Non- Hodgkin’s lymphoma of the cranial cavity may be present due to metastatic deposit of systemic lymphoma in 1-3 % cases and cranial vault alone rarely, but primary NHL of the cranial vault is rare. [1,2] Not more than 50 cases have been reported to date. Primary cranial vault lymphoma had been defined as localized lymphoma not involving other than the primary site for more than 6 months once the initial diagnosis is made.[3] In primary calvaria lymphoma, the most common histopathology reported is NHL large B-cell type (39-78%) and in primary Dural lymphoma most common pathology reported is marginal B cell lymphoma which is low grade.
In the meta-analysis by El Asri et al., average age at presentation was 60 years without any genderprevalence. The average duration of the onset of symptoms was 6 month. [4] In the present case report, the patient noticed swelling5 years back on the right parieto-occipital region which was of the size of grapes (nearly 2.5cm) but he was inflicted with COVID twice within 1 year at an interval of 6 months and there was a fast progression of size and patient noticed another 3lesions on the scalp. This fast progression, in this case, maybe attributed to immunosuppression caused by COVID 19 treatment as well as the immunosuppressive therapy he had received during his treatment as he developed a drastic fall in oxygen saturation of 80% in both the episode of COVID 19 infection. IN the study by El Asri et al and Ferreri et al immunosuppressed condition had been reported in nearly 11% of patients. [4,5]
In the present study tumor characteristics on T1 and T2 weighted MRI were almost similar to the other reported patients with similar histopathology and ithomogenously contrasted enhancing with Dural tail sign. We noticed selective permeation of tumor mass through the cranial vault with tumor deposit on the inner table of calvaria and seeding of the dura in the anterior frontal region causing mass effect and no visualization of the anterior sagittalsinus. On DSA tumor was being fed from bilateral ECA with tumor blush present suggesting vascular lesion and anterior sagittal sinus and left transverse sinus was also not visualized. Angiographic findings were more in favour of meningioma as lymphomas are not reported to have vascular blush on angiography. Lymphoma mimicking meningioma is very uncommon and 3-4 case reports are available in the literature. [3,6]
In our patient MRIfindings did not reveal any widening of diploic space, there were slightly cortical changes and patchy contrast enhancement suggestive of permeation of calvaria cortex by malignant lymphomatous cells. Anteriorsagittal sinus was not visualized probably due to overlying compression by tumor mass as well metastatic deposit through emissary's veins. As the lesion was high-grade permeation of left transverse sinus through emissary veinous channel leading to thrombosis may be the reason. Such selective permeation of malignant lymphomatous cells was reported in the study byOchiai et al and Galarza et al. [7,8] In the study by Kissling et al the lymphomatous mass resembling meningioma have diffuse osteolytic features with thrombosis of the posterior third sagittal sinus.[3]Such atypical radiological findings probably have not been reported which we felt need mentioning.
Faster progression of the tumor was reflected by high KI-67 proliferation index but one good prognosticfeature was the absence of BCL-2 staining which helps in good chemotherapy and radiotherapy response as reported in different studies.[9] In the previous, reported cases mimicking meningioma BCL-2 staining in FISH were presented suggesting a poor response to treatment. [3,8] In these reports long follow-up is not reported. In the study by Ciarpaglini et al high-grade lesions have survival extending from 10-17 months and in low grade lymphoma 5 year survival is around 40-50%. [10] Our patient although have developed a multicentric tumor in due course of time, lesstumour bulk and favourable histopathology for chemo & radiotherapy had given the advantage of better survival and he is presently asymptomatic after treatment on 5 months of follow up and no fresh lesion on repeat MRI.
Patients having cranial vault primary having benign course may convert into aggressive lesion following infliction with the immunosuppressed state as in present patient study and it may present as a diagnostic dilemma but early excisional diagnosis together with favourable immunostaining with BCL-2 may add survival benefits. We thought to report this case due to unusual association with COVID 19 as well atypical presentation which was not reported in the earlier reported case which put us as in diagnostic and management dilemma.