Answer: Nasal chondromesenchymal hamartoma

Histology: The specimen consists of a polypoid fragment of respiratory mucosa. The submucosal glands are cytically distended by inspissated mucous. The stalk is fibrotic and edematous. There are scattered lymphocyes but relatively few eosinophils. At the tips of the polyp, the stroma condenses into cellular nodules that take on a very chondroid appearance. These chondroid nodules are S100 positive.

Discussion: Nasal chondromesenchymal hamartoma is a benign mass lesion of the nasal cavity predominantly described in young infants. They are often present at birth and thus have generally been regarded as developmental or congenital in origin, but they can sometimes arise in older children and adults. Patients may present with nasal obstruction, epistaxis, or persistent rhinorrhea. These unusual lesions are composed of a proliferation of mesenchymal and cartilaginous elements. The cartilaginous and mesenchymal stromal component in all cases stained consistently with S100, with stronger staining in the cartilaginous components. Their pathogenesis is unknown, but they follow a benign course and do not recur after excision.

The most common sinonasal polyp, the inflammatory poly (i.e. allergic polyp), do not typically arise in young children. Accordingly, when a sinonasal polyp is encountered in a child, one should always consider the possibility of a sinonasal polyp of cystic fibrosis. In the present case, clinical testing for cystic fibrosis was negative. The presence of cartilaginous nodules in a midline location of a child should also raise the possibility of a teratoma, but derivative of other germ cell layers were not present in this lesion.