Endocrine Abstracts (2011) 26 P475

Prevalence and features of incidental thyroid carcinoma in 1955 patients surgically treated for benign lesions

M Perrino1, C Colombo1, L Vicentini3, G Cantoni3, L Poggi3, P Beck-Peccoz1,2 & L Fugazzola2

1Department of Medical Science, University of Milan, Milan, Italy; 2Endocrine Unit, Fondazione IRCCS Ca’ Granda, Milan, Italy; 3Endocrine Surgery Unit, Fondazione IRCCS Ca’ Granda, Milan, Italy.

Incidental thyroid carcinoma (IC) is defined as a tumor diagnosed at histology after surgery for benign diseases and without a preoperative diagnosis of malignancy. Since the prevalence of IC reported in the literature is extremely variable (4.6–17%), mostly due to the limited number of cases, we aimed to study the features of IC in our large series. We retrospectively evaluated 1955 patients who consecutively underwent total thyroidectomy for non malignant diseases from 1998 to 2010 in our Endocrine Surgery Centre. The pre-surgical diagnoses were of uni-multinodular goiter, toxic adenoma or Graves’ disease. Moreover, 211 patients had a preoperative cytological diagnosis of micro-follicular lesion. Overall, an IC was found in 251 (12.8%) patients, and the diagnosis was of papillary or follicular carcinoma in 90 and 9% of cases, respectively. Poorly differentiated carcinoma or lymphoma were found in two patients. The prevalence was higher in patients with a preoperative diagnosis of micro-follicular lesion (64/211, 30%) and toxic adenoma (4/17, 23%), compared to patients with Graves’s disease (25/258, 9.7%), with uni-or multinodular non-toxic goiter (142/123, 11.5%) or with toxic multinodular goiter (16/231, 7%). The TNM staging was pT1NX-N0 in 75% of cases (81% were microcarcinomas ≤1 cm) and pT2NX-N0 in 6.8% of patients. An extra-thyroidal invasion (pT3-T4NX-N0) was found in 10.7% of tumors, and lymph node metastases (pT1-T4N1) were diagnosed in 6.3% of patients. In conclusion, in a large series of patients submitted to thyroidectomy for benign diseases, a high prevalence (12.8%) of IC was found. Although most of the tumors were small and intra-thyroidal, a significant proportion of carcinomas showed extra-thyroidal invasion or lymph node involvement. Thus, present data indicate the need to perform an accurate preoperative evaluation in patients with benign diseases regardless of the association with thyroid autoimmunity or hyperfunction.

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