Eosinophilic Granuloma of the Skull Vault: A Case Report.
- *Corresponding Author:
- Domenico Gerardo Iacopino
Department of Experimental Biomedicine and Clinical Neurosciences
School of Medicine, Neurosurgical Clinic
University of Palermo, Via del Vespro 129
90100, Palermo, Italy
E-mail: [email protected]
Background: Eosinophilic granuloma is the benign form of Langerhans cell histiocytosis, a rare proliferative disorder. Skull osteolytic lesions are quite frequently encountered.
Case report: We report the case of a 16 year old boy who was admitted to our Department with a painful swelling left frontal mass. A diagnosis of eosinophilic granuloma was presumed on the basis of the neuroradiological findings. Surgical removal of the lesion was achieved and the bone defect reconstructed by autologous fibrin glue and a titanium mesh. Histopathology confirmed the diagnosis.
Conclusion: Although uncommon, eosinophilic granuloma should be considered in the differential diagnosis in case of an osteolytic calvarial lesion.
Eosinophilic granuloma, Langerhans cell, Calvarial bone
EG: Eosinophilic Granuloma; LCH: Langerhans Cell Histiocytosis; CT: Computed Tomography; MRI: Magnetic Resonance Imaging
Eosinophilic granuloma (EG) is the mildest form of Langerhans cell histiocytosis (LCH), a rare proliferative disorder of Langerhans type histiocytes with an unknown etiology. EG predominantly affects children, adolescents and young adults. Its skeletal manifestations most often involve flat bones, with more than 50% found in the skull, spine, mandibula, ribs and pelvis . Bone lesions have varied and nonspecific radiographic appearances. Eosinophilic granuloma generally follows a benign clinical course . The two main prognostic factors for the disease are patient age and extent of organ involvement. Bone lesions can be treated conservatively after biopsy to confirm the diagnosis . Additional local therapy may be used for painful lesions, lesions with a risk of pathological fracture, or unacceptable dysfunction or deformity.
A 16 year old boy was referred to our Institution, complaining of several months history of frontal headache. He was alert and conscious, without neurological deficits. On general examination a tender, painful, left frontal mass was found. Routine blood tests and chest X-rays were unremarkable. Head computed tomography (CT) scan showed a single, left frontal, sharply round, osteolytic lesion without marginal sclerosis. Brain magnetic resonance imaging (MRI) confirmed a T1 isointense, slightly T2 hypointense cranial vault lesion (Figure 1). A diagnostic hypothesis of eosinophilic granuloma was made. A whole body CT scan was performed to rule out multisystemic involvement. Indication for surgical approach was justified by severe headache and shared apprehension about a lytic skull lesion: complete excision was obtained, the dura mater was found intact and the bone defect was covered with titanium mesh plate and autologous fibrin glue [4-7]. The patient recovered without complications and was discharged home within few days. Histological examination confirmed the hypothesis of an eosinophil granuloma. The patient underwent clinical and radiological follow up that showed neither residual disease nor recurrence also after 1 year.
Figure 1: Radiological aspect of an eosinophilic granuloma of the skull vault. In the red circle, the lesion is highlighted: The CT scan shows the typical lytic lesion with involvement of both inner and outer table, without sclerotic rim. On MRI, the lesion appears isointense in T1 images and slightly hypointense in T2 without dural involvement
Langerhans Cell Histiocytosis (LCH), previously known as histiocytosis X, is a rare proliferative disorder of bone marrow-derived antigen-presenting cells, whose clinical manifestations vary from a multisystem disease with organ dysfunction to solitary eosinophilic granuloma (EG). The role of genetic or immune system in the pathogenesis seems to be less understood as compared to other diseases [8-12]. The natural history and prognosis of LCH are highly variable, depending on the patient’s age and involvement of vital organs such as liver, lungs, spleen, or hematopoietic system . Eosinophilic granuloma is the benign form of three clinical variants. It is characterized by single or multiple skeletal lesions, characterized by proliferation of Langerhans cells with an abundance of eosinophils, lymphocytes and neutrophils that produce prostaglandins determining medullary bone resorption. It predominantly affects children, adolescents and young adults, with a male to female ratio of 2:1. Any bone can be involved, the more common sites being skull, mandible, spine, ribs and the long bones. The lesions may be asymptomatic and discovered incidentally. More often, the patient refers a tender, painful mass during several weeks to several months before diagnosis. Systemic symptoms may also be present, including general fatigue and, more rarely, fever with leucocytosis. Laboratory findings are generally normal except for rare cases of eosinophilia . On standard X-rays EG appears as a punched out lytic lesion without sclerotic rim; it may show a double contour or a bevelled edge due to greater involvement of the inner more than the outer table. On CT scan it can be better appreciated the cortical erosion and the soft tissue involvement. At MRI, T1 images typically show low signal, on T2 it can be isointense or hyperintense; contrast enhancement can be present . Differential diagnosis of a solitary lytic skull lesion in a child or young adult includes epidermoid or dermoid cysts, as well as other benign and malignant skull tumours such as osteoblastoma, haemangioma or osteogenic sarcoma.
Treatment for calvarial EG has classically involved excision of the lesion or curettage, depending on the size of the defect. Spontaneous healing of EG in other sites has been reported, but most calvarial lesions are immediately referred for excision. Oliveira et al. reported 4 cases of spontaneous disappearance of calvarial EG: the lesions increased in size initially and then became smaller and disappeared within 3–4 months [16,17]. More recently De Angulo et al.  described 8 cases of skull lesions that were managed conservatively: only one patient needed resection because of persistent pain and slight growth of the lesion. What have been postulated is that the chances of spontaneous remission of EG are higher in skeletally immature patients than in mature patients . Conservative approach may have a fallback for lacking histological diagnosis, considering that these kinds of lesions include many benign as well as malignant conditions.
Eosinophilic granuloma is a benign disorder that affects children and young adults, particularly males. The clinical and radiographic findings are often not specific enough to determine the diagnosis. Nevertheless, CT scan and MRI play an important role in determining osseous perforation and the presence of extradural or extracranial soft-tissue mass. For symptomatic single skull lesions, surgical excision remains the main treatment option.
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