Calvarial Lymphoma Presenting with Unusual Scalp Swelling

Sir, Primary lymphoma of bone (PLB), a rare hematological malignancy arising in the skeletal system, constitutes approximately 5% of extra-nodal lymphomas, less than 1% of all non-Hodgkin lymphomas (NHLs), and 3%–7% of all malignant bone tumors. The majority of them involve the pelvis, limb bones, mandible, and scapula.[1] Primary non-Hodgkin’s lymphoma involving the calvarium is a rare neurosurgical entity. We present a case of primary calvarial lymphoma in a young male patient who presented with headache and left-sided scalp swelling. A 24-year-old non-immunocompromised male patient presented with a history of left-sided headache and painless progressive swelling over the left side of the scalp since 4 months. General examination did not reveal any lymphadenopathy. Neurological and other systemic examination was normal. Local examination revealed firm, non-tender swelling with normal skin over the surface of the swelling over the left frontoparietal region [Figure 1a and 1b]. Computer tomography (CT) scan of the brain revealed extra axial mass lesion over the left high frontoparietal region extending up to the midline with areas of erosion of frontal and parietal bone with overlying scalp swelling which was enhancing post contrast administration [Figure 2a]. Magnetic resonance imaging (MRI) showed a large intracranial, extra axial lesion measuring approximately 10 cm × 9 cm × 4 cm in size involving primarily the left frontoparietal bone and overlying subcutaneous tissue. The lesion was isointense on T1 weighted imaging [Figure 2b] and hyperintense on T2 weighted imaging [Figure 2c and Figure 3a] with heterogeneous contrast enhancement [Figure 3b]. It extended superiorly to involve the superior sagittal sinus for about 5.5 cm in length. Digital subtraction angiography showed moderate diffuse tumor blush from left middle meningeal artery.Figure 1: Clinical photograph of the patient showing scalp swelling over the left temporoparietal region almost extending over the vertex: (a) front view and (b) side viewFigure 2: Post contrast CT scan brain showing contrast enhancing extra axial mass lesion over left high fronto parietal region and extending up to midline with enhancement of overlying scalp (a). Magnetic resonance imaging (MRI) of the brain axial T1 weighted section showing isointense lesion (b) and Axial T2 weighted section showing iso-hypointense lesion (c) over the left frontoparietal regionFigure 3: Magnetic resonance imaging (MRI) of the brain T2 coronal section showing large intracranial extra axial T2 iso-hypointense lesion over the left frontoparietal region (a) which was heterogeneously enhancing on contrast administration with few non enhancing are suggestive of necrosis (b)The patient underwent excision of the lesion under general anesthesia. Intraoperatively, the lesion showed involvement of the subcutaneous tissue, the galea, the pericranium, the frontal and the parietal bone, and a small portion of the dura. Left frontoparietal craniectomy was done, and the involved structures along with the dura were removed. The lesion was mildly vascular and partially suckable. Histopathological (HP) examination revealed a diffuse uniform monomorphic population of tumor cells of hematolymphoid origin with large neoplastic lymphocytes suggestive of diffuse large B-cell lymphoma (DLBCL) [Figure 4]. Immunohistochemistry (IHC) showed CD20 positivity suggestive of B-cell origin of the tumor and CD138 negativity.Figure 4: Photomicrograph showing a diffuse uniform monomorphic population of tumor cells of hematolymphoid origin with large neoplastic lymphocytesPostoperatively, his chest X-ray, abdomen/pelvis ultrasonography (USG), and bone marrow biopsy were normal. The patient received chemotherapy in the form of CHOP regimen (cyclophosphamide, doxorubicin (Adriamycin), vincristine (Oncovin), prednisolone) and local field radiation therapy. At 1.5 years’ follow-up, the patient was asymptomatic. Follow-up MRI revealed no evidence of residual or recurrent disease [Figure 5a–c].Figure 5: Follow up MRI of the brain showing complete resolution of the lesion on post contrast axial images (a), T2 weighted coronal images (b), and T1 weighted sagittal images (c)PLB is highly infrequent and was first mentioned by Oberling in 1928.[2] The criteria required for the lesion to be categorized as PLB are histopathological confirmation with no distant metastasis within 6 months of detection of the tumor and primarily single-bone involvement.[3] Our patient had all of the abovementioned diagnostic criteria. The cause of PLB is not fully understood yet; however, viral infection, immunodeficiency, organ transplantation, Paget’s disease of the bone, and inherited factors have been often recognized.[4] Our patient had none of these above factors. Calvarial lymphoma is usually seen in immunocompromised, old male patients with a mean age of 60.5 years.[5] The most common pathology seen with calvarial lymphoma is of DLBCL, ranging from 39% to 77%.[6-8] Primary dural lymphoma (PDL) is seen as a separate and distinct entity from calvarial lymphoma. It arise primarily from the dura matter. Histopathologically, it is lower-grade lymphoma, and B-cell variety is the most common.[6,9,10] Literature documents few reports of calvarial and intra-parenchymal invasion associated with PDL.[11-13] Calvarial lymphoma also needs to be differentiated from primary cutaneous lymphoma (PCL) of the scalp, which usually grows slowly and less frequently shows intracranial extension or extensive osteolytic lesions.[14] Due to the short duration of symptoms, widespread involvement of the left hemi-cranium with extra-, intra-, and cranial involvement along with HPE reports of DLBCL, we are of the opinion that the most likely diagnosis is calvarial lymphoma. The most common signs and symptoms of calvarial lymphomas are painless scalp swelling (90%), headache (30%), and focal neurologic deficit (20%) depending on the location of the swelling or convulsions (10%). Rarely, they may present with proptosis.[5] However, these symptoms and signs are nonspecific; thus, further radiological and histological studies are needed for a conclusive diagnosis. CT displays a characteristic feature of a permeative growth pattern or a moth-eaten pattern, a large soft tissue component, and very little cortical obliteration.[15] However, this mimics the appearance of other diseases such as Langerhans cell histiocytosis, osteomyelitis, leukemia, plasmacytoma, Ewing sarcoma, osteomyelitis, and metastatic cancer. Early in the course of calvarial lymphoma, minimal bony change is seen; gradually, it destroys the bone completely. The tumor grows rapidly and invades the dura and brain; thus, early diagnosis plays a crucial role.[16] The MRI signal intensities are nonspecific, and these tumors are iso to hypointense on T1-weighted images and iso to hyperintense on T2-weighted images with homogenous contrast enhancement.[1] Primary malignant calvarial lymphoma is also commonly mistaken as a meningioma. The standard treatment for calvarial lymphoma has not yet been established; however, surgical removal followed by chemotherapy and radiation therapy are the basic treatment modalities. Surgery followed by local radiation is the favored treatment for a single lesion of extra-nodal disease, but if the lesion is entirely removed, follow-up with imaging without further treatment can be considered. In terms of chemotherapy, CHOP regimen is often used. High-dose methotrexate might also be effective. About 40%–60% of the patients show survival for 5 years.[1] However, if it involves the brain parenchyma, the median survival drops down to 10.5 months from 17.5 months.[4] Abad Cherif El Asri et al.[6] reported 39 cases, where the average age of the patient was 60 years, with no gender predominance. The predominant complaint in these patients was scalp swelling. Out of 39 patients, 21 patients underwent only biopsy, 17 patients underwent excision, and in one patient, diagnosis was made at autopsy. Nineteen patients were diagnosed to have DLBCL. Out of 17 patients who underwent surgical excision, four underwent only total or gross total excision, another four were subjected to radiotherapy post excision, and nine patients were subjected to radiotherapy and chemotherapy post-surgery. Amongst the 22 cases for which the outcome was available, 16 patients had a follow-up of up to 1 year, 13 patients were alive after 1 year, and three patients had succumbed. Tatsuya Uchida et al.[17] encountered a patient who presented with scalp swelling, which they excised totally. Chemotherapy was administered postoperatively, and radiotherapy was planned. Tashiro et al.[18] also reported two cases of DLBCL of the cranial vault. Both patients underwent gross total excision of the tumor. Both had received chemotherapy according to standard protocols. One of them had developed local recurrence postoperatively for which radiotherapy was administered. Due to the paucity in the number of cases reported, often primary calvarial lymphoma may not be considered as a differential diagnosis of scalp swelling. However, as this lesion shows drastic growth and invasion to the surrounding structures, including the brain parenchyma, it should be picked up early and active treatment is of utmost importance. Although the outcome in the literature is variable, surgery followed by radiation, and chemotherapy help patients with a favorable outcome. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.