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meningioma is the most common type of benign brain tumor , whereas ectopic meningioma , although reported , is rare .
the head and neck region is the most common ectopic site whereas the scalp , skin , orbit , paranasal sinuses , salivary glands , and intraosseous or intradiploic regions can also be affected [ 25 ] . in view of their rarity , ectopic meningiomas of the skull
the main differential diagnoses are fibrous dysplasia and osteoid osteoma , the most common being benign primary tumors .
we report herein the case of a 62-year - old female patient with a pure ectopic intraosseous meningioma without dural invasion .
a 62-year - old female patient presented with a history of classical migraine for the last 30 years .
six month before the diagnosis , her headaches had changed their characteristics to a continuous unilateral ( right side ) pain of increasing intensity .
the patient reported no nausea or vomiting , which usually followed her typical migraines . also , the patient noted a growing lump on the right parietal side and was referred to our service by her primary care physician . on neurological examination , the patient was alert and oriented , complaining of moderate headache .
a hard , slightly painful , elliptical prominence without clearly defined margins was detected on her right parietal bone , which measured approximately 7    8  cm .
mri images showed an osteoblastic lesion in the right parietal bone diploe , with possible involvement of both cortical layers and without dural extension ( fig .
the patient was scheduled for elective surgery in the following week . the surgical procedure consisted of a right parietal incision and craniotomy and
craniotomy was performed with a clear 1-cm margin and skull convexity was reconstructed with a titanium mesh ( fig .
ten months after surgery , the patient remains asymptomatic and shows no signs of recurrence ( fig .
ectopic intraosseous meningiomas can also be described as intradiploic or calvarial   and may appear as osteoblastic , osteolytic lesions [ 4,1014 ] or mixed lesions   on plain x - rays and computed tomography scans .
further investigation by mri can identify ectopic meningiomas , which do not exhibit the usual paramagnetic contrast enhancement .
the clinical presentation of the present case is similar to that found in previously reported cases of skull tumors , usually headaches and an often painless , palpable mass on the scalp or skull .
involvement of other ectopic sites such as the paranasal sinuses and orbit usually manifests as pain and proptosis , whereas pain and a palpable mass are common when the tumor affects more distant sites .
histologic examination usually presents meningothelial meningiomas , but the microcystic   or lipomatous   variations are also reported .
immunohistochemical staining is usually positive for progesterone receptor , epithelial membrane antigen as in our described case , and s100 . in 1960 , hoye et al .  
reviewed the latest case reports and proposed the classification of ectopic meningiomas into four types : ( 1 ) intracranial tumors with extracranial extension ; ( 2 ) meningiomas originating in cranial nerve sheaths ; ( 3 ) extracranial tumors without any connection to cranial nerve foramina ; ( 4 ) intracranial benign lesions with extracranial metastases . in 2000 , lang et al .   described a similar , but simpler classification : type 1 , purely extracalvarial tumors ; type 2 , purely calvarial tumors , and type 3 , calvarial tumors with extracalvarial extension .
each type is further divided according to location into skull base ( s ) or calvarial ( c ) lesions .
our case is classified as type 3 in hoye s classification and type 2 in lang s classification , since the lesion was restricted to the skull ( inner and outer tables ) , showing no dural invasion on histopathological examination , supporting the hypothesis that the tumor originated in the diploe layer .
some theories have been offered to explain how a meningioma can appear distant from the usual arachnoid cap cells ( meningocytes ) .
one theory suggests that embryological remains of neuroectodermal tissue , which should develop into cap cells , can expand   or erroneously migrate to other tissues .
other theories that could account for some cases are the spreading of these remnant cells due to trauma , dural lesions , or cells entrapped in cranial sutures and cranial nerve sheaths .
some authors proposed the occurrence of dedifferentiation of cells in extracranial tissues , which develop into neoplastic meningocytes .
none of these theories could be confirmed in the present case , but a probable intradiploic origin is suggested .
overall , most meningiomas , including ectopic tumors , are benign ; therefore , their complete surgical excision should be the rule .
partial resection of residual lesions can be monitored radiologically , while adjuvant therapies such as radiation may provide an alternative for symptomatic and surgically difficult cases .
written informed consent was obtained from the patient for publication of this case report and accompanying images .
a copy of the written consent is available for review by the editor - in - chief of this journal .
written informed consent was obtained from the patient for publication of this case report and accompanying images .
rbv : drafted and designed the manuscript and participated in surgery ; pthf : drafted and coordinated the manuscript ; rll : participated in surgery and reviewed the literature for previous cases ; vzm and fol : analyzed the pathological and histological materials ; frr : coordinated surgery and grammatical review .
highlightsintraosseous meningiomas may be confused with fibrous dysplasia and/or osteoid osteoma.lesions appear either as osteoblastic or osteolytic lesions.usually presents as a painless palpable mass associated with headaches.embryological remnants of neuroectodermal tissue or cellular dedifferentiation seem to justify the lack of dural connections.complete surgical excision is usually curative .