Expression of the proliferation marker Ki-67 associates with tumour staging and clinical outcome in differentiated thyroid carcinomas

Abstract

Objective: Although the prognosis of differentiated thyroid carcinoma (DTC) is excellent, with 10-year survival rates of about 90%, about one-third of patients experiences recurrent disease. We aimed to identify novel histological prognostic factors to optimize treatment and follow-up of patients at risks.

Design: Retrospective analysis of patients diagnosed from January 1990 to March 2004.

Subjects: A total of 93 patients diagnosed with DTC of which 67 with papillary and 26 with follicular histology.

Measurements: Analysis of immunohistochemical expression of somatostatin receptor (sst) subtypes 1-5, glucose transporter-1 (GLUT-1), receptor tyrosine kinase c-KIT, oestrogen and progesterone receptors, and proliferation marker Ki-67 and correlation with the patients' clinical outcome.

Results: DTC showed immunohistochemical expression of GLUT-1, C-KIT and progesterone receptor in a high percentage of cases (range: 57-80%). In contrast, the oestrogen receptor as well as the sst subtypes 1-5 was less frequently detected (range: 15-29%). Mean staining of the proliferation marker Ki-67 was 6% positive cells (range 0-20%). Ki-67 expression was significantly associated with tumour staging (ρ = 0·2076, P = 0·0459), whereas the other histopathological markers were not associated with gender, age, tumour entity, or tumour classification. Tumour staging and expression of Ki-67, oestrogen receptor and sst2, but of none of the other histopathological factors, independently predicted the clinical outcome 5 years after definitive treatment (P < 0·0001, P < 0·0001, P = 0·0004 and P = 0·0206, respectively).

Conclusions: In patients with DTC, Ki-67 expression associates with tumour staging and clinical outcome.