Unusual presentation of sarcoidosis: solitary intracranial mass lesion mimicking an intracranial neoplasm: a case report

Sarcoidosis is a multisystem disease of unknown cause and with a worldwide distribution. Involvement of the central nervous system occurs in a relatively small number of patients with sarcoidosis. Isolated neurosarcoidosis without signs of systemic disease however is a rare. In this report, we present an unusual case of neurosarcoidosis with intra cranial mass mimicking radiologically a glioma. Pathological examination revealed intraparenchymatous necrotising granulomatous lesions. After clinicopathological correlation, the diagnosis of a necrotizing cerebral granulomatosis (neurosarcoidosis) with atypical systemic involvement was made. Because of its non-specific clinical presentation and neuroradiological imaging characteristics, intracranial neurosarcoidosis remains a very difficult diagnosis, particularly in the absence of systemic signs of the disease.


Introduction
Necrotizing granulomatous lesions of the central nervous system (CNS) are aetiologically diverse. These include chronic infections such as fungal or mycobacterial, as well as non-infectious causes such as Wegener granulomatosis, idiopathic pachymeningitis and neurosarcoidosis of the necrotizing sarcoid granulomatosis variant.
An accurate diagnosis is critical to deciding the optimal treatment strategy, which can be diametrically opposite (intensive antimicrobial regimen vs immunosuppressants). Therefore a systematic thorough diagnostic work-up, clinicopathological correlation and appropriate follow-up are essential elements of patient management [1,2].

Patient and observation
A 32-year-old Tunisian woman presented with 2 years history of headaches. The patient"s past medical history was no significant.
She did not have a history of sinusitis, nasal deformity, or oral ulcers. she was not on any regular medications. Routine laboratory tests including renal function were normal. Chest x-ray showed neither lung lesions, nor mediastinal lymphadenopathy.
After an initial CT scan showed a left temporal lobe mass, he was Trichrome staining ( Figure 6). There was no definitive vasculitis, although some vessels had inflammatory cells around them.
Sections were stained with periodic acid-Schiff and did not reveal any fungal organisms. Stain for mycobacteria (Zeihl-Neilsen) was negative.
Based upon the histopathology of the resected mass lesion, the two main differential diagnostic considerations were a mycobacterial infection (likely tuberculosis) and sarcoidosis. However, negative special stains, negative skin test for tuberculosis and normal Chest x-ray, nearly ruled out an infectious aetiology.
Postoperatively, the patient underwent corticotherapy. She had a partial motor deficiency of the right hemibody due to the achievement of the internal capsule. She is currently being retraining and she will have a fruther control.

Discussion
Sarcoidosis is an idiopathic, complex, multisystem inflammatory disease of unknown aetiology, characterised by non-caseating [3]. It has been described in patients of all ages (usually under 50 years), sexes (more in women) and races. However, Americans and Africans are affected more often and tend to have a more severe and chronic disease, likely related to genetic associations within the human leukocyte antigen region [1,4]. The clinical course is characterized by episodic exacerbations that are self-limited and may or may not respond to immunosuppressive therapy [2].
Imaging studies are nonspecific, revealing a poorly defined mass with a variable degree of surrounding edema. Thus, in the appropriate clinical setting, neurosarcoid should be included in the differential diagnosis of a CNS mass [2,8] Intramedullary involvement occurs in up to 25% patients [5,9]. The cavernous sinus is rarely involved in neurosarcoidosis.
Although the wide spectrum of imaging findings in neurosarcoidosis is well documented, there is a paucity of data to show concordance between imaging findings and clinical information, the expected evolution of imaging abnormalities with immunosuppressive therapy, and the possible prognostic significance of imaging features [5].
Abnormal laboratory findings such as pancytopoenia and elevated serological findings such as C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and angiotensin-converting enzyme (ACE) levels, are all non-specific(BMJ2011). Lumbar puncture is useful in ruling out other neurological disorders, in particular infectious, but cerebrospinal fluid findings are not specific [7].
Despite the varied clinical and radiological appearances, the histopathologic hallmark of sarcoidosis is the presence of sarcoidal granulomas.
Sarcoidal granulomas, often described as "tight" granulomas, are discrete, round to oval, and composed of epithelioid histiocytes and multinucleate giant cells which may be of either Langhans or foreign body type. Generally, the type of multinucleate histiocyte present in a granuloma is not helpful in arriving at a specific histological diagnosis. Giant cells may contain asteroid bodies, conchoidal bodies (Schaumann bodies), or crystalline particles. Typical granulomas are surrounded by a sparse rim of lymphocytes and plasma cells, and only occasional lymphocytes are present within them. Consequently, they have been described as having a "naked" appearance. Although the granulomas may be in close proximity to one another, their confluence is not commonly found. With reticulin stains, a network of reticulin fibers is seen surrounding and permeating the histiocytic cluster. The classic sarcoidal granuloma, compared with other types of granulomas, is relatively devoid of central necrosis (non-caseating granulomas). An accompanying granulomatous vasculitis may be apparent [10].
Necrotizing sarcoid granulomatosis, initially described by Liebow in 1973 (9), has been described even less frequently than its non necrotizing counterpart. Since that initial report, a few cases involving the central nervous system with histologic confirmation, have been reported in the literature [2]. The necrosis of Wegener"s also often creates geographic patterns and may be surrounded by palisading histiocytes. NSG patients typically have a long clinical course with a significant, favorable response to steroids. These features clearly rule out infectious causes, particularly when supported by negative cultures [2,6].
The management of neurosarcoidosis is not standardised.
Immunosuppressive therapy may be interesting and should be initiated with corticosteroids. Other immunosuppressive drugs should be added in severe cases or after frequent recurrences. Its prognosis cannot be easily predicted. Natural outcome is poor.

Conclusion
The diagnosis of neurosarcoidosis remains in the purview of clinical suspicion. Unlike systemic sarcoidosis, there is difficulty in making tissue diagnosis when involvement of CNS is suspected. MRI studie is sensitive in the detection of CNS inflammation but lack specificity, making the ascertainment of neurosarcoidosis a clinical challenge.
In addition the low prevalence of the disease makes clinical trials difficult and therapeutic decisions are likely to be made from careful reporting from case studies.