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A 58-year-old woman with previously asymptomatic multiple myeloma presented acutely to the emergency medical intake with a severe frontal and left-sided headache. On examination she was apyrexial and normotensive and the rest of the general and, in particular, the neurological examination was normal. Investigations at that time revealed a haemoglobin of 8.8 g/dl, white cell count of 5.01 × 109/l, erythrocyte sedimentation rate of 138 mm/h and plasma viscosity of 3.6 centipoise (1.5–1.72). Serum electrophoresis revealed a paraprotein level of 25 g/l (IgAκ), a κ:λ ratio of 16.2 (1–2.7) and a β2-microglobulin of 2.2 mg/l (1.2–2.4). Bone marrow aspirate demonstrated 18% plasma cells (normal < 5%).Twelve hours post admission she developed neurological symptoms and orbital pain. An urgent computed tomography (CT) scan of the orbits and paranasal sinuses was performed (figure). The lesion demonstrated on the CT was removed surgically.
- What is the probable diagnosis and differential diagnosis?
- Where are these tumours most commonly found?
- Given the site of the lesion, what neurological signs might have accompanied her deterioration?
- What would be the treatment of choice for a solitary tumour such as this?
The diagnosis is a left retro-orbital plasmacytoma. Differential diagnosis is shown in box FB1.
A plasmacytoma is a not uncommon complication of multiple myeloma. It may rarely manifest as a primary tumour, occurring without evidence of other disease. In our patient histology of the removed mass demonstrated mitotic figures in a plasmacytoid tumour cell infiltrate. Immunostaining demonstrated positivity for IgG, IgA, and κ-light chain consistent with myeloma, suggesting spread of pre-existing disease.
Extramedullary plasmacytomas (EMP) may involve any extramedullary organ or tissue but most are found in the head and neck region, usually in the mucosa of the oronasopharynx or paranasal sinuses.1It is, however, rare for this solitary tumour to involve the orbit.2 EMPs account for approximately 3% of all paranasal sinus and nasal cavity tumours.3 Localised pain and epistaxis are the two most common presentations with proptosis and sixth nerve palsy being much rarer.4
The rapid progression of the neurological symptoms was related to the mass effect of the tumour, possibly secondary to haemorrhage into the lesion. As the lesion was located at the apex of the orbit this led to:
diplopia secondary to a left sixth and partial third nerve palsy
a left relative afferent pupillary defect
rapid deterioration in vision in the left eye.
EMPs are highly radiosensitive and radiotherapy is potentially curative for a primary EMP. Surgery is reserved as a second-line treatment according to the tumour's response to radiotherapy.5 However, in patients with pre-existing multiple myeloma, radiotherapy and surgery are used more often as palliative procedures, in addition to the treatment of the underlying condition.
Left retro-orbital plasmacytoma.