Unusual choristoma of the parotid gland in a girl. A possible trichoadenoma.

An 8-year-old girl had a painless circumscribed nodule in the right parotid gland for 4 weeks. A tumour (1.3 cm diameter) within the salivary gland parenchyma showed small cystic spaces with horn-like material macroscopically. The tumour tissue contained solid squamous cell formations and cystic spaces limited by multilayered squamous epithelium and covered by layers of ortho- and parakeratotic cells. The cystic spaces contained keratotic lamellae. In some areas pin-like epithelial proliferations were seen. All epithelial cells were characterized by uniform nuclei, and no atypical mitoses were seen. Keratinizated masses with partial calcification were occasionally located in the interstitial tissue and replaced by multinucleated giant cells. The tumour was classified as a choristoma and resembled a trichoadenoma. The ectodermally derived oral and salivary gland epithelium may be the source of skin-like or adnexal tumours.