[1315] Topographic Distribution of PTC by Mapping in Coronal Sections of Thyroidectomy Specimens

Kona Williams, Previn Gulavita, Bibianna Purgina, Chi Lai, Bernhard Olberg, Kien T Mai. Ottawa Hospital and the University of Ottawa, Ottawa, ON, Canada

Background: Papillary thyroid carcinoma (PTC) is commonly a multifocal and bilateral disease with significant potential for lymph node metastasis. Mapping of PTC foci has not been studied. The purpose of this study is to map PTC foci in coronally-sectioned thyroidectomy specimens.
Design: One hundred consecutive thyroid specimens (thyroidectomy or lobectomy followed by completion thyroidectomy) were sectioned in the coronal plane to identify and characterize PTC foci. Using current histologic criteria for diagnosis, the specimens were divided into 3 groups: encapsulated variant (EV) (either with follicular or papillary architecture), usual variant (UV), and tall cell variant (TCV). Each group was further substratified according to the maximum tumor diameter: <1 cm, <2 cm, and ≥2 cm.
Results: Patient ages ranged from 23 to 76 years (54 ± 12) with a female-to-male ratio of 3:1. The predominant tumor was located in the right lobe, isthmus, and left lobe in 52%, 8%, and 40%, respectively, with sizes ranging from 3 to 60 mm (18.8 ± 6.6). The histologic variants TCV, EV, and UV accounted for 17, 24, and 59 cases, respectively. Three topographical patterns can be distinguished: (a) solitary nodule (n=24) with most cases being <1 cm; (b) predominant mass with adjacent satellite nodules (n=21) exhibiting varying degrees of fusion; and (c) similar to (b) but with discrete, isolated foci throughout the thyroid gland (n=55). For the latter group, most of the predominant tumor masses measured >2 cm. Topographical patterns (a), (b), and (c) were identified in 58.8, 33.3, and 10.2%; 5.9, 33.3, and 20.3%; and 35.3, 33.3, and 69.5% of the TCV, EV, and UV groups, respectively. For topographical pattern (c), bilateral involvement was seen in 72.7% of cases. Of the TCV, EV, and UV groups, 23.5, 20.8, and 52.5%, respectively exhibited bilateral involvement. The rate of bilaterality was statistically significant between tumors <1 cm and tumors <2 cm and ≥2 cm (p-values = 0.03 and 0.028, respectively).
Conclusions: TCV, EV, and small UV tend to be unifocal. Large UV are more often multifocal and bilateral. Secondary tumor nodules are most often located at the periphery of the main tumour and merged in a significant number of cases. Although intra-thyroidal lymphangitic spread cannot be excluded in this study, the topographical pattern of multifocality and the histopathology favor satellite tumor development in a zonal pattern around the main tumor mass with frequent superimposed field effect resulting in a random location throughout the thyroid gland.
Category: Head & Neck

Tuesday, March 5, 2013 9:30 AM

Poster Session III # 142, Tuesday Morning


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