[599] Incidence of Thyrioid Malignancy in Completion Thyroidectomy – A Single Institution Experience over Ten Years

Zhihong Hu, Zulfiya Ibragimova, Umesh Kapur, Razan M Wafai, Swati Mehrotra. Loyola University Medical Center, Maywood, IL

Background: To do or not to do completion thyroidectomy (CT) for well differentiated thyroid cancers has been subject of debate for several years. While the procedure perse has minimal complications in experienced hands; surgery implies lifelong thyroid hormone supplementation for the patient. In addition many of the CT specimens have benign histology.
Design: A retrospective analysis of histologic findings in CT specimens was performed in patients undergoing the above procedure for a prior malignant diagnosis in lobectomy. The incidence and type of cancer in CT spceimens were assessed and conclusions drawn for rationale of the procedure.
Results: Between 1990 and 2011, 127 patients (female: 102; male: 25, age 48.6 ± 16.1 years) underwent CT. 73 of 127 patients with a diagnosis of either papillary thyroid cancer (PTC) or follicular carcinoma (FC) on lobectomy were included for review. 60 patients had PTC and 13 FC (n=11 minimally invasive and n=2 angioinvasive). 32 of 73 patients had a malignant diagnosis in CT. CT for all minimally invasive FC (n=11) showed benign histology. Of the two angioinvasive FC, one showed residual FC while the other had a microPTC in the CT specimen. The incidence was significantly higher (50%) when CT was performed for a prior diagnosis of PTC; however did not show any association with tumor size or number of tumor foci (p>0.05). CT performed for a follicular variant of PTC had a statistically significant (P<0.05) incidence of benign histology.

The consistency of malignant diagnosis in initial lobectomy with completion thyroidectomy

	Initial lobectomy	Completion thyroidectomy	%Consistency
Minimally invasive follicular carcinoma	11	0	0%
Angioinvasive follicular carcinoma	2	2	100%
Papillary carcinoma	60	30 (19 microPTC)	50%

The correlation of histologic characteristics of papillary carcinoma (initial diagnosis) to the incidence of malignancy in completion thyroidectomy

Initial diagnosis Classification	Sub- classification	Number of patients (n)	CT diagnosis Benign	CT diagnosis Malignant	p value
Size	<1.0cm (pT1a)	46	26	20
	1-2cm (pT1b)	11	8	3	>0.05
	>2cm (pT2)	3	1	2
Focus/foci	1	37	27	10
	>=2	23	8	15	>0.05
Variants	Conventional	34	15	19
	Follicular	26	20	6	0.04∗

Conclusions: CT with subsequent lifelong thyroid supplementation can be deferred in patients with minimally invasive FC and follicular variant of PTC. We also conclude that due to a high incidence of malignancy in CT for microPTC and no universally accepted protocol for their management, CT is a feasible option in these patients.
Category: Endocrine

Monday, March 19, 2012 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 95, Monday Morning