A 72‐year‐old female with an intraventricular mass

CLINICAL HISTORY

A 72‐year‐old woman presented with progressively hearing loss over past 10 years and recently developed pain in her left ear and face. The patient had a history of migraine for most of her adult life. On physical examination, facial muscle and sensation were symmetric and hearing was intact to finger rub bilaterally. Subsequent MRI revealed an enhancing mass measuring 2.6 × 1.6 × 2.1 cm³ within the left lateral ventricular atrium (Figure 1A), compatible with intraventricular meningioma. There was increased perfusion and blood volume within the mass and surrounding confluent T2 hyperintensities suggestive of vasogenic edema (Figure 1B). She underwent a craniotomy and tumor excision. During surgery, it was noted that the tumor was rising off the choroid plexus. A biopsy of the mass was submitted for intra‐operative consultation. Following examination of the smear and frozen section, a debulking procedure was undertaken.

Figure 1.

MICROSCOPIC PATHOLOGY

Intraoperative evaluation showed a dense, diffuse infiltrate of small lymphocytes (Figure 1C), which was later confirmed on paraffin sections of the subtotal resected specimen, with frequent plasmacytoid lymphocytes and scattered plasma cells more readily observed (Figure 1D). There was minimal mitotic activity and no evidence of necrosis. Immunohistochemistry showed a predominance of CD20 positive B cells (Figure 1E) with admixed CD3 positive T cells (Figure 1F). CD138 highlighted numerous plasma cells and plasmacytoid lymphocytes (Figure 1G). Immunostains for lambda and kappa light chains showed a restricted kappa light chain. Majority of the plasmacytoid cells were positive for IgM and IgG, only a few were immunoreactive for IgA. An in situ hybridization for EBV (EBER) was negative. What is your diagnosis?

DIAGNOSIS

Primary CNS lymphoplasmacytic lymphoma

DISCUSSION

Other than diffuse large B‐cell lymphoma, lymphomas manifesting primarily in the CNS are rare 3. They include low‐grade B‐cell and T‐cell lymphomas (3% of all CNS lymphomas), the majority are of B‐cell lineage 2. Primary CNS low‐grade B‐cell lymphomas almost exclusively affect adults. Patients presents with seizures, visual defects, focal neurological findings and/or memory impairment 2, 3. There is no association with immunodeficiency except in rare cases of extranodal marginal zone lymphoma (MALT) 4. As one subgroup of low‐grade B‐cell lymphomas, primary CNS lymphoplasmacytic lymphomas (LPL) are even rarer. So far in the literature only 22 cases have been reported 1. Therefore, it is critical to confirm a neoplastic process, not a chronic inflammatory process. Meticulous staging to exclude a systemic lymphoma is also essential.

In terms of differential diagnoses, intraventricular tumors are rare lesions that make up 0.8%–1.6% of all intracranial tumors. They are however more common in children and comprise around 16% of childhood and adolescent intracranial tumors. These are a histologically heterogeneous group of tumors that can be divided into primary and secondary intraventricular tumors. “Primary tumors” are neoplasms that originate from the ependymal or subependymal lining (ependymoma, subependymoma and subependymal giant cell astrocytoma), septum pellucidum (central neurocytoma), choroid plexus (choroid plexus papilloma and carcinoma), and the supporting arachnoid tissue (meningioma). “Secondary or paraventricular tumors” is a term used when these neoplasms originate from adjacent brain substance and demonstrate more than two‐thirds exophytic growth within the ventricle. Although the neuroimaging diagnosis may be challenging, it is in general not difficult to differentiate intraventricular lymphoma from other intraventricular neoplasms based on histologic examination. If there is any doubt, a lack of immunoreactivity to EMA, cytokeratin, GFAP, or synaptophysin will help distinguish the lymphoma apart.

Perhaps more diagnostically challenging, is to separate LPL from other low‐grade B‐cell lymphoma, including small lymphocytic lymphoma, MALT lymphoma and follicular lymphoma. By definition, LPL does not fulfill the criteria for any of the other small B‐cell lymphoid neoplasms that may have plasmacytic differentiation. Because the distinction between LPL and these other lymphomas, especially MALT lymphoma, is not always clear‐cut, some cases may need to be diagnosed as a small B‐cell lymphoma with plasmacytic differentiation and a differential diagnosis provided.

In general, the behavior of LPL is indolent and patients usually do well 1, 3. There are no set guidelines for treatment. Treatment has varied widely and has included complete or partial resection, steroids, radiation, chemotherapy, and combinations of these despite there is little evidence that adjuvant chemo or radiation would increase the chance of cure. Treatment is aimed at control of the disease process and prevention of end organ damage. There is no known benefit to early treatment when patients are asymptomatic or without organ impairment.