craniopharyngioma is a type of benign tumor that arises from rathke s pouch , a derivative of the oral ectoderm , and accounts for approximately 33.5% of all intracranial tumors3 ) . although regarded as a world health organization ( who ) grade i tumor , it often demonstrates aggressive local behavior after surgery and requires adjuvant radiotherapy . craniopharyngiomas are known to recur even after presumed total resection , especially at the primary site or in its vicinity , suggesting microscopic residual disease . it has been estimated that the recurrence rates after total and subtotal resection are 30% and 5070% , respectively . craniopharyngioma rarely undergoes malignant transformation , a phenomenon that was most likely first described by salyer in 197310 ) . the etiology and pathogenesis of malignant transformation is unclear , although previous literature has suggested a correlation with radiotherapy9 ) . the prognosis of malignantly transformed craniopharyngioma is poor and because of its low incidence rate , there is insufficient evidence for various treatment modalities . herein , we report a case of craniopharyngioma with subsequent malignant transformation 2 years after the first operation . a 26-year - old male patient presented with a 1-week history of progressive headache and visual disturbance without any other neurological deficits . brain magnetic resonance imaging ( mri ) revealed a suprasellar mass lesion with enhanced solid and multiseptated cystic components measuring 3.02.8 cm ( fig . preoperative investigations of pituitary function including prolactin and thyroid function did not reveal any abnormalities . the patient underwent an excision via an interhemispheric transcallosal approach with near - total resection of the tumor . 2 ) . there was no cytologic atypia and mitoses . in the immediate postoperative period , after 6 months , mri showed a residual mass enhanced along the right anterior margin of the third ventricle floor ( fig . the patient was treated with medication for endocrine dysfunction and refused radiation therapy for the residual tumor . two years after his first operation , the patient presented to our department with confused mental status and progressive visual disturbance with bitemporal hemianopsia . mri showed a recurrence of a multiseptated cystic mass measuring 4.75.0 cm in the suprasellar cistern , third ventricle , and parts of the lateral ventricles ( fig . he was operated on via an interhemispheric transcallosal approach along the previous incision , and gross total resection of the tumor was performed . macroscopically , the tumor was soft and calcified with relatively defined boundaries compared to the surrounding tissue . immunological tests showed overexpression of p53 and ki67 ( ki67 labeling index 15% ) ( fig . 5c , d ) , and the tumor cells were positive for pancytokeratin and vimentin ( fig . the patient s symptoms of headache and impaired consciousness improved but the endocrine dysfunction and visual disturbances persisted . after three months , mri showed no residual tumor ( fig . 6 ) . however , seven months after the second operation , he visited the emergency room ( er ) with a high fever , general weakness , and drowsy mentality . while being evaluated in the er , he showed a sudden drop in blood pressure and expired shortly after despite immediate efforts to resuscitate him . no autopsy was performed . malignant transformation of craniopharyngioma is extremely rare and is not included in the current who classification of tumors of the central nervous system published in 20077 ) . malignant craniopharyngiomas are presumably derived from the remnants of rathke s pouch , which was first described by akachi in 19871 ) . a total of 23 cases have been reported since then and only five cases exhibited malignant craniopharyngioma without radiotherapy . four of these cases developed de novo ( primary type ) and only one case developed by malignant transformation of craniopharyngioma ( secondary type ) as in the present case ( table 1 ) . according to the literature , the pathologic findings of malignant craniopharyngiomas are heterogeneous including squamous cell carcinoma , myoepithelial carcinoma , ameloblastoma , ameloblastic carcinoma , and malignant craniopharyngioma mimicking odontogenic ghost cell carcinoma . a case of malignant craniopharyngioma with spindle cell proliferation that presented with sarcomatous transformation although diagnostic criteria for malignant craniopharyngioma have not yet been established , the following histology is suggestive of malignantly transformed craniopharyngioma : increased cellularity , nuclear pleomorphism , increased mitotic activity or ki67 proliferation indices , necrosis , or vascular proliferation . our case is similar to the case reported by wang et al.11 ) in that , the malignantly transformed portion was derived from the stromal spindle cell portion of the preexisting craniopharyngioma . there are various causes of malignant transformation in craniopharyngioma ; however , the exact mechanism is currently unknown because of the limited number of reported cases . according to the 13 case reports in the literature , radiotherapy might have an influence on malignant transformation . similar to our case of malignant transformation without radiotherapy , gao et al.4 ) reported histopathological confirmation of papillary craniopharyngioma after the patient s first surgery , followed by histopathological confirmation of adamantinomatous craniopharyngioma with ameloblastic carcinoma due to regrowth of the mass in some areas after the second surgery . after one year , the patient underwent a third surgery owing to recurrence and histopathological examination showed clear malignant features . in our case , the patient was diagnosed with a typical adamantinomatous craniopharyngioma during the first surgery ; however , after the second surgery , histopathological examination showed malignant features and confirmed that the craniopharyngioma was of the adamantinomatous type . therefore , other factors besides radiotherapy might contribute to malignant transformation of craniopharyngioma . recurrence of craniopharyngioma within a short period , especially after radiation therapy , could result in its malignant transformation .