Mesenchymal hamartoma of the liver.

Mesenchymal hamartomas of the liver are the second most common benign liver tumor of childhood. The experience with this tumor at Egleston's Children Hospital at Emory University from 1989 to 1994 is reviewed. Eight patients presented with abdominal distention or an upper abdominal mass. Six patients presented at a mean age of 8 months, and two patients presented at 17 and 23 years of age, respectively. Four patients displayed normal alpha-fetoprotein levels, whereas one patient had an elevated level. Liver function studies were normal in all patients. Abdominal ultrasonography and CT scans revealed a cystic, septated mass within the liver or on a pedicle in all patients. Five patients had simple excision of the tumor, and two had major hepatic resections. The cysts were multiloculated and lined with cuboidal bile duct epithelium surrounded by stroma containing proliferating bile ducts, blood vessels, and compressed liver tissue with no calcifications. In one patient, some pathologists favored the diagnosis of malignant myxoid fibrous histiocytoma because of similar-appearing stroma. Follow-up (mean, 35 months) revealed one symptomatic recurrence after initial resection was incomplete. There were no other recurrences and no malignant transformations. A septated, noncalcified, cystic hepatic mass in an infant with normal liver function studies and characteristic ultrasound or CT is likely a benign mesenchymal hamartoma that can be cured by total local excision.