Segmental atrophy of the liver: a distinctive pseudotumor of the liver with variable histologic appearances.

Segmental atrophy of the liver can lead to the formation of a pseudotumor that can pose a diagnostic challenge. To better understand the full clinicopathologic spectrum of this pseudotumor, 18 cases were studied. Ages at presentation ranged from 14 to 91 years (median, 63 y) with a modest female-patient predominance (13 of 18, 72%). Upper right quadrant abdominal pain was the most common clinical presentation (14 of 18, 78%), and all the cases were mass lesions. The majority of cases were subcapsular (15 of 18, 83%) and ranged in size from 1.8 to 10.0 cm. All the cases contained abnormally thick-walled and often thrombosed vessels, with both arteries and veins affected. Biliary cysts were a common finding (7 of 18, 39%). Examination of the entire series of cases suggested a sequence of changes, with early lesions (n = 4) composed of collapsed hepatic parenchyma with preservation of portal areas, occasional islands of residual hepatocytes, and brisk bile ductular proliferation. These cases showed very mild elastosis. Other cases (n = 10) showed little or no ductular proliferation but had increased levels of elastosis. More advanced lesions (n = 3) were composed almost solely of elastosis with small scattered islands of unremarkable hepatocytes, whereas an end-stage lesion (n = 1) was a discrete nodule of fibrosis. In conclusion, segmental atrophy of the liver is typically subcapsular, and is strongly associated with vascular injury. The lesion has multiple stages ranging from parenchymal collapse, to nodular elastosis, to nodular fibrosis. Recognizing the various morphologies will aid in proper diagnosis.