Prevalence of Contralateral Tumors in Patients with Follicular Variant of Papillary Thyroid Cancer.

BACKGROUND: Thyroid lobectomy alone is being performed increasingly for patients with encapsulated follicular variant of papillary thyroid carcinoma (fvPTC). However, the prevalence of contralateral disease in these patients is unknown. We investigated the presence of synchronous disease in fvPTC to improve decision making about the extent of surgical resection and need for surveillance.

STUDY DESIGN: We performed a retrospective review of patients who underwent thyroid surgery from October 2009 to February 2013 with a diagnosis of fvPTC as their primary lesion. We collected information on patient demographics, nodule size, multifocality, fine-needle aspiration results, lymphovascular invasion, extrathyroidal extension, and lymph node metastasis. Tumors were divided into noninvasive and invasive/infiltrative fvPTC categories. Characteristics of solitary and bilateral fvPTC were compared.

RESULTS: We identified 124 patients with final pathology demonstrating fvPTC. The most common fine-needle aspiration diagnosis was "suspicious for malignancy" (n = 53). Sixty-five contralateral tumors were identified in 44 of 124 patients (35.5%) and included fvPTC (n = 40), classical PTC (n = 22), tall cell PTC (n = 2), and follicular carcinoma (n = 1). Fifty contralateral tumors were 1 to 5 mm, 10 measured 6 to 9 mm, and 5 were ≥10 mm. Contralateral disease correlated significantly with lymphovascular invasion (p = 0.037) and larger primary lesions (p = 0.020). There was no significant difference noted in extrathyroidal extension or lymph node metastasis. Both noninvasive and invasive/infiltrative fvPTC demonstrated similar rates of contralateral disease.

CONCLUSIONS: Bilateral disease is common in fvPTC, primarily in the form of papillary microcarcinomas. Future monitoring of the contralateral lobe should be discussed with fvPTC patients who do not undergo completion thyroidectomy.