Medullary Thyroid Carcinoma in the background of non-neoplastic Toxic Nodular Goiter

Highlights of "Rare presentation of Medullary Thyroid Carcinoma in the background of non-neoplastic Toxic Nodular Goiter"•We call for clinicians to keep a high index of suspicion for malignancy in a thyroid nodule, irrespective of functional status of the nodule•Careful follow-up with periodic surveillance of the nodule is important, particularly in a patient with a history of another malignancy•measurement of calcitonin levels in the work-up of a thyroid nodule could serve as a useful diagnostic modality for a subset of patientsClinical Relevance:Meticulous follow-up should be emphasized in a subject discovered to have a thyroid nodule, particularly in a subject who has another malignancy. This is irrespective of initial investigations being negative for malignancy in the nodule. Genomic studies have shown a link between some breast and thyroid cancer types. Patients could benefit from early definitive therapy.Abstract:Background/ObjectiveMedullary thyroid carcinoma (MTC) is an uncommon thyroid cancer (TC), rarely found in hyperfunctioning goiter.Case ReportWe present a case of a woman treated for breast carcinoma (BCA), found to have a benign hyperfunctioning nodular goiter, its likely transformation to MTC and its treatment. Family history revealed papillary thyroid cancer (PTC) in her nephew.DiscussionMost TC in hyperfunctioning nodules are differentiated carcinomas. Familial MTC or MTC in association with Multiple Endocrine Neoplasia 2 is the expected genetic association in this case.ConclusionThe association of BCA and MTC may have been co-incidental, given the high prevalence of BCA in females. It could have been the result of a common genetic precursor of both tumours and/or treatment modality such as external beam radiation (EBRT) used to treat BCA. This case highlights the importance of considering MTC as a potential diagnosis even in cases of hyperfunctioning nodular goiter. We call for consideration of calcitonin level measurement in the work-up of thyroid nodules in select cases. Close follow-up of thyroid nodules, particularly in patients with another primary malignancy, is important due to possible common genotype triggers.