[524] Does p53 and MIB-1 Immunostaining Help in the Diagnosis of Poorly Differentiated Thyroid Carcinoma Using the Turin Criteria?

A Martyniak, V Nose. Brigham & Women's Hospital, Boston, MA

Background: The recent Turin proposal (2007) to diagnose poorly differentiated thyroid carcinoma (PDTC) used the following criteria : presence of a solid/trabecular/insular growth pattern, absence of nuclear features of papillary thyroid carcinoma, and the presence of at least one of the following features: convoluted nuclei, mitotic activity 3 per 10 HPF, and tumor necrosis. Using these criteria, along with MIB-1 and p53 immunostaining, we attempted to validate a series of poorly differentiated thyroid tumors. Our goal is to determine if these markers can assist in further classifying these tumors, especially in cases where the proposed criteria were not met.
Design: Forty one cases of PDTC were selected and retrieved from the files at BWH over a two year period (2005-7). The cases were reviewed and the above criteria were applied. The following characteristics were analyzed: classification of the main tumor, percentage of the poorly differentiated component, mitotic rate (per 10 HPF), and the presence or absence of convoluted nuclei and necrosis. In addition, MIB-1 and p53 stains were evaluated.
Results: The average age of patients with PDTC was 56 years (range 33-83). Male and female patients were roughly present in equal proportions (20 M, 21 F). A total of 14 tumors were associated with papillary thyroid carcinoma of diverse variants, while 14 were designated pure. Six oncocytic neoplasms were present, along with one tumor arising from a follicular carcinoma. The average percentage of the poorly differentiated component was 65% (range 5-100%). Mitotic rates ranged from 0-15/10 HPF (average 2.7). Necrosis was present in 27 of 41 cases. p53 was over-expressed in 27 of 28 cases. Convoluted nuclei were seen in 27 of 41 cases. Of the remaining 14 cases without convoluted nuclei, three contained areas of necrosis, 4 contained 3 mitoses/10 HPFs, and three contained both increased mitoses and necrosis. A total of four cases lacked convoluted nuclei, increased mitoses, and necrosis, but were classified as PDTC based on increased MIB-1 staining (15%) and p53 overexpression.
Conclusions: The recently proposed Turin criteria can reliably diagnose PDTC, and should be incorporated in routine practice. Furthermore, the addition of p53 and MIB-1 stains can assist in cases where the diagnosis of PDTC is suspected based on growth pattern, but without of convoluted nuclei, increased mitoses, or necrosis. We conclude that p53 and MIB-1 stains complement and support the Turin criteria for the diagnosis of PDTC.
Category: Endocrine

Tuesday, March 10, 2009 1:00 PM

Poster Session IV # 80, Tuesday Afternoon