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Diagnosis and reporting of follicular-patterned thyroid lesions by fine needle aspiration.

Faquin WC - Head Neck Pathol (2009)

Bottom Line: Based primarily upon the cytoarchitectural pattern, FNA is used as a screening test for follicular-patterned lesions to identify the majority of patients with benign nodules who can be managed without surgical intervention.A key element of this approach is the category "atypical cells of undetermined significance" (ACUS) which is used for those aspirates which cannot be easily classified as benign, suspicious, or malignant.The recommended follow-up for an ACUS diagnosis is clinical correlation and in most cases, repeat FNA sampling.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114, USA. WFaquin@Partners.org

ABSTRACT
Over the past 3 decades, fine needle aspiration (FNA) has developed as the most accurate and cost-effective initial method for guiding the clinical management of patients with thyroid nodules. Thyroid FNA specimens containing follicular-patterned lesions are the most commonly encountered and include various forms of benign thyroid nodules, follicular carcinomas, and the follicular variant of papillary thyroid carcinoma. Based primarily upon the cytoarchitectural pattern, FNA is used as a screening test for follicular-patterned lesions to identify the majority of patients with benign nodules who can be managed without surgical intervention. The terminology and reporting of thyroid FNA results have been problematic due to significant variation between laboratories, but the recent multidisciplinary NCI Thyroid FNA State of the Science Conference has provided a seven-tiered diagnostic solution. A key element of this approach is the category "atypical cells of undetermined significance" (ACUS) which is used for those aspirates which cannot be easily classified as benign, suspicious, or malignant. Lesions in this category represent approximately 3-6% of thyroid FNAs and have a risk of malignancy intermediate between the "benign" category and the "suspicious for a follicular neoplasm" category. The recommended follow-up for an ACUS diagnosis is clinical correlation and in most cases, repeat FNA sampling.

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This thyroid FNA contains occasional follicular cells with enlarged, pale, grooved nuclei in an otherwise benign aspirate, and is therefore diagnosed as “Atypical cells of undetermined significance (ACUS).” (Papanicoloau stain)
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Fig5: This thyroid FNA contains occasional follicular cells with enlarged, pale, grooved nuclei in an otherwise benign aspirate, and is therefore diagnosed as “Atypical cells of undetermined significance (ACUS).” (Papanicoloau stain)

Mentions: While most follicular-patterned lesions can be accurately assessed using thyroid FNA, a small subset of lesions exhibit cytologic features that are intermediate between benign and neoplastic. This so-called “indeterminate” category has been used in various ways by different laboratories. Some have used this category for any aspirate with atypia, for others the category has been used to mean “indeterminate for malignancy” or “indeterminate for neoplasia.” In the proposed Bethesda System for thyroid cytology, the ACUS or indeterminate category is specifically designated for use when the ‘cytologic and/or architectural atypia encountered is of uncertain significance: it is of an insufficient degree to qualify for any of the suspicious or malignant categories’ [18]. At the same time, the cytologic or architectural atypia is more than would be acceptable within the “benign” category. There are many different situations in which an ACUS diagnosis would be used, but some of the most common include the following: (1) a sparsely cellular aspirate with a predominance of microfollicles, (2) cytologic atypia in the setting of preparation artifact, (3) a mixed cytoarchitectural pattern that includes nearly equal proportions of macrofollicles and microfollicles (Fig. 4), (4) focal atypia suggestive of papillary carcinoma in an otherwise predominantly benign-appearing sample (Fig. 5). Because of the potential to overuse the ACUS category, it should be less than 7% of all thyroid FNA interpretations [18]. For thyroid aspirates diagnosed as ACUS, the recommended management is clinicoradiologic correlation and in most cases, a repeat FNA. The latter will often result in a more definitive “benign,” “suspicious,” or “malignant” designation; however, 20–25% of cases will result in a second ACUS diagnosis [13, 18]. The risk of malignancy for an ACUS diagnosis is difficult to assess because only a subset of ACUS nodules will be surgically excised. However, it is estimated that the overall risk of malignancy will be approximately 5–10% which is intermediate between the “benign” and “suspicious for a follicular neoplasm” categories [18].Fig. 4


Diagnosis and reporting of follicular-patterned thyroid lesions by fine needle aspiration.

Faquin WC - Head Neck Pathol (2009)

This thyroid FNA contains occasional follicular cells with enlarged, pale, grooved nuclei in an otherwise benign aspirate, and is therefore diagnosed as “Atypical cells of undetermined significance (ACUS).” (Papanicoloau stain)
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2807535&req=5

Fig5: This thyroid FNA contains occasional follicular cells with enlarged, pale, grooved nuclei in an otherwise benign aspirate, and is therefore diagnosed as “Atypical cells of undetermined significance (ACUS).” (Papanicoloau stain)
Mentions: While most follicular-patterned lesions can be accurately assessed using thyroid FNA, a small subset of lesions exhibit cytologic features that are intermediate between benign and neoplastic. This so-called “indeterminate” category has been used in various ways by different laboratories. Some have used this category for any aspirate with atypia, for others the category has been used to mean “indeterminate for malignancy” or “indeterminate for neoplasia.” In the proposed Bethesda System for thyroid cytology, the ACUS or indeterminate category is specifically designated for use when the ‘cytologic and/or architectural atypia encountered is of uncertain significance: it is of an insufficient degree to qualify for any of the suspicious or malignant categories’ [18]. At the same time, the cytologic or architectural atypia is more than would be acceptable within the “benign” category. There are many different situations in which an ACUS diagnosis would be used, but some of the most common include the following: (1) a sparsely cellular aspirate with a predominance of microfollicles, (2) cytologic atypia in the setting of preparation artifact, (3) a mixed cytoarchitectural pattern that includes nearly equal proportions of macrofollicles and microfollicles (Fig. 4), (4) focal atypia suggestive of papillary carcinoma in an otherwise predominantly benign-appearing sample (Fig. 5). Because of the potential to overuse the ACUS category, it should be less than 7% of all thyroid FNA interpretations [18]. For thyroid aspirates diagnosed as ACUS, the recommended management is clinicoradiologic correlation and in most cases, a repeat FNA. The latter will often result in a more definitive “benign,” “suspicious,” or “malignant” designation; however, 20–25% of cases will result in a second ACUS diagnosis [13, 18]. The risk of malignancy for an ACUS diagnosis is difficult to assess because only a subset of ACUS nodules will be surgically excised. However, it is estimated that the overall risk of malignancy will be approximately 5–10% which is intermediate between the “benign” and “suspicious for a follicular neoplasm” categories [18].Fig. 4

Bottom Line: Based primarily upon the cytoarchitectural pattern, FNA is used as a screening test for follicular-patterned lesions to identify the majority of patients with benign nodules who can be managed without surgical intervention.A key element of this approach is the category "atypical cells of undetermined significance" (ACUS) which is used for those aspirates which cannot be easily classified as benign, suspicious, or malignant.The recommended follow-up for an ACUS diagnosis is clinical correlation and in most cases, repeat FNA sampling.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114, USA. WFaquin@Partners.org

ABSTRACT
Over the past 3 decades, fine needle aspiration (FNA) has developed as the most accurate and cost-effective initial method for guiding the clinical management of patients with thyroid nodules. Thyroid FNA specimens containing follicular-patterned lesions are the most commonly encountered and include various forms of benign thyroid nodules, follicular carcinomas, and the follicular variant of papillary thyroid carcinoma. Based primarily upon the cytoarchitectural pattern, FNA is used as a screening test for follicular-patterned lesions to identify the majority of patients with benign nodules who can be managed without surgical intervention. The terminology and reporting of thyroid FNA results have been problematic due to significant variation between laboratories, but the recent multidisciplinary NCI Thyroid FNA State of the Science Conference has provided a seven-tiered diagnostic solution. A key element of this approach is the category "atypical cells of undetermined significance" (ACUS) which is used for those aspirates which cannot be easily classified as benign, suspicious, or malignant. Lesions in this category represent approximately 3-6% of thyroid FNAs and have a risk of malignancy intermediate between the "benign" category and the "suspicious for a follicular neoplasm" category. The recommended follow-up for an ACUS diagnosis is clinical correlation and in most cases, repeat FNA sampling.

Show MeSH
Related in: MedlinePlus