Desmoplastic stromal reaction in papillary thyroid microcarcinoma

Aims: To evaluate the value of a desmoplastic stromal reaction (desmoplasia) as an indicator of metastasis in papillary thyroid microcarcinoma. Methods and results: One hundred and nine cases of papillary thyroid microcarcinoma from the pathological archive of the Medical University of Vienna, Austria were analysed for the presence of desmoplasia in relation to other morphological and clinicopathological parameters. Eighty-one of 109 papillary microcarcinomas showed a desmoplastic stromal reaction. The desmoplasia was significantly associated with lymph node metastases (P = 0.001) and tumour diameter (P < 0.001). In addition, 'invasive parameters', such as peritumoral and vascular invasion, were associated with the presence of a desmoplastic stromal reaction (P < 0.001 and P = 0.006, respectively), and all pT3b tumours according to the UICC classification of 2002 (i.e. with perithyroidal infiltration) showed desmoplasia. Of all morphological parameters, the best indicator of lymph node metastasis was tumour calcification (P < 0.001). Conclusions: Our data indicate that a desmoplastic stromal reaction seems to be an indicator of invasive behaviour of papillary thyroid microcarcinomas significantly associated with lymph node metastases. Papillary microtumours without signs of invasion, e.g. desmoplasia, should not be regarded as invasive carcinoma, as they are more likely to be thyroidal intraepithelial neoplasias.