A Case of Malignant Solitary Fibrous Tumor of the Hepatic Falciform Ligament

Solitary fibrous tumors (SFTs) are rare mesenchymal tumors that most commonly arise in the thoracic region.Most SFTs are benign; however, some show malignant behavior, such as local recurrence and distant metastasis.Here, we report the case of a 61-year-old man in whom an abdominal mass and multiple pulmonary nodules were incidentally detected on computed tomography (CT).Abdominal magnetic resonance imaging (MRI) showed a well-circumscribed solid tumor arising from the anterior surface of the liver that displaced the round ligament posteriorly.A gastrointestinal stromal tumor (GIST) was initially suspected; however, at laparotomy the tumor was found to arise from the falciform ligament, and a diagnosis of SFT was confirmed histopathologically.Immunohistochemically, the tumor was diffusely positive for STAT6, bcl-2, CD99, and vimentin, partially positive for cytokeratin AE1/AE3, and negative for CD34.Postoperatively, there was no local recurrence, but follow-up CT showed progressive enlargement of the bilateral pulmonary nodules and lymph nodes, and biopsy of a mediastinal lymph node confirmed metastatic SFT.The patient was transferred to a specialized cancer center for systemic therapy 13 months after surgery.To our knowledge, only two cases of SFT of the hepatic falciform ligament have been reported, and neither showed metastasis; the present case is the first with documented distant metastasis.Loss of CD34 expression and aberrant cytokeratin positivity, which have been associated with dedifferentiation and aggressive behavior in SFT, may identify extrapleural SFTs that warrant long-term surveillance for metastasis, although this observation from a single case requires confirmation.