Hepar lobatum is an acquired liver deformity mostly known as the end-stage of tertiary syphilis. The authors report two cases of hepar lobatum resulting from metastatic mammary ductal carcinoma in the liver and reassess the clinicopathologic features of seven previously reported cases (two in the German language). A liver of near-normal weight with an irregularly lobulated contour, capsular indentations/crevices from which intersecting (carcinoma-bearing) fibrous septa extended deep into the parenchyma, a predominant centrifugal distribution of lesional areas, and many septa abutting on the degenerated center of tumor nodules were the salient gross features. No significant tumor/fibrous occlusion of intrahepatic branches of portal or hepatic veins, nor cirrhotic type nodular hepatocellular regeneration was observed. Both of these patients experienced a drastic decrease in CEA serum levels during multiagent palliative chemotherapy. In one patient, abundant macrophages in conjunction with minimal residual tumor were present within intrahepatic septa. The pathogenesis of this condition appears largely related to an active phase of chemo-induced tumor regression with subsequent tissue collapse, followed by an organizing phase of healing and scar contraction.