Two separate malignancies in a multinodular goiter: A case report

Multinodular goiters are common benign lesions removed primarily for cosmetic reasons. The incidence of malignancy in a multinodular goiter is 4 to 14%. The commonest malignancy encountered is a papillary carcinoma. Medullary carcinoma accounts for 1 to 5% of thyroid malignancy but is responsible for approximately 13% of all thyroid cancer-related mortality.
We present the case of a 43-year-old female with a multinodular goiter having a TIRADS 3 nodule in the left lobe with no cervical lymphadenopathy. Cytology of this nodule revealed a Bethesda category 3 lesion, warranting a repeat FNAC. The repeat smear revealed similar cytology and was also reported as Bethesda category 3. Ideally, in such instances where the lesion is indeterminate, molecular testing should be done to guide clinical decision making. However, molecular testing is not routinely available in resource-limited settings such as Sri Lanka. Therefore, in keeping with the current guidelines for management of multinodular goiter, a total thyroidectomy was done. Histology showed a spindle cell tumour in the left lobe and a micropapillary carcinoma in the right lobe.  The spindle cell tumour was strongly positive for calcitonin, thereby confirming a medullary carcinoma.
This case reinforces the current guideline for the management of multinodular goiter with total thyroidectomy, especially in resource-limited settings such as Sri Lanka, where molecular testing is not freely available.