Hepatic Lesions in a Cirrhotic Liver: Primary or Metastases?

DISCUSSION

Medullary thyroid carcinoma is a neuroendocrine tumor of the parafollicular cells (C cells), which secrete calcitonin and also carcinoembryonic antigen. Somatostatin receptor scintigraphy is an important tool in staging of neuroendocrine tumors; however, regarding liver lesions seen in this case, the study could not differentiate between neuroendocrine tumors and HCC given that previously published studies showed that in advanced HCC cases, ¹¹¹In-pentetreotide study can also be positive.

Several studies indicate that cirrhotic liver reduces the risk of hepatic metastases (1). LI-RADS categories reflect estimated probability for a lesion to be HCC (2). Hypervascularity in the late arterial phase and rapid washout in the portal-venous phase and especially in the delayed phase satisfy the LI-RADS 5 criteria for diagnosis of HCC and give a good sensitivity for HCC detection. However, recent studies showed that an interpreter is more likely to perceive washout in a nodule with a capsule than a nodule without a capsule, despite the absence of objective evidence of washout or significant arterial enhancement (3).

Metastases from neuroendocrine tumor are hypervascular and commonly show washout and can be assigned as LI-RAD 5, resulting in a false-positive diagnosis of HCC. Therefore, attention to any atypical features is important in correct classification of these lesions. In the current case, there was only mild arterial enhancement. Also, the presence of calcification, which is relatively infrequent in nonfibrolamellar HCC, might have been a clue that this was not a typical case of HCC and that the lesions must have been categorized as LI-RADS M. There were coarse calcifications with a similar morphology in a thyroid nodule and in several mediastinal lymph nodes, which were also initially overlooked. Coarse calcifications are less specific for malignancy compared with microcalcifications and can be seen in multinodular goiter secondary to dystrophic calcifications in benign thyroid nodules; however, when present in a solitary thyroid nodule they carry a higher risk of being malignant. Dense and irregular coarse thyroid calcifications may coexist with microcalcifications in papillary thyroid cancer (which only in exceedingly rare cases metastasize to the liver), and they are the most common type of calcifications in medullary thyroid carcinomas (4). Incidence of calcified metastasis in the mediastinal lymph nodes, liver, and lung at the initial presentation has been described in patients with medullary thyroid carcinomas, and this feature needs not to be confused with granulomatous disease when searching for a neuroendocrine primary site (5).