Papillary microcarcinoma of the thyroid gland: is the immunohistochemical expression of cyclin D1 or galectin-3 in primary tumour an indicator of metastatic disease?

Papillary microcarcinomas (PMC) of the thyroid gland are defined according to The WHO Committee as papillary carcinomas measuring 10 mm or less in diameter. A large proportion of these tumours are found coincidentally in the treatment of symptomatic goitre and most cases follow an indolent course with an excellent prognosis. However, a more aggressive behaviour with regional and distant metastases does occur. The aim of this study was to evaluate if the immunohistochemical markers cyclin D1 or galectin-3 might indicate the presence of metastatic disease in patients with PMC at the time of diagnosis. From the 1(st) of January 1996 to 31(st) of December 2002 a total of 169 PMC patients were diagnosed and registered in the national Danish thyroid cancer database DATHYRCA and 131 of these were eligible for the study. Forty-three (33%) had histologically verified regional or distant metastases. Slides were cut from the primary tumour and immunostaining and quantification was subsequently performed. The percentage of positive cells was examined for patients with and without metastases. For cyclin D1 the median values were 31% (range: 0-59) and 21% (range: 0-75), respectively, showing a statistically significant difference (p=0.02). For galectin-3 the medians were 87% (range: 6-96) and 85% (range: 0-99) and no significant difference was found. Cyclin D1 showed significantly higher median expression in patients with metastases compared to those without, indicating a correlation to tumour aggressiveness. However, both groups showed large variation in expression, which disqualify the marker as a discriminator for the detection of metastases. Galectin-3 was without any significant correlation to the presence of metastases from PMC.