A 6-month-old boy presented with a large abdominal mass that proved to be a cystic hepatic mesenchymal hamartoma occupying both hepatic lobes. During fetal life, a bulky, abnormal, cystic placenta had been present, which on histological examination was diagnosed as mesenchymal stem villous hyperplasia. This association has not previously been reported.

Summary Five cases of atypical hydatid cyst of the kidney are present. Four cases simulated kidney tumours and 1 an infectious lesion, but were misdiagnosed on account of the absence of the typical signs and finding of hydatid disease. With the increase in world travel hydatid disease should be included in the differential diagnosis of all other kidney masses, especially when they are atypical.