Thyroid peroxidase immunodetection in the diagnosis of follicular variantsof thyroid papillary cancer.

Study aim: The aim of this retrospective study was to assess the role of th yroid peroxidase immunodetection in the cytological diagnosis of follicular variants of thyroid papillary cancer (FVTPC) which are difficult to identi fy by standard cytology. Patients and methods: Between 1991 and 1998, 3 505 thyroid fine needle aspi ration biopsies were performed by thyroid peroxidase immunocytochemistry an d 1 576 patients were operated on. Out of a total of 227 thyroid papillary cancers (TPC), 42 (18.5%) were diagnosed as FVTPC. The results of standard cytology and thyroid peroxidase immunodetection were compared with the hist ological findings. Results: The rate of false negatives for TPC in standard cytology was 11% ( 25/227 cases), with 40% of these false negatives being FVTPC; ten out of 42 (23.8%) cases of FVTPC were not identified by standard cytology. However, cytology with thyroid peroxidase immunodetection diagnosed 224 out of the 2 27 TPC (99%), and all the FVTPC were correctly identified (100%). Conclusions FVTCP are the most frequent source of false negatives in standa rd cytology. Thyroid peroxidase immunodetection allows most of these errors to be avoided, and correctly identifies 99% of TPC including FVTPC. (C) 20 00 Editions scientifiques et medicales Elsevier SAS.