Background
Medullary thyroid carcinoma (MTC) is a rare neuroendocrine primary thyroid tumor, originating from the parafollicular C-cells of the thyroid gland. These aggressive cancers constitute approximately 3-10% of all primary thyroid malignancies, and are mainly sporadic (75%) [1,2]. Sporadic cases of MTC are usually diagnosed within the fourth to sixth decades of life and commonly manifest as a solitary thyroid nodule [3]. In about 5-10% of patients with MTC who have a palpable thyroid nodule, distant metastatic disease is present at presentation [1,4,5]. These tumors tend to metastasize to the kidneys, liver, lungs, bones, and less frequently, to the brain and skin [6,7]. Lung metastases occur in 33% of patients with locally advanced or metastatic MTC [8] and usually have a macronodular appearance; however, calcified pulmonary metastases, reticulonodular perihilar lesions and micronodular lesions have also been reported in several studies [9,10]. According to the literature, micronodular densities are more often associated with papillary thyroid carcinoma [10]. Here, we report the case of a middle-aged woman with metastatic medullary carcinoma of the thyroid presenting with an unusual miliary pattern on chest imaging mimicking that of miliary tuberculosis.