Re-evaluation of MIB-1 immunostaining for diagnosing hyalinizing trabecular tumour of the thyroid: semi-automated techniques with manual antigen retrieval are more accurate than fully automated techniques

Abstract

Abstract. Hyalinizing trabecular tumour (HTT) immunohistochemically shows cell membranous immunoreactivity for MIB-1. This aberrant immunoreactivity is an important factor for the diagnosis of HTT. However, fully automated stainers frequently fail to confirm the immunoreactivity. The aim of this study is to investigate the cause of false negative cell membranous immunoreactivity for MIB-1 in HTT using fully automated stainers, to determine potential reasons for the problem, and to establish methods confirming cell membranous immunoreactivity for MIB-1 in HTT. Six participating institutions examined immunoreactivity for MIB-1 in 10 HTT cases using two approaches: fully automated and semiautomated methods. In the latter, antigen retrieval was carried out using manual methods adopted for routine assays at each institute. The autostainers used included the BOND-MAX, BOND-III, Benchmark XT, and Omnis systems. Using fully automated methods, institute E showed cell membranous MIB-1 positivity in all HTT cases. In contrast, at institute D, all HTT cases were negative. The positive rates of the remaining four institutes ranged from 10% to 20%. The incidence of positive cases using semi-automated methods was 100%, 90%, 90%, 30%, 80%, and 100% at institutes A, B, C, D, E, and F, respectively. We assert that antigen retrieval should be conducted manually for diagnosis of HTT; furthermore, definitively diagnosed HTT should be prepared as the external positive control.

A large series of hyalinizing trabecular tumors: Cytomorphology and ancillary techniques on fine needle aspiration

“…Immunohistochemistry can assist in diagnosing HTT, even though some of the biomarkers employed may not show significant specificity . In keeping with the follicular cell origin of HTT, different authors, including our group, have used HBME‐1 and galectin‐3 .…”

“…Although not used in our study, mostly due to the difficulties in recognizing the cytological features of HTT, numerous papers have concluded that MIB‐1 is also a useful diagnostic tool in cytological samples . HTT shows a distinctive membrane and cytoplasmic positivity for Ki‐67 (using the clone MIB‐1) when the reaction is performed at room temperature …”

“…The cytological application of ancillary techniques, including immunocytochemistry (ICC) and molecular testing, might represent a valid method for those cases with a suspicion of HTT . From a molecular point of view, HTT harbors RET/PTC rearrangements in up to 45% of cases, whereas wild‐type RAS and wild‐type BRAF have been reported in all published series. However, BRAF mutations are only found in approximately 45% of PTCs; therefore, although the presence of a BRAF V600E mutation would rule out a HTT diagnosis, a wild‐type result cannot exclude a diagnosis of HTT .…”

Hyalinizing Trabecular Tumor of the Thyroid Gland, a Diagnostic Challenge in Fine-Needle Aspiration Cytology: Case Report

“…HTT does not show BRAF (V600E) mutation [ 9 ]. HTT has a unique immunohistochemical staining pattern for Ki-67 MIB1 monoclonal antibody, which is positive in peripheral tumor cell cytoplasm but expressed in the nuclei of most other tumors [ 2 , 10 ].…”

“…However, immunohistochemistry and mutation tests are difficult to perform on cytology specimen and are not sufficient to rule out PTC and diagnose HTT on FNA. General use of Ki-67 staining in HTT FNA specimens is also expensive; therefore, Ki-67 staining should be limited to carefully selected inconclusive cases, for example those cases showing nuclear features of PTC but with sparse hyaline material [ 2 , 10 , 11 ].…”