Toxic Adenoma Mimicking Papillary Thyroid Carcinoma

Abstract

Introduction/Objective A thyroid nodule requires multiple steps in the identification of its nature, which determines its management. In most cases, low TSH levels support a benign origin. However, examples of hyperfunctioning thyroid carcinoma have been reported. Recent observations show that the number of thyroid cancer increases with the prevalence in young patients. The ambiguity of some cases necessitates the use of a full range of diagnostic methods up to molecular cytological diagnostics. Methods We present a report on the case of an 11-year-old boy complaining of weight loss despite having a good appetite. Results The blood test showed free T4 1.51 (0.81 - 1.35 ng/dL), free T3 6.04 (3.31 - 4.88 pg/mL), and TSH 0.01 (0.662 - 3.90 mU/L). During sonography, the left thyroid lobe was almost completely replaced by an isoechogenic circumscribed mass with multiple colloid cystic spaces. No suspicious microcalcifications or abnormal cervical lymph nodes were identified. A thyroid scan revealed the presence of a toxic autonomously functioning thyroid nodule in the left lobe. Methimazole and propranolol were prescribed, with subsequent left hemithyroidectomy on 10/21/2019. Grossly, the left thyroid lobe was 3.4 x 2.5 x 2 cm. The sectioning revealed light brown homogeneous stroma with a well-defined yellow-tan nodule (1.1 x 1.1 x 1 cm) in the middle of the lobe. The specimen was entirely submitted for permanent fixation in formalin. Microscopically, an encapsulated nodule was seen with the follicular and focal papillary pattern; nuclear features strongly and multifocally suggested a diagnosis of papillary carcinoma. HBME1 and calcitonin immunostains were negative; CK19 immunostain was multifocally positive. Next-generation sequencing supported the diagnosis of toxic adenoma with atypical features. Conclusion Every case of thyroid neoplasm should be fully investigated using modern and high-tech technologies, regardless of the functioning state of the gland. Molecular testing is supportive, especially in ambiguous situations, which benefits the patient.