Etiology
- Monoclonal or polyclonal proliferations of plasma cell or plasmacytoid lymphocytes
- IgG is most common, followed by IgA.
- 4 main variants (Burkat, Surv Ophthalmol. 2009)
- Polyclonal plasma cell tumor
- Heterogenous population of plasma cells and lymphocytes
- Typically affect conjunctiva, but can be found in the orbit
- Solitary pPlasmacytoma
- Isolated monoclonal plasma cells within bone
- No other skeletal bone involvement
- Extramedullary plasmacytoma
- Develops in soft tissue
- Commonly occur in upper respiratory tract and sinuses with orbital extension
- Plasma cell myeloma (multiple myeloma)
- Arise from bone marrow of skeletal bone; leukemic stage
- Lytic lesions of bone
- Necrobiotic xanthogranuloma (NXG)
- Histiocytic nodules that affect eyelids and periorbitum
Epidemiology
Solitary Plasmacytoma
- 6th–7th decades
- Male to female: 3:1
Extramedullary plasmacytoma
- 7th–8th decades
- Male to female: 2:1
Plasma cell myeloma
History
- Typically a manifestation of systemic disease; rarely a solitary focus in the orbit
- 65% of patients presenting with orbital involvement are carrying a diagnosis of multiple myeloma (MM) (Burkat, Surv Ophthalmol. 2009).
- Weight loss/fatigue
- Bone pain
- Particularly in multiple myeloma, whereas solitary plasmacytoma typically do not cause pain
- Anemia
- Hypercalcemia
- Lytic lesions of bone
- Peripheral neuropathy
- Cutaneous rash
Clinical features
(Burkat, Surv Ophthalmol. 2009)
- Slowly progressive proptosis (axial or abaxial) is the most common presenting sign.
- Periorbital swelling (Figure 1)
- Loss of vision
- Ptosis
- Diplopia
- Can be bilateral, however unilateral is more common (Malik, Indian J Ophthalmol. 2009)
- Location varies:
- Most commonly superotemporal, posterior, and extraconal
- Bone involvement is common.
- Solitary plasmayctoma
- Multiple myeloma
- Can also affect the lacrimal gland, optic nerve and extraocular muscles
- Amyloidosis develops in 8%–15% of patients.
- Should also be included in the differential diagnosis for a multiple myeloma patient with an orbital or subconjunctival mass
- Although the orbit is the most common location, conjunctival and anterior segment lesions have also been documented.
- Systemic myeloma can present with orbital muscle swelling and proptosis due to paraproteinemia (Rootman, Diseases of the Orbit: A multidisciplinary approach 2002).
Figure 1. Top: Periorbital swelling seen clinically. Bottom: Axial CT of the patient demonstrating periorbital and intracranial involvement with bony remodeling.
Testing
- Patients need to be evaluated for MM.
- Serum/urine protein electrophoresis for immunoglobulin components
- Light chain (Bence-Jones protein)
- Heavy chain (IgG, IgA, etc.)
- 15% of cases do not have immunoglobulinemia (Bataille, New Engl J Med 1997).
- Free light chain assay
- Serum calcium elevated in MM
- Erythrocyte sedimentation rate
- Alkaline phosphatase level elevated in MM
- Complete blood count with differential
- Bone marrow aspirate
- Skeletal bone imagery
- Scintigraphy of the head and neck
- Positron emission tomography (PET) scan
- Computed tomography
- Solitary plasmacytoma of bone: bone erosion
- Extramedullary plasmacytoma: homogeneous, nonencapsulated mass with mild enhancement; molds to surface of globe
- Plasma cell myeloma: soft tissue mass in retrobulbar space; may see lysis of walls of orbit; appears attached to underlying bone
- Magnetic resonance imaging (Jackson, Br J Radiol. 1993) (Figure 2)
- T1: Intensity similar to extraocular muscles
- T2: Intensity similar to orbital fat
- Useful in distinguishing from metastasis which generally are more intense that fat
- Tissue diagnosis critical in diagnosing the lesion and subsequent evaluation
Figure 2. MRI and CT of a patient with plasmacytoma involving brain and R lateral orbit. Note the relative paucity of bony changes on the CT and the variable densities of the mass on T1- and T2-weighted images.