eosinophilic granuloma ( eg ) , a benign local bone disease , is classified as the mildest form of langerhans ' cell histiocytosis ( lch ) .
eg predominantly affects children , adolescents , and young adults , and the skull is the most common site of involvement.5 ) the pathologic diagnosis of eg can be confirmed by positive stains of cd1a antigen and protein s-100 or when intracytoplasmic organelles ( birbeck granules ) are detected using electron microscopy.11 ) the most common symptom of eg is a tender , growing scalp mass , but it can be asymptomatic and incidentally found on skull x - rays . the clinical course is benign with a tendency to spontaneous regress ; however , eg may also recur .
it is common to prove the antecedent of a mild head trauma preceding clinical symptoms .
a-6-year - old boy was referred to our hospital with a soft mass on the midline of his forehead .
he had undergone surgery for eg in the vertex 19 months ago ( figure 1 ) .
one month prior to minor head trauma , a follow - up computed tomography ( ct ) ( figure 2 ) was performed to check for recurrence , and none was found .
one week before his arrival at the hospital , he had hit his head , and the resulting mass grew rapidly after the trauma .
the findings of the neurological examination were unremarkable , except for a non - tender , soft , and immobile mass .
the three - dimensional ( 3d ) ct showed a lytic bony defect on the frontal bone without hemorrhage ( figure 3a and b ) and the enhanced magnetic resonance imaging ( mri ) revealed a 1.4 cm - sized growing mass on the midline of the forehead ( figure 3c and d ) .
the level of erythrocyte sedimentation rate ( esr ) and c - reactive protein ( crp ) was within normal limits .
the protruding mass extended from the scalp through the defect in the frontal bone , and was visualized when the scalp flap was reflected ( figure 4a ) . after removal of the bone flap and tumor , it was noted that there was no hematoma and the dura mater was intact without invasion ( figure 4b ) .
the tumor was removed completely and the bony defect was replaced with bone cement ( figure 4c ) .
the histopathological examination revealed numerous oval langerhans ' cells and eosinophils ( figure 5a and b ) .
the langerhans ' cells were stained for cd1a and s-100 ( figure 5c and d ) .
the patient was followed - up six months after the operation and had a normal neurologic examination at that point .
lch is a unifocal or multifocal disorder of the bone or soft tissue , most often appearing as a lytic lesion of the skull .
eg is the mildest form of lch.5 ) the exact incidence of eg is not well known but vandenberg and coley12 ) found that it accounted for only 2.4% of benign skull tumors . in the series of cases studied by jelsma and ross,4 )
the most common symptom of eg is a tender , enlarged scalp mass on the parietal and frontal bones .
eg may be asymptomatic and only discovered on a skull x - ray by chance .
the x - ray radiologic findings consist of a punched - out , skull lesion with sharply defined margins .
as the clinical and radiologic findings are not specific enough to determine the diagnosis , cytology is very helpful in diagnosing eg .
the key feature is the identification of characteristic langerhans cells in a background of eosinophils and red blood cells.5 ) there is no definite disease etiology for eg .
however , autoimmune diseases , inflammatory processes , and uncontrolled langerhans cell replication can be considered to be etiological factors.3 ) also , minor trauma is considered an etiologic factors .
there have been six reported cases of eg associated with epidural hematoma ( table 1).1678910 ) the possible mechanisms of epidural hematomas in the six cases consisted of a rupture of the tumor cyst , communicating with the epidural vein and the sinus pericranii , or a head trauma - related intratumoral hemorrhage , which subsequently penetrated into the epidural space .
all six cases were associated with epidural hemorrhages , while our case was not . in our case ,
no hematoma or hemorrhage was found in the ct / mri image , or in intraoperative and pathologic findings .
the patient in our case regularly visited the clinic for follow - up appointments due to his history of eg .
the ct scan taken one month prior to the trauma showed no definite recurrence ; however , a newly developed eg lesion was found one week after the trauma .
this indicates that the development of eg may be associated with trauma . in this case
, it is thought that eg developed through a local inflammatory response due to a minor trauma .
trauma may be a trigger factor of the inflammatory response instead of the etiology of the disease .
the elevated levels of esr and crp are found in some , but not all , cases of eg .
this is because eg lesions are limited to local level and the time between diagnosis and trauma varies . in the present case
, the author finds the period between the trauma and diagnosis to be relatively long .
factors related to hematoma formation may include the trauma 's intensity and the time interval after the trauma .
for example , in one case , a patient with an epidural hematoma had a two - week time interval , with a fluid level confirmed four weeks later . in the management of solitary eg , surgical excision is recommended and radiotherapy can be considered as an adjuvant therapy if necessary .
some authors advocate surgical excision followed by postoperative treatment that includes low - dose radiotherapy , intralesional application of corticosteroids , or a combination of chemotherapy and radiotherapy.11 ) other studies found that solitary calvarial eg in skeletally immature patients 14 years of age or younger resolved fully without any recurrence.2 ) eg is responsive to steroid treatment and this indicates that the etiology of eg is associated with local inflammatory processes . to avoid surgical procedures ,
the prognosis depends on the age of the patient at the time of diagnosis and the number of lesions .
the local recurrence rate is 6% , and new lesions appear in about 22% of patients , therefore , long - term follow - up is recommended.311 )
our case suggests that minor trauma may be an aggravating factor for the progression of eg , based on the radiological findings before and after the trauma .
thus , careful observation with regular follow - up is needed for patients with eg after trauma .
 the authors present a case of rapidly progressing eosinophilic granuloma ( eg ) of the skull without hemorrhage after minor trauma . 
 a 6-year - old boy presented with a soft mass on the midline of his forehead . 
 he had a surgery for eg 19 months ago . 
 one month earlier , computed tomography ( ct ) and bone scans were performed to evaluate the possible recurrence of eg , and there was no evidence of recurrence in ct . however , a slightly increased uptake in the bone scan was noted on the midline of the forehead . a rapid growing mass developed in a new spot after a minor trauma 7 days before the patient arrived at the clinic . 
 his physical examination was unremarkable , except for a non - tender , soft , and immobile mass . 
 a plain skull x - ray and ct showed a lytic bony defect on the midline of the frontal bone . 
 magnetic resonance imaging showed a 1.4 cm sized enhancing mass . surgical resection and cranioplasty 
 were done . 
 the role of trauma in the development of eg is unclear . 
 however , our case suggests that minor trauma is an aggravating factor for eg formation . 
 careful observation with regular follow - up is necessary in patients with eg after minor trauma . 
Introduction
Case Report
Discussion
Conclusion