Clinicopathological features of malignant transformation of craniopharyngiomas

Abstract

Objective To study the clinicopathological features of malignant transformation of craniopharyngioma. Methods Two cases of craniopharyngioma with malignant transformation were operated in Beijing Tiantan Hospital, Capital Medical University and were confirmed at Beijing Neurosurgical Institute during the period from January 2015 to December 2016, whose clinical data and histopathological features were retrospectively analyzed. The histological features of 1 case were compared before and after appearance of malignance. The immunohistochemical results of the malignant cases were compared with those of 10 cases of ameloblastic craniopharyngioma enrolled to the study during the same study period. Results The 2 cases with malignant transformation included 1 male and 1 female, and they were both 25 years old. They had both received radiotherapy before malignant transformation. They were both ameloblastic craniopharyngioma and squamous cell carcinoma before and after malignant transformation, respectively. After malignant transformation, large hyperchromatism nuclei with clear nucleolus, increased nuclear-cytoplasmic ratios, and increased mitotic activities were seen in the malignance. The tumor cells were arranged in solid sheets, and the stellate reticulum was rare. The wet keratins were frequently found in the cancer nests and in the stroma. The tumor cells infiltrated the brain tissue. The basement membranes were destroyed or disappeared. Compared with the pre-malignance, the tumors had higher cell density, more cellular polymorphism and more mitotic activity. All cases showed immunoreactivity for CK and CK5/6. Compared with the pre-malignant condition, the Ki-67 index was significantly elevated after appearance of malignance(50% vs.5%). The Ki-67 indexes of malignant transformation were significantly higher than those of ameloblastic craniopharyngiomas(50% vs.2%~10%). Conclusion The malignant transformation of craniopharyngioma seems to have an obvious malignant tendency, but it may still keep some features of craniopharyngioma, which is helpful for the differential diagnosis with similar tumors. Key words: Craniopharyngioma; Pathology; Diagnosis, Differential; Malignant transformation