Thyroid Mucosa-associated Lymphoid Tissue Lymphoma Presenting as Intermediate-risk Thyroid Nodule with Positive KRAS Mutation

Background/Objective: Little is known about the epidemiology, clinical presentation, and diagnosis of thyroid mucosa-associated lymphoid tissue (MALT) lymphoma. Case ReportWe report the case of a 67-year-old woman who presented with an intermediate-risk thyroid nodule 8 years after diagnosis of hypothyroidism due to Hashimoto's. She was found to have a well-circumscribed hypoechoic 2.6-cm right-sided thyroid nodule lobe, which was biopsied and returned atypia of undetermined significance with positive KRAS mutation on the Thyroseq V3 Genomic Classifier. She subsequently underwent right thyroid lobectomy and was found to have thyroid MALT lymphoma on histopathological sections. After the surgery, she was referred to oncology for further management of the thyroid MALT lymphoma. A positron emission tomography/computed tomography scan was performed for complete staging and revealed diffuse fluorodeoxyglucose uptake in the residual left thyroid lobe without evidence of extrathyroidal involvement. Her case was discussed in a multidisciplinary fashion among oncology, endocrine surgery, and endocrinology. Given the positron emission tomography scan findings, she ultimately underwent completion thyroidectomy 4 months after the initial surgery to rule out residual disease. The patient tolerated the operation well without complication. DiscussionOur report adds to the literature that Hashimoto's thyroiditis may be a risk factor of thyroid MALT lymphoma. Localized thyroid MALT lymphoma may be managed with total thyroidectomy. ConclusionWe report a patient with localized thyroid MALT lymphoma who presented with an intermediate-risk nodule with positive KRAS mutation and was treated with total thyroidectomy.