Discussion
WM is a rare hematologic malignancy accounting for 1-2% of monoclonal
gammopathy and
associated to lymphoplasmacytic lymphoma in the WHO classification [9,
10]. This B cell lymphoproliferative disorder is defined by the
infiltration of lymphoplasmacytic cells into bone marrow and the
demonstration of immunoglobulin M monoclonal gammopathy [4, 8].
Neurologic symptoms occurring in 25% of cases are commonly related to
serum hyperviscosity or autoimmunologic phenomena [8]. However, a
malignant infiltration of the CNS by lymphoplasmacytic cells remains
extremely rare and defines Bing-Neel syndrome. Two Danish physicians
namely Jens Bing and Axel Valdemar Neel first demonstrated this
exceptional condition in 1936 [7, 8]. According to a literature
review, there was only 33 cases of BNS until 2010 on Pubmed. Simon et al
reported 44 cases of BNS in a multicenter study and gave a literature
review of 33 cases from 1995 to 2014 [11]. However, this last decade
(2015 to 2024) showed a great interest for BNS With 105 cases found on
Pubmed research out of 154 reported. so far. BNS consists in either
diffuse or tumoral form as in our case [1, 2, 4, 7, 8]. Tumoral BNS
is often consistent either with intraparenchymal process suggestive for
glioma, or meningeal infiltration [8, 9]. Thus, extra axial
appearance is very rare and, to the best of our knowledge, only 3 cases
of BNS mimicking meningioma are reported in the literature and our case
displays the biggest size [6]. The clinical presentation of the
tumoral BNS is similar to other space occupying lesions and usually
consists of focal deficit or seizure [1, 2, 8, 9, 10]. Diffuse BNS
often presents with headache, memory loss, confusion, dementia or coma
[1, 4, 8, 10]. In our case, the patient was paucisymptomatic despite
the large size of the tumor and let foretell a long duration of
evolution. BNS can occurred at any time during the course of the disease
[12]. In a study of 34 cases of BNS, Castillo et al noticed this
occurrence in half of WM cases within 5 years and in 18% over 10 years
[12]. Fintelmann et al classified BNS into 2 categories: group A
describes patients with neurologic symptoms probably as a result of
lymphoplasmacytoid cells within the central nervous system (parenchyma,
meninges, CSF and dura); Group B refers to BNS cases with neurological
symptoms without cells (< 5 cells/mm3)
within the CSF [13, 14]. Our patient may be classified as group A
and some authors suggested a more important damage of
blood-brain-barrier allowing the transfer of these cells from the blood
to the central nervous system in this group [13, 14]. The diagnosis
of tumoral BNS is based on the pathological examination of the tumor and
the bone marrow biopsy associated to protein electrophoresis [1, 2,
6]. This pathological examination often demonstrates atypical lymphoid
cells consisting of small lymphocytes, lymphoplasmacytic cells and
plasma cells [1, 2]. Immunohistochemically, these BNS cells are B
cells usually positive to CD20, CD138 and negative to CD5, CD10, CD23
[2, 7, 10]. These cells express immunoglobulin M and serum proteins
electrophoresis always shows an Ig M monoclonal gammopathy [1, 2,
8]. All those pathological and proteins immunoelectrophoresis features
were found in our patient. The authenticity of our presentation is
highlighted by the radiological presentation. Indeed, all but three of
the Bing-Neel tumors were intra-axial lesions [6, 8]. The first
extra-axial tumoral BNS mimicking meningioma was reported by Civit et al
in 1997 [3], the second and third was reported in 2020 and 2023. Our
observation is the fourth and We failed to find a most voluminous than
this latter in literature review. Because of their intra-axial location
and their relatively small size, some Bing-Neel tumor requires only
stereotaxic biopsy for histological confirmation [9]. In our case,
the radiological diagnosis of the lesion was consistent with a giant
meningioma, thus the surgical approach was justified. The treatment of
tumoral BNS is based on chemotherapy, which might be associated to a
focal radiation therapy [1, 2, 6]. WM shows an estimated median
survival of 7-12 years, albeit BNS prognosis was still severe with a
free survival rate of 12 months (0-84 months) despite a heavy
therapeutic armamentarium [14, 6]. However, the outcome of tumoral
BNS seems to be better than diffuse BNS [6] and more recent study
revealed a survival of 5 years and 10 years of 71% and 59% [11,
14]. Castillo et al identified in univariate analysis, age above 65
years, previous treatment for WM and platelet count < 100 x
109/L as adverse prognostic factors [12]. None of
these latter were found in our patient and he was asymptomatic a
eighteenth month follow up.