Plasmacytoma of the clivus.

We report a case of solitary plasmacytoma of the clivus in a 55 year old male.

Introduction

Plasmacytoma is a localized clonal proliferation of plasma cells arising in bone or soft tissue. It accounts for < 1% of head and neck tumors. Plasmacytoma is classified by World Health Organization into solitary bone plasmacytoma (SBP) and extramedullary plasmacytoma (EMP).[1] The most common site is upper aerodigestive tract, 80% occurring in nasal cavity and nasopharynx. Solitary intracranial plasmacytoma is rare, with only close to 20 cases reported in the literature.[2] Most of the cases reported show involvement of the skull vault. Involvement of the base of the skull is rare with only a few exceptional reports citing clivus as the site.[3] We report a case of plasmacytoma of the clivus in a 55 years old male.

Case Report

A 55-year-old male presented with insidious onset diplopia while looking to the right and to distant objects of 3 months duration. There was no history of visual blurring, jaw deviation, facial asymmetry, hearing loss or tinnitus. There was no associated headache, vomiting, seizures or loss of consciousness, limb weakness, gait, and bowel or bladder disturbances. On examination, patient was conscious with stable vital signs. Higher mental functions were normal. There was right side sixth nerve palsy and nystagmus on looking to the right. Visual acuity and visual field examination were normal. There were no other cranial nerve, motor or sensory deficits. Other system examinations were within normal limits. Magnetic resonance imaging of the brain showed an expansile mass lesion involving entire clivus that was T1- and T2-isointense and showed contrast enhancement. There was erosion of posterior wall of the sphenoid sinus with lesion bulging into the sinus. Pituitary was normal [Figure 1]. With a preoperative diagnosis of clival chordoma infiltrating into the sphenoid sinus, the lesion was decompressed by subfrontal trans basal approach.

Figure 1

(a) Magnetic resonance imaging brain shows an expansile lesion involving entire clivus and eroding the posterior wall of sphenoid sinus. (b) Saggital view of the lesion

Microscopy showed respiratory epithelium with an underlying neoplasm composed of sheets of plasma cells with a moderate amount of cytoplasm and eccentric round nuclei [Figure 2]. Cells were positive for CD 138, CD 38 and CD 56, while negative for CD 20, cytokeratin and synaptophysin. Ki 67 (MIB) labeling index was < 5%. Cells were kappa light chain positive and negative for lambda light chains thus establishing monoclonality. A diagnosis of plasmacytoma of clivus was given, and workup for myeloma was suggested.

Figure 2

(a) Microscopy shows a neoplasm with overlying respiratory epithelium ×40, (b) sheets of plasma cells ×400 and (c) high power view of plasma cells ×1000. (a-c: H and E) with moderate amount of cytoplasm and eccentric round nuclei

Patient underwent whole-body X-ray studies, serum and urine electrophoresis, complete blood counts, serum calcium levels and a bone marrow biopsy, as part of myeloma investigations, which were negative.

Patient received radiotherapy (50 gray given in 25 fractions) and is now 8 months postoperative and doing well. The right side lateral rectus palsy is still persisting.

Discussion

Plasma cell tumors affecting the skull base generally appear as a manifestation of underlying multiple myeloma (MM). Solitary plasmacytoma of the skull base is rare with < 10 reported cases of clival plasmacytoma in literature.[2345] A brief summary of the cases is provided in Table 1. Clival plasmacytoma may represent an SBP or may be involved by EMP involving the submucosa of the sphenoid sinus as in our case.

Table 1

Summary of the reported cases of clival plasmacytoma including the present case

By definition, patients with solitary plasmacytoma do not have evidence of underlying systemic disease at the time of diagnosis.[1]

In general, solitary intracranial plasmacytomas remain asymptomatic for a long period of time. The symptoms are related to compression of cranial nerves and headaches. Tumors in the clivus produce diplopia due to compression of the sixth cranial nerve, which has the longest path in this anatomic region. This was true in our case also.[2]

Other cranial nerves affected include II, V, VII and VIII, according to the order of frequency. Rare case reports of compression of the posterior inferior cerebellar artery leading to a lateral medullary and bulbar syndrome are also on record.[5]

A radiological differential of a lesion in clivus includes chordoma, chondrosarcoma, meningioma, invasive pituitary adenoma, lymphoma, metastasis, and osteosarcoma. Positron emission tomography with fluorodeoxyglucose has been found to aid in the detection of unsuspected sites of medullary and extramedullary disease.[5]

Due to the rarity of plasmacytoma at the skull base and the nonspecific clinical and radiological findings, in most cases the diagnosis is obtained through histopathology, as in our patient also.

Histologically, plasmacytomas are characterized by a diffuse or sheet-like proliferation of plasma cells with varying degrees of maturity and atypia. The nuclei are oval to round and eccentrically located with a dispersed (“clock-face”) nuclear chromatin pattern and a clear or halo area. Neoplastic nature of plasma cells is established by proving the monoclonality.

This case is presented to highlight that though rare, plasmacytoma should be considered in the differential diagnosis of skull base lesions associated with early involvement of cranial nerves. All solitary plasmacytomas patients should be evaluated to rule out underlying MM and thoroughly followed up for any signs of evolution to MM.

Average survival of patients with MM is 3 years, whereas patients with a solitary lesion have a better prognosis. EMP progressing to MM is <30% with a 10-year disease-free period of 70%. In SBP, however the likelihood of progression to MM is >50% with a 10-year disease-free period of only 16%.[367]