Rare Extrahepatic Metastasis of Hepatocellular Carcinoma to the Left Triangular Ligament: A Case Report

The left triangular ligament is an uncommon site of heterotopic liver tissue, from which ectopic hepatocellular carcinoma (HCC) may arise. In contrast, extrahepatic metastasis from an intrahepatic primary HCC to the triangular ligament appears to be extremely rare. To the best of our knowledge, within the scope of our structured search of the English-language literature (PubMed and Web of Science), we did not identify a pathologically confirmed report of an isolated metastasis to the left triangular ligament from an orthotopic HCC. We report a case of isolated HCC metastasis to the left triangular ligament discovered incidentally during laparoscopic hepatectomy, which posed a differential diagnostic challenge between ectopic HCC and extrahepatic metastasis.

A 62-year-old man was referred for evaluation of increasing serum alpha-fetoprotein (AFP) levels (27772 ng/mL). Dynamic contrast-enhanced CT revealed an approximately 25-mm hypervascular tumor in segment 2 with washout, consistent with HCC, and laparoscopic left lateral sectionectomy was planned. Intraoperatively, during mobilization of the left lateral section, an unexpected flat, white lesion was identified within the left triangular ligament, adjacent to but clearly separate from the primary tumor and liver parenchyma. Because malignancy could not be excluded, the triangular ligament was transected on the diaphragmatic side and resected en bloc with the planned specimen. Histopathological examination showed the segment 2 tumor to be well- to moderately differentiated HCC, whereas the triangular ligament lesion consisted of poorly differentiated HCC. The lesion was located entirely within the peritoneal fold, enclosed by peritoneal tissue, without intervening normal hepatic parenchyma or macroscopic/microscopic continuity with the primary tumor. These findings supported the diagnosis of isolated extrahepatic metastasis rather than ectopic HCC. The final pathological stage was pT2N0M1, pStage IVB (Union for International Cancer Control TNM, 8th edition). The postoperative course was uneventful, and the patient has remained recurrence-free with normalized AFP for 5 years.

This case demonstrates an unusual pattern of HCC spread to the left triangular ligament, a site also known for ectopic HCC. Accurate diagnosis required integration of intraoperative findings and histopathological features. Careful inspection of the triangular ligament during left-sided mobilization should be considered to detect occult lesions and facilitate complete resection.