Discussion:
Plasmacytomas are immunoproliferative, monoclonal tumors of the β-cell line and are classified as non-Hodgkin‘s lymphoma. Extramedullary plasmacytomas present as a localized mass lesion. About 75% of them occur in the upper respiratory tract and also they may occur in a variety of anatomic sites [2,4]. The differential diagnoses of extramedullary plasmacytoma include reactive lesions with an abundance of plasma cells, lymphomas with marked plasma cell differentiation. Distinction from lymphoma with extreme plasma cell differentiation may be problematic[5]. Lymphoplasmacytic lymphoma, immunoblastic or plasmablastic large cell lymphomas, and especially MALT may be misdiagnosed as plasmacytoma[6,5]. Moreover, the distinction of extramedullary plasmacytoma from both solitary plasmacytoma of the bone and multiple myeloma is sometimes very difficult.
Mayoclinic diagnostic criteria for solitary plasmacytoma include 1) biopsy-proven solitary lesion of bone or soft tissue with evidence of clonal plasma cell,2) normal bone marrow with no evidence of clonal plasma cells, 3) normal skeletal survey,4) absence of end-organ damage such as anemia, hypercalcemia, renal failure or additional lytic bone lesions,5) low or absent serum or urinary level of monoclonal immunoglobulins[5].
In the present case, a systemic workup for finding dissemination of tumor cells including bone marrow aspiration, skeletal radiographic survey, complete blood count, serum biochemistry analysis, and monoclonal immunoglobulin levels of serum and urine did not reveal evidence of spread and the sphenoid sinus was the sole site of tumor. Therefore, extramedullary plasmacytoma of the sphenoid sinus was confirmed in this clinical case.
Based on the literature review, extramedullary plasmacytomas limited to the sphenoid sinus are extremely rare. It was estimated that only 1.6 % of extramedullary plasmacytomas arise from the sphenoid sinus that concluded approximately 15 cases until 2013. Moreover, in the localized sphenoid sinus tumor, the symptoms are usually non specific. when the tumor extended, visual loss, diplopia and, facial pain can be presented. [7, 8] Humphrey et al [9] reported an extramedullary plasmacytoma of the sphenoid sinus that presented with isolated VIth-nerve paralysis. In our presented case progressive ocular muscle paralysis and ptosis were the clinical manifestations. Orbital space-occupying lesions presenting with painful ophthalmoplegia are mostly due to malignancies that may originate from inside or outside of the globe [10]. In our case, the sphenoid originated tumor extended to the right orbital globe. Ampil et al [11] reported cavernous sinus involvement by extramedullary plasmacytoma of the sphenoid sinus which presented with retro-orbital headache. CT-angiography in our case showed cavernous sinus involvement and the patient‘s first complaint was headache 3 months earlier to admission.
The typical treatment for extramedullary plasmacytoma is local radiation, usually with radiotherapy in the range of 40 to 50 Gy[12]. Galieni et al [12] suggested that surgical removal of solitary extramedullary plasmacytoma could be performed for small masses and as secondary therapy after failure of local irradiation in the elimination of mass. Miller et al [13] reported a case of sphenoid sinus plasmacytoma that was treated with radiation 6400 cGy. Chemotherapy has not been successful in extramedullary plasmacytoma treatment but Wein et al [14] treated a patient with sphenoclival plasmacytoma with systemic chemotherapy. Surgical resection of tumor by endonasal transsphenoidal approach with complementary radiotherapy was performed for our patient. After 6 months of follow-up, there have been some improvements in the clinical symptoms of the patient. Although, paresis of ocular muscles is somewhat resolved, decreased visual acuity still exists. Hardwood et al [15] reported two cases of radiotherapy failure in the treatment of solitary extramedullary plasmacytoma which one of them was in the sphenoid sinus. With this in mind, 10-year disease-free survival rates are reported to be 70-80% [5], further follow-up with greater care is required for our patient.