Primary adamantinoma of the rib. Unusual presentation for a bone neoplasm of uncertain origin.

Adamantinomas are rare, low-grade malignant intra-osseous tumors composed of epithelial and mesenchymal elements, which show a marked predilection for the tibia and fibula of young adult male patients. Although cases of adamantinoma located to the axial skeleton have been reported either as recurrent or metastatic disease, only two cases of primary adamantinoma located to the thoracic wall have been previously described. In this study we present the clinical, radiological and histopathological features of a 24-year-old male with a slow growing, solid-cystic, painful mass, located to the right 11th rib, which was morphological and immunohistochemically diagnosed as a primary classic adamantinoma. Radiological studies showed a multiloculated lesion with a solid component. The patient underwent a whole surgical resection of the lesion. Histologically, multiple foci of epithelial cells with basaloid and squamous components were found intermixed within a fibrous stromal tissue. Immunohistochemical analysis demonstrated expression of cytokeratins, EMA, vimentin and other epithelial markers. Primary affection of the rib is an unusual feature of classic adamantinomas.