Diagnosing regenerative nodular hyperplasia, the "great masquerader" of liver tumors.

Distinguishing benign tumors and pseudotumors of the liver from malignant tumors is a common clinical problem. Regenerative nodular hyperplasia (RNH) represents one of the more challenging pseudotumors to diagnose, because they can appear clinically indistinguishable from either a primary or a secondary liver malignancy. Even after comprehensive radiologic evaluation and image-guided percutaneous biopsy, the diagnosis of RNH can remain elusive. We reviewed the pathophysiology of RNH and present five cases illustrating the limitations of percutaneous biopsy and the utility of laparoscopic wedge biopsy in establishing the diagnosis. All patients underwent a complete workup that included percutaneous biopsy. Patients with a nondiagnostic percutaneous biopsy underwent a laparoscopic wedge biopsy or anatomical resection. H&E, vimentin, trichrome, and reticulin staining as well as CD34 immunostaining were performed. Five patients were diagnosed with RNH between May 2002 and April 2004. Three had focal nodular disease, whereas the other two had a diffuse multinodular presentation. Percutaneous biopsy definitively made the diagnosis in only one out of the five cases. Laparoscopic wedge biopsy was necessary to accurately make the diagnosis in three cases, whereas the fifth diagnosis was established after an anatomical resection. RNH is a unique pseudotumor of the liver that can present either as a solitary nodule or as a multinodular process. Percutaneous biopsy is associated with limitations in diagnosing RNH, and a more definitive surgical biopsy may be required. When RNH is considered, laparoscopic wedge biopsy is a safe and efficient way to obtain enough tissue to preserve the hepatic architecture required for diagnosis, while avoiding the morbidity of an unnecessary open resection.