Cytomorphologic features of thyroid nodules harboring thyroid adenoma‐associated fusion: A single institutional review of 11 cases

Abstract

Background Thyroid adenoma‐associated (THADA) fusions are being identified more frequently with increased preoperative molecular testing on indeterminate thyroid fine‐needle aspirates (FNA). However, data on cytomorphologic features of THADA‐fusion thyroid lesions are limited. We examined cytomorphologic features of a THADA‐fusion thyroid FNA cohort with clinical, radiologic, and histologic data. Methods Our THADA fusion FNA cohort included 11 specimens from 11 patients with a mean age and F:M ratio of 56.5 years and 2.7:1, respectively. Ten cases had FNA slides available for review and five cases had histopathology. Air‐dried Diff‐Quik and alcohol‐fixed Papanicolaou smears, and formalin‐fixed cell blocks were reviewed and findings were correlated with the matched resection, when available. Clinical and radiologic data were obtained from the medical record. Results THADA fusion thyroid lesions were hypoechoic or isoechoic (80%), solid (80%) with well‐demarcated margins (100%) on ultrasound. Notable cytomorphologic features include crowded or prominent microfollicular groups (100%), scant colloid (91%), and mild nuclear atypia with nuclear grooves (100%), insignificant nuclear pleomorphism (100%), and without intranuclear pseudoinclusions (100%). All cases were classified as either atypia of undetermined significance (91%) or suspicious for follicular neoplasm (9%). Five resected cases were all low‐risk lesions (benign and malignant) with no evidence of recurrence in the limited available follow‐up. Conclusion THADA‐fusion thyroid FNAs show a crowded or prominent microfollicular pattern with mild nuclear atypia and without intranuclear pseudoinclusions, which overlaps with the cytomorphology of other RAS‐like thyroid lesions. In our cohort, resected THADA lesions were low risk on histologic analysis.

Comprehensive evaluation of cytomorphologic, histologic, and molecular features of DICER1‐altered thyroid lesions on FNA: A multipractice experience

“…Accordingly, it is feasible that the cytologic features described in our cohort are not representative of the entire cytomorphologic spectrum of DICER1‐altered thyroid lesions. We also recognize that the relatively bland cytomorphologic features seen with DICER1‐altered thyroid FNAs overlap with features reported for FNAs from other RAS‐like thyroid lesions 15,16 . Thus, it would be difficult to conclude preoperatively the presence of a DICER1 alteration primarily on cytomorphology.…”

“…We also recognize that the relatively bland cytomorphologic features seen with DICER1-altered thyroid FNAs overlap with features reported for FNAs from other RAS-like thyroid lesions. 15,16 Thus, it would be difficult to conclude preoperatively the presence of a DICER1 alteration primarily on cytomorphology. seen in all but one of our resected cases.…”

Pitfalls in Thyroid Fine-Needle Aspiration Cytopathology: An Approach to Atypical Findings

“…Therefore, many experts advise stringent adherence to the major diagnostic features of PTC to avoid false-positive diagnosis [20]. Interestingly, some authors have also found important genotype-phenotype correlates, with an overrepresentation of THADA gene fusions in benign thyroid lesions with occasional nuclear grooves [21]. It is also equally important to note that other malignant tumors of the thyroid gland can display few but not all cytological features of PTC, such as intranuclear grooves or occasional nuclear inclusions, features that may be encountered in medullary thyroid carcinoma (MTC) and oncocytic thyroid carcinoma [22,23].…”

THADA‐IGF2BP3 fusions detected in fine‐needle aspiration specimens of thyroid nodules: An institutional experience

“…[11][12][13] Interestingly, despite the association between IGF2BP3 and cancer and though some thyroid neoplasms with THADA-IGF2BP3 fusions can be large sized, overall thyroid lesions with such fusions appear to be low-risk neoplasms such as non-invasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP). [14][15][16] However, only a few case series are available within the literature [15][16][17][18][19][20] and at least one study supports evidence that IGF2BP3 is an adverse prognostic factor for a subset of poorly-differentiated thyroid carcinomas. 21 Here, we sought to investigate all instances of thyroid nodules with THADA-IGF2BP3 fusions at our institution to define the significance of this molecular alteration more clearly in FNA specimens.…”