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Atypia of Undetermined Significance (AUS) and Follicular Lesion of Undetermined Significance (FLUS): A Histologic Correlation Study at a Single Institution
Abstracts 103 Cytologic Characterization of Tumors of Uncertain Malignant Potential of the Thyroid Lauren Parsons, MD, Bryan Hunt, MD, Nagarjun Rao, MD, FRCPath. Medical College of Wisconsin, Milwaukee, Wisconsin Introduction: Tumors of uncertain malignant potential (T-UMP) of the thyroid are encapsulated follicular cell tumors showing focal nuclear features of papillary thyroid carcinoma (PTC) or lacking clear capsular invasion. Unlike PTC, these tumors have a low risk of recurrence or metastasis. Cytologic assessment is the mainstay of evaluation of thyroid nodules; however, little exists in the literature describing the cytologic findings of T-UMP. We therefore sought to better characterize the features of T-UMP in fine needle aspiration (FNA) specimens. Materials and Methods: A search of the surgical pathology database for T-UMP yielded five cases with FNA of the nodule in question preceding resection. Cytology specimens were assessed for the following: colloid, overall cellularity, microfollicular architecture, pleomorphism, nuclear grooves, nuclear overlapping, and intranuclear pseudoinclusions. For comparison, five FNA specimens of excision-proven PTC were assessed for the same features. Results: Cytologic findings of all cases are summarized in Table 1. All T-UMP cases showed minimal colloid with at least moderate cellularity and nuclear pleomorphism (5/5 cases); this was also seen in all five cases of PTC. Prominent microfollicular architecture was seen in 4/5 cases of UMP tumors, with nuclear overlap in 3/5 cases. None of the UMP cases showed intranuclear pseudoinclusions, and only one case had nuclear grooves. In contrast, all five cases of PTC had showed nuclear overlap, nuclear grooves, and intranuclear pseudoinclusions. Conclusions: FNAs of T-UMP and PTC share some features, including a paucity of colloid, increased cellularity, and occasionally nuclear overlap and nuclear grooves. However, in our series, no T-UMP had intranuclear pseudoinclusions and none showed more than one of three nuclear features of PTC. Recognition that isolated features of PTC may be seen in T-UMP may help prevent overdiagnosis of PTC in T-UMP cases, and can help prevent unnecessary total thyroidectomy in these patients. Table 1
104 Atypia of Undetermined Significance (AUS) and Follicular Lesion of Undetermined Significance (FLUS): A Histologic Correlation Study at a Single Institution Ariana Beck, MD1, Frances Cate, MD2, Alice Coogan, MD2. 1Vanderbilt University Medical Center, Nashville, Tennessee; 2Vanderbilt University, Nashville, Tennessee Introduction: Our objective is to report our rate of AUS/FLUS diagnosis on thyroid cytology as well as histologic correlation of these lesions.
S53 Materials and Methods: Our database was reviewed to identify all cases of thyroid cytology diagnosed as AUS/FLUS from February 2009 through June 2012. The electronic medical record was reviewed on each patient. IRB approval was obtained. Results: 322 patients were diagnosed with AUS/FLUS out of 2311 patients with 3200 nodules (AUS/FLUS rateZ10%). Of the 322 patients, 129 directly underwent thyroidectomy, 102 had a repeat FNA, and 91 opted for conservative follow-up. Of the 129 thyroidectomy patients, 66 had a benign diagnosis, 38 had an adenoma (36 follicular and 2 Hürthle cell), and 25 had a malignancy (13 papillary thyroid carcinoma (PTC), 5 follicular variant of papillary thyroid carcinoma (FVPTC), 4 follicular carcinoma, 1 Hürthle cell carcinoma, 1 medullary carcinoma, and 1 metastatic renal cell carcinoma). Of patients who underwent repeat FNA, 44 had a benign diagnosis, 49 had a repeat diagnosis of AUS/FLUS, and 9 were suspicious for malignancy or malignant. 54 repeat FNA patients underwent thyroidectomy with diagnoses as follows: 26 benign, 16 follicular adenoma, 1 Hürthle cell adenoma, 8 FVPTC, and 3 PTC. Overall, 183 of the 322 patients with an AUS/FLUS diagnosis underwent thyroidectomy. Upon resection, the neoplastic rate (adenomas or malignancy) was 29% (54/183) and the malignancy rate was 19% (36/183). The overall malignancy rate of all AUS/FLUS nodules was 11% (36/322). Conclusions: A variety of diagnoses correlate with an FNA diagnosis of AUS/FLUS. The most common malignant diagnosis is PTC (5%), followed by FVPTC (4%). A dominant hyperplastic nodule in a background of multinodular goiter was the most common benign diagnosis associated with AUS/FLUS (13%).
105 Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance (AUS/FLUS): Experience and Surgical Follow-up From a Cancer Institution Chen Gao, MD, PhD, Mihai Merzianu, MD, Lourdes Ylagan, MD. Roswell Park Cancer Institute, Buffalo, New York Introduction: AUS/FLUS is a diagnostic category for thyroid samples with a degree of architectural abnormality and/or focal cytological atypia not meeting the criteria for suspicious or malignant diagnosis in the Bethesda system. Our institution began using this system of reporting thyroid fine needle aspiration (FNA) in October 2010. We report our experience with AUS/FLUS with follow-up excisional surgical correlation. Material and Methods: Pathology records for all thyroid FNA performed at our institution from January 1, 2011 through December 31, 2013 were reviewed. Cases with an AUS/FLUS diagnosis with subsequent surgical resection were retrieved and both cytology and surgical slides were re-examined. The study was approved by our IRB (BDR 043514) Results: AUS/FLUS diagnosis was issued in 79 of 603 (13%) thyroid FNAs during the period above. Surgical resection was performed in 42 (53.2%) cases with a malignant rate of 33.3% (Table 1). Microfollicles, minimal or absent colloid and focal nuclear atypia were the most frequent criteria used for an AUS/FLUS diagnosis (Table 2). Follicular variant of papillary thyroid carcinoma (FVPTC) was the most common malignant diagnosis. When cytologic features were compared between papillary thyroid carcinoma (PTC) (nZ3) and FVPTC (nZ7), the most common distinguishing feature on FNA for a diagnosis of FVPTC was presence of microfollicles, whereas for PTC they were: absence of colloid, presence of focal mildly nuclear atypia including enlarged nuclei, nuclear grooves, and presence of nucleoli (Table 3).
104 Atypia of Undetermined Significance (AUS) and Follicular Lesion of Undetermined Significance (FLUS): A Histologic Correlation Study at a Single Institution Ariana Beck, MD1, Frances Cate, MD2, Alice Coogan, MD2. 1Vanderbilt University Medical Center, Nashville, Tennessee; 2Vanderbilt University, Nashville, Tennessee Introduction: Our objective is to report our rate of AUS/FLUS diagnosis on thyroid cytology as well as histologic correlation of these lesions.
S53 Materials and Methods: Our database was reviewed to identify all cases of thyroid cytology diagnosed as AUS/FLUS from February 2009 through June 2012. The electronic medical record was reviewed on each patient. IRB approval was obtained. Results: 322 patients were diagnosed with AUS/FLUS out of 2311 patients with 3200 nodules (AUS/FLUS rateZ10%). Of the 322 patients, 129 directly underwent thyroidectomy, 102 had a repeat FNA, and 91 opted for conservative follow-up. Of the 129 thyroidectomy patients, 66 had a benign diagnosis, 38 had an adenoma (36 follicular and 2 Hürthle cell), and 25 had a malignancy (13 papillary thyroid carcinoma (PTC), 5 follicular variant of papillary thyroid carcinoma (FVPTC), 4 follicular carcinoma, 1 Hürthle cell carcinoma, 1 medullary carcinoma, and 1 metastatic renal cell carcinoma). Of patients who underwent repeat FNA, 44 had a benign diagnosis, 49 had a repeat diagnosis of AUS/FLUS, and 9 were suspicious for malignancy or malignant. 54 repeat FNA patients underwent thyroidectomy with diagnoses as follows: 26 benign, 16 follicular adenoma, 1 Hürthle cell adenoma, 8 FVPTC, and 3 PTC. Overall, 183 of the 322 patients with an AUS/FLUS diagnosis underwent thyroidectomy. Upon resection, the neoplastic rate (adenomas or malignancy) was 29% (54/183) and the malignancy rate was 19% (36/183). The overall malignancy rate of all AUS/FLUS nodules was 11% (36/322). Conclusions: A variety of diagnoses correlate with an FNA diagnosis of AUS/FLUS. The most common malignant diagnosis is PTC (5%), followed by FVPTC (4%). A dominant hyperplastic nodule in a background of multinodular goiter was the most common benign diagnosis associated with AUS/FLUS (13%).
105 Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance (AUS/FLUS): Experience and Surgical Follow-up From a Cancer Institution Chen Gao, MD, PhD, Mihai Merzianu, MD, Lourdes Ylagan, MD. Roswell Park Cancer Institute, Buffalo, New York Introduction: AUS/FLUS is a diagnostic category for thyroid samples with a degree of architectural abnormality and/or focal cytological atypia not meeting the criteria for suspicious or malignant diagnosis in the Bethesda system. Our institution began using this system of reporting thyroid fine needle aspiration (FNA) in October 2010. We report our experience with AUS/FLUS with follow-up excisional surgical correlation. Material and Methods: Pathology records for all thyroid FNA performed at our institution from January 1, 2011 through December 31, 2013 were reviewed. Cases with an AUS/FLUS diagnosis with subsequent surgical resection were retrieved and both cytology and surgical slides were re-examined. The study was approved by our IRB (BDR 043514) Results: AUS/FLUS diagnosis was issued in 79 of 603 (13%) thyroid FNAs during the period above. Surgical resection was performed in 42 (53.2%) cases with a malignant rate of 33.3% (Table 1). Microfollicles, minimal or absent colloid and focal nuclear atypia were the most frequent criteria used for an AUS/FLUS diagnosis (Table 2). Follicular variant of papillary thyroid carcinoma (FVPTC) was the most common malignant diagnosis. When cytologic features were compared between papillary thyroid carcinoma (PTC) (nZ3) and FVPTC (nZ7), the most common distinguishing feature on FNA for a diagnosis of FVPTC was presence of microfollicles, whereas for PTC they were: absence of colloid, presence of focal mildly nuclear atypia including enlarged nuclei, nuclear grooves, and presence of nucleoli (Table 3).