Abstract
Extramedullary plasmacytomas are localized plasma cell neoplasms which arise within the soft tissues, by definition they cannot arise within bone. The most common location for extramedullary plasmacytoma is the nasopharynx and paranasal sinus. According to Wax et al, 75% of extramedullary plasmacytomas occur in sinonasal/nasopharyngeal area, 12% in the oropharynx, 8% in the larynx, other sites in the head and neck that have been reported include tongue, minor salivary glands, thyroid, parotid, orbit, temporal bone.1 Kidney is a rare site for plasmacytoma. The aetiology of the extramedullary plasmacytoma is unknown. We present a case of primary renal plasmacytoma which is a clinical rarity. Diagnosis was confirmed only on histopathology of the specimen after ruling out other sites of myeloma. Patient was treated with radical nephrectomy followed by radiotherapy and chemotherapy. The case is presented due to its rarity.

Introduction
Plasmacytoma, a localized extramedullary
mass of plasma cells, is one manifestation of multiple myeloma. Extramedullary plasmacytoma is a rare malignant neoplasm typically arising outside the bone marrow of patients who show no clinical evidence of multiple myeloma. The most common location for extramedullary plasmacytoma is the nasopharynx and paranasal sinus, representing nearly 4% of all nonepithelial tumours of the nasal cavity, nasopharynx, and paranasal sinuses.2 Primary renal plasmacytomas are rare lesions. We present a case of Primary renal plasmacytoma whose diagnosis was confirmed only on histopathology report of the specimen. Hence this clinical entity though rare has to be kept in mind in cases of renal malignancy.

Case Report
We present a case of 60 year old male who was referred by a physician for ultrasonograhic findings of left renal mass. Patient had history of weight loss with occasional low grade fever since 3 months. Clinical examination revealed a ballotable enlarged left kidney. Patient was investigated further. CT scan revealed a mass lesion involving the entire left kidney with a small lymph node in the aortocaval region. Hence CT scan was suggestive of Left renal malignancy. Left kidney showed poor functioning while right kidney had good function. Patient was worked up for surgery. Intra-operative findings revealed left renal mass with a lymph node at the hilum. Left radical nephrectomy was done. Post-operatively patient had increased lymphorrhoea through the drain. Initially for first ten days it was 600-800 ml/day and later on decreased. Drain was removed on 20th post-operative day when drain output was negligible. Histopathology of the specimen showed Plasmacytoma of the left kidney i.e. tumour tissue with plasmacytoid cell infiltration (Fig. 1). Lymph node showed reactive hyperplasia.

In view of histopathology report, patient was investigated for other sites of myeloma. Urine Bence Jones proteins were negative, serum electrophoresis showed no M-band and Bone marrow biopsy was normal. This all proved it to be primary renal plasmacytoma which is a rarity. Patient was given radiotherapy and chemotherapy post-operatively for the same. Follow-up of three months has shown him to be symptom and disease free.

Fig. 1 : Histopathology slide showing plasmacytoma with atypical plasma cell infiltrate (40X).

Discussion
Extramedullary plasmacytoma is a rare malignant neoplasm typically arising outside the bone marrow of patients who show no clinical evidence of multiple myeloma. The most common location for extramedullary plasmacytoma is the nasopharynx and paranasal sinus. According to Wax et al, 75% of extramedullary plasmacytomas occurred in sinonasal/nasopharyngeal area, 12% in the oropharynx and 8% in the larynx.1 Extramedullary plasmacytoma has been reported in the pleura, mediastinum, spermatic cord, ovary, intestines, pancreas, breast, and skin. Extramedullary plasmacytoma arising in the kidney is uncommon. Extramedullary plasmacytoma affects men 3-4 times more often than in women and typically occurs in the 6th to 7th decade with over 95% of cases occurring in patients above 40 years of age.¹

The aetiology of the extramedullary plasmacytoma is unknown. Proposed risk factors include chronic antigenic stimulation such as osteomyelitis, cholecystitis, rheumatoid arthritis, bacterial flora. Clinically, the tumour mimics a renal cell carcinoma or a transitional cell carcinoma of the renal pelvis. Our patient was a 60 year old male who presented with renal lump and mimicked the presentation of renal carcinoma.

Histopathologic examination can not distinguish multiple myeloma from an extramedullary plasmacytoma, further evaluation is necessary to exclude the presence of systemic disease and confirm the diagnosis of primary renal plasmacytoma. Abemayor, et al in review of plasma cell disorders have recommended a complete blood count with white blood cell count and platelet count, bone marrow biopsy, serum biochemistry including calcium, blood urea nitrogen, creatinine, uric acid, serum protein, serum and urine electophoresis, and a skeletal survey to rule out multiple myeloma.³

Normal bone marrow examination, absence of lytic bone lesions on skeletal series, and low paraprotein levels are necessary to establish the diagnosis of extramedullary plasmacytoma. High levels of paraprotein in the serum or urine should raise the clinician's suspicion of a disseminated process, since paraprotein levels correlate directly with tumour burden.³ In our case histopathology report revealed renal Plasmacytoma. Hence bone marrow biopsy, urinary Bence Jones Proteins and Serum protein electrophoresis were done which ruled out systemic disease and confirmed the diagnosis of primary renal plasmacytoma.

After a diagnosis is confirmed, extramedullary plasmacytoma can be staged as follows: Stage I is localized and controllable disease, Stage II is local extension or involvement of the lymph nodes, and stage III is disseminated disease.

According to Batsakis,4 the natural history of extramedullary plasmacytoma may be characterized in the following five ways:

• localized, solitary controlled by surgery, radiotherapy, or both, does not recur or become disseminated
  
• locally recurrent controlled by additional therapy
• aggressive, persistent, or recurrent disease, producing death through uncontrollable local extensions
• local disease with "metastatic" involvement of regional lymph nodes without evidence of distant spread
• local disease, recurrent or otherwise followed by dissemination and development of multiple plasma cell neoplasms and/or multiple myeloma

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2. Fu YS, Perzin KH. Nonepithelial tumors of the nasal cavity, paransal sinuses and nasopharynx. Cancer 1978; 42 : 2399-406.
3. Abemayor E, Canalis RF, Greenberg P, et al. Plasma cell tumors of the head and neck. J Otolaryngology 1988; 17 : 376-81.
4. Batsakis JG, Fries GT, Goldman RT, Karlseberg RC. Upper respiratory tract plasmacytoma. Arch Otolaryngol 1964; 79 : 613-8.
5. Wiltshaw E. The natural history of extramedullary plasmacytoma and its relation to solitary myeloma of bone and myelomatosis. Medicine 1976; 55 : 217-38.