Malignancy arising in adamantinomatous craniopharyngioma: Report of a rare case with unusual morphologic features.

Adamantinomatous craniopharyngioma is a grade 1 tumor that arises in a sellar/suprasellar location. Despite being a grade 1 tumor, there is high recurrence and endocrinal insufficiency. Malignancy arising in craniopharyngioma is extremely rare, has a dismal prognosis, and is currently not included as a separate entity in the World Health Organization Classification of Central Nervous System 5th edition. Here we describe a case of adamantinomatous craniopharyngioma and its malignant counterpart. The malignant part had unique histomorphology and basaloid cells with pseudoglandular architecture and a myxoid background. It bore a striking resemblance to adenoid cystic carcinoma. Both the benign and malignant counterparts were beta-catenin and SOX-2 positive, providing proof of the malignant part arising from the benign part. Tumors like squamous cell carcinoma and odontogenic ghost cell carcinoma have been described in cranipharyngioma. This case study is the first to describe this unique morphology of adenoid cystic carcinoma-like features. The possibility of adenoid cystic carcinoma was excluded by immunohistochemistry.