsies].
BACKGROUND
Thyroid microcarcinoma is a tumor of 10 mm or less, that should have a low risk of mortality. However, a subgroup of these carcinomas is as aggressive as bigger tumors.


OBJECTIVE
To describe the pathological presentation of these tumors, and compare them with larger tumors.


METHODS
All pathological samples of thyroid carcinoma that were obtained between 1992 and 2003, were studied. In all biopsies, the pathological type, tumor size, the focal or multifocal character, the presence of lymph node involvement and the presence of lymphocytic thyroiditis or thyroid hyperplasia, were recorded.


RESULTS
One hundred eighteen microcarcinomas and 284 larger tumors were studied. The mean age of patients with microcarcinoma and larger tumors was 42.7+/-14 and 49.3+/-16 years respectively (p <0,001) and 83% were female, without gender differences between tumor types. Mean size of microcarcinomas was 8.6 mm and 116 (98%) were papillary carcinomas. Of these, 109 (94%) were well differentiated and seven (6%) were moderately differentiated. Thirty six (31%) were multifocal and in 10 (8,6%), there was lymph node involvement. The mean size of larger tumors was 23.8 mm and 241 (85%) were papillary carcinomas. Of these, 200 (83%) were well differentiated, and 41 (17%) were moderately differentiated. Eighty five (35%) were multifocal and in 44 (18%) there was lymph node involvement. The prevalence of thyroiditis and hyperplasia was significantly higher among microcarcinomas than in larger tumors (15 and 2.5%, respectively, p <0.001, for the former; 32.4 and 1.7%, respectively, p <0.001, for the latter).


CONCLUSIONS
In this series, one third of microcarcinomas were multifocal and 10% had lymph node involvement. Therefore, the aggressiveness of these tumors is higher than what is reported in the literature and they should be treated with total thyroidectomy.
Fardella
Carlos
C
Departamento de Endocrinología, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago de Chile. cfardella@med.puc.cl
Jiménez
Marcela
M
González
Hernán
H
León
Augusto
A
Goñi
Ignacio
I
Cruz
Francisco
F
Solar
Antonieta
A
Torres
Javiera
J
Mosso
Lorena
L
González
Gilberto
G
Rodríguez
José Adolfo
JA
Campusano
Claudia
C
López
José Manuel
JM
Arteaga
Eugenio
E
D000328:Adult; D001706:Biopsy; D002291:Carcinoma, Papillary / Q000453:epidemiology / Q000473:pathology*; D002677:Chile / Q000453:epidemiology; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012189:Retrospective Studies; D013964:Thyroid Neoplasms / Q000453:epidemiology / Q000473:pathology*; D016896:Treatment Outcome