[Rare mesenchymal lesions in siblings. Two case reports].

We report on a 15-month-old boy presenting a juvenile active ossifying fibroma in the right nasal cavity and the sibling, a 9-month-old girl with a mesenchymal hamartoma of the chest wall. The two lesions showed many similarities. Both lesions are present at the time of birth or in early life with local obstructive or compressive effects. The lesions have a similar mixture of mature and immature mesenchymal tissue with areas of ossification. The entities present a tumor-like development with an abnormal mixture of tissue indigenous to the specific area of the body without notable atypical cytologic features. These features are typical criteria for hamartoma lesions.