[586] Is Multifocality of Papillary Carcinoma of Thyroid (PTC) Explained by Intra-Thyroidal Lymphatic Metastasis?

C Singh, A Samad, JC Manivel, R Gamez, SE Pambuccian. University of Minnesota, Minneapolis, MN

Background: Papillary carcinomas of thyroid are managed by total thyroidectomy based on their high incidence of multifocality and bilaterality. Whether these multiple foci actually represent synchronous development of independent clones or represent intra-thyroidal metastatic foci from a single clone is debatable. Recent molecular studies suggest that 15-35% multifocal (MF) tumors are multi-clonal; the remainder represent a single clone. The aim of this study is to determine the frequency of intralymphatic tumor foci and the vaule of intratumoral (IT) and peritumoral (PT) lymphatic density (LD) assessment in predicting multifocality and lymph node metastases in PTC.
Design: Consecutive cases of MF and a matching number of unifocal (UF) PTC diagnosed in our institution between 2003-2009 were selected for the study. Blocks containing the interface of tumor and normal tissue were immunostained with D-2-40 (Biocare Medical) using Ventana Benchmark XT. IT and PT (within 10mm around the tumor) LD was quantified by 2 reviewers by averaging the number of lymphatics in 4 high power fields in "hot spots" identified at low power. Intralymphatic tumor (ILT) nests were also noted.
Results: PT LD was significantly higher than IT LD in both uni and multifocal PTC.

Tumor(n=61)Age-range(mean)M/FIT LD (mean+/-Std)PT LD (mean+/-Std)t(p-value)
Multifocal(n=29)10-73 (44)8/210.41+/-0.684.18+/-1.7710.28(<0.0001)
Unifocal(n=32)17-68 (44)9/230.18+/-0.392.89+/-1.2611.35(<0.0001)

IT LD did not differ between UF and MF groups (0.18±0.39, 0.41±0.68; p=0.114) or between cases with lymph node metastases (LN+) and those without (LN-). However, PT LD was higher for multifocal compared to UF PTC (2.89±1.26, 4.18±1.77; p=0.003) and between LN+ and LN- cases (p=0.05) . Four cases with ILT were identified in MF PTC.

Conclusions: We found peritumoral but not intratumoral lymphangiogenesis to correlate with both multifocality and nodal metastases in PTC. Only 4/29 cases of multifocal PTC showed intra-lymphatic tumor suggesting that plurality of tumor foci cannot be explained only on the basis of intra-lymphatic spread within thyroid.
Category: Endocrine

Monday, March 22, 2010 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 82, Monday Morning


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