primary intracranial malignant melanoma ( pimm ) is a rare tumor of the central nervous system ( cns)2 ) . metastatic intracranial malignant melanoma ( mimm ) from cutaneous malignant melanoma ( cmm ) is a frequent occurrence . pimm is difficult to diagnose because pimm and mimm are similar in radiological and pathological appearance6,15 ) . on the other hand , extracranial metastasis of pimm is extremely rare . an 82-year - old women came to the department because magnetic resonance imaging ( mri ) , followed up every one year for asymptomatic cerebral infarction , showed mass lesion under the left cerebellar tentorium ( fig . 1 ) . one month later , on her admission , she had cerebellar symptoms such as nausea and gait disturbance , and the mass lesion showed as rapidly enlarged on the mri . the mass lesion with niveau formation and a maximum diameter of 5 cm showed high density on computed tomography ( ct ) , a slightly high intensity on t1 mri and a low intensity on t2 mri . 2-[fluorine-18]-fluoro-2-deoxy - d - glucose positron emission tomography / computed tomography ( fdg - pet / ct ) , chest and abdominal enhanced ct did not detect any malignant lesion such as an extracranial malignant melanoma ( fig . we performed a near total resection , but some residual tumor attached to the sigmoid sinus and the petrosal vein remained . a black solid and encapsulated nodular tumor was found under the left cerebellar tentorium and appeared to originate from the pia mater of the cerebellum ( fig . immunohistochemical examinations were positive for hmb-45 , melan - a and s-100 protein . the mib-1 ( ki-67 ) staining index was approximately 8% ( fig . we performed gamma knife surgery at a total dose of 21 gy for the residual tumor of the sigmoid sinus and the petrosal vein . an mri at 11 months after surgery showed local recurrence at the anterolateral edge of the left cerebellar tentorium . we performed gamma knife surgery at a total dose of 24 gy for the recurrent tumor . at 12 months , she experienced back pain , and vertebral metastasis was suspected after mri . therefore , fdg - pet / ct , chest and abdominal ct for a whole body examination was performed and showed multiple metastases in the left neck , the right latissimus dorsi muscle , the right collarbone , the liver , multiple vertebral bodies and the left thigh bone ( fig . 2 ) . recurrence in the brain and brainstem was difficult to distinguish in the fdg - pet / ct . her general condition continued to be good , and we performed an open biopsy for diagnosis of the tumor lesion in the right latissimus dorsi muscle . an 82-year - old women came to the department because magnetic resonance imaging ( mri ) , followed up every one year for asymptomatic cerebral infarction , showed mass lesion under the left cerebellar tentorium ( fig . 1 ) . one month later , on her admission , she had cerebellar symptoms such as nausea and gait disturbance , and the mass lesion showed as rapidly enlarged on the mri . the mass lesion with niveau formation and a maximum diameter of 5 cm showed high density on computed tomography ( ct ) , a slightly high intensity on t1 mri and a low intensity on t2 mri . 2-[fluorine-18]-fluoro-2-deoxy - d - glucose positron emission tomography / computed tomography ( fdg - pet / ct ) , chest and abdominal enhanced ct did not detect any malignant lesion such as an extracranial malignant melanoma ( fig . we performed a near total resection , but some residual tumor attached to the sigmoid sinus and the petrosal vein remained . a black solid and encapsulated nodular tumor was found under the left cerebellar tentorium and appeared to originate from the pia mater of the cerebellum ( fig . we performed gamma knife surgery at a total dose of 21 gy for the residual tumor of the sigmoid sinus and the petrosal vein . an mri at 11 months after surgery showed local recurrence at the anterolateral edge of the left cerebellar tentorium . we performed gamma knife surgery at a total dose of 24 gy for the recurrent tumor . at 12 months , she experienced back pain , and vertebral metastasis was suspected after mri . therefore , fdg - pet / ct , chest and abdominal ct for a whole body examination was performed and showed multiple metastases in the left neck , the right latissimus dorsi muscle , the right collarbone , the liver , multiple vertebral bodies and the left thigh bone ( fig . 2 ) . recurrence in the brain and brainstem was difficult to distinguish in the fdg - pet / ct . her general condition continued to be good , and we performed an open biopsy for diagnosis of the tumor lesion in the right latissimus dorsi muscle . these cells are found underneath the brain and the brainstem , inside the ventricles , at the optic chiasm , in the grooves of the various lobes , in the substantia nigra and in the choroid16 ) . it is not easy to differentiate pimm from mimm because they overlap in radiological and pathological appearance15 ) . it has been reported that the following factors are proposed for establishing a diagnosis of pimm : ( i ) no malignant melanoma outside the cns ; ( ii ) involvement of the leptomeninges ; ( iii ) intramedullary spinal lesions ; ( iv ) hydrocephalus ; ( v ) tumor in the pituitary or pineal gland ; and ( vi ) a single intracerebral lesion6 ) . , there were no skin or eye melanoma , neither the fdg - pet / ct or chest and abdominal enhanced ct detected malignant lesions in the other parts of her body . it has been reported that mimm often shows extensive necrosis , more obvious cytologic malignancy , a higher mitotic index and a higher mib-1 staining index . the mib-1 staining index of mimm ( range , 1738 per 10 hpfs ) was higher than that of pimm ( range , 215 per 10 hpfs)1 ) . the median survival for patients with mimm is only 56 months while patients with pimm survive 924 months . it has reported that of 168 cases with extracranial metastasis in adults 68 were cases of glioblastoma , 49 of meningeal tumors , 22 of medulloblastoma , and other cases were of ependymoma , pituitary gland , oligodendroglioma , neuroblastoma , germinoma and hemangioblastoma7 ) . the lungs , pleura , lymph nodes , bone , and liver are the most common sites of extracranial metastases of glioblastoma4,11 ) . risk factors for extracranial metastasis include previous craniotomy , ventricular systemic shunting , high - grade tumor histology , radiation therapy , long interval since the primary therapy and tumoral relapse 17 ) . in our case , the patient received craniotomy and some residual tumor attached to the sigmoid sinus and the petrosal vein remained . it is quite possible that the residual tumor invading the venous sinus and the dural sinus was the cause of the hematogenous dissemination . the most common sites of clinical presentation are the skin , subcutaneous tissue and lymph nodes followed by lung , liver and bone . it is quite possible that ct , mri , fdg - pet / ct and skeletal scintigraphy provide clinically useful information to detect the metastasis of cmm . especially , a whole body fdg - pet / ct is a non - invasive , high - resolution molecular imaging technique that can detect cmm metastasis based on abnormal cellular glucose uptake10 ) . however , fdg - pet / ct has limitations with small ( less than 1 cm ) , pulmonary and brain metastasis3 ) . on the other hand , the optimal time point for detecting metastatic malignant melanoma it has been reported that the optimal timing to perform fdg - pet / ct in high risk cmm is at 6 months after surgery because all recurrences at an early asymptomatic stage were found between 714 months after surgery 8) . in the case of pimm , therefore , we concluded that whole body fdg - pet / ct should also be performed to screen for extracranial pimm metastasis even at an early asymptomatic stage after surgery . although extracranial pimm metastasis is extremely rare , we should carefully follow up extracranial metastases together with intracranial ones , especially with fdg - pet / ct , even at an early asymptomatic stage .
we report a case of primary intracranial malignant melanoma ( pimm ) with extracranial metastases . 
 the patient was an 82-year - old woman diagnosed with pimm under the left cerebellar tentorium . 
 we performed a tumor resection followed by gamma knife surgery . 
 an magnetic resonance imaging at 11 months after surgery showed a local intracranial recurrence . at 12 months , vertebral metastasis was suspected , and 2-[fluorine-18]-fluoro-2-deoxy - d - glucose positron emission tomography / computed tomography ( fdg - pet / ct ) showed multiple extracranial metastases . 
 she died at 13 months after surgery . 
 although extracranial metastases of pimm are extremely rare , we should carefully follow up extracranial metastases together with intracranial ones , especially by fdg - pet / ct , even at an early asymptomatic stage .