Extramedullary plasmacytoma: an unusual neoplasm in a HIV-positive patient

Introduction

The advent of effective antiretroviral medications has contributed to the rising trend of non-AIDS-defining illnesses like certain cancers. The risk of plasma cell disorders is higher in the HIV-infected population and ranges from polyclonal hypergammaglobulinemia to aggressive multiple myeloma. ¹ Extramedullary plasmacytomas (EMPs) are rare solitary tumours that originate from non-bony soft tissues like the upper respiratory tract. ² EMPs constitute less than 5% of plasma cell neoplasms, ³ of which 15% usually progress to multiple myeloma. ² EMPs, unlike plasmablastic lymphomas, are not common in HIV infection. ³ We report a rare case of solitary EMP with unusual features in a patient affected with HIV.

Case report

A 44-year-old man presented with a swelling on the right side of his face, of 20 days duration. He was a known to be HIV-positive and had been taking antiretroviral therapy (ART) for the past two years. The swelling, which was initially indolent, had rapidly increased in size over the previous 10 days, and was associated with pain and blockage of the right side of the nose. He was treated with antibiotics elsewhere with no improvement. There were no other local or systemic symptoms.

On examination, there were dull erythematous tumid plaques of sizes 1 cm × 1 cm to 1.5 cm × 2 cm coalescing to form nodules of firm-to-hard consistency on the right side of the nose and extending onto the infraorbital part of the right eye. There was superficial ulceration near the superomedial aspect of the nose. There were dilated veins on the forehead. There were no regional lymph nodes. ENT examination revealed a bulge in the lateral wall of the right nasal cavity with normal mucosa.

Histopathology of the lesional skin showed a tumour in the dermis and the subcutaneous tissue composed of sheets, nests and loose clusters of small- to medium-sized round plasmacytoid cells with eosinophilic cytoplasm and mild nuclear pleomorphism, admixed with many mature plasma cells (Figure 1) and few plasmablasts (Figure 2). Epidermis was spared. Tissue cultures were negative for bacteria, mycobacteria and fungi. On immunohistochemistry, the tumour cells were diffusely positive for CD138 (Figure 3) and MUM1 (Figure 4). MIB 1 index was 60% (Figure 5). CD3, CD20, CD99, MPO, cytokeratin and synaptophysin were negative. CD56 and cyclin D-1 were negative, which ruled out extramedullary multiple myeloma. EBV LMP-1 was negative. OPEN IN VIEWER

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Figure 2.

Photomicrograph showing few plasmablasts. (black arrow) (H&E stain, 400 × ).

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Figure 3.

Photomicrograph showing CD 138 showing membrane positivity.

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Figure 4.

Photomicrograph showing MUM1 positivity of the tumour cells.

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Figure 5.

Photomicrograph of the tumour cells showing a high MIB1 (60%).

Magnetic resonance imaging (MRI) revealed an underlying osteolytic lesion of the ethmoid and the medial orbit wall. Radiological evaluation of the rest of the bones revealed no involvement.

Bone marrow histopathology revealed only 8% of plasma cells.

Additional laboratory tests showed the presence of 1 g% of a monoclonal protein in serum electrophoresis. On immunofixation, it was found to be of IgG kappa type and the other immunoglobulin levels were normal. Calcium levels and renal parameters were normal. His CD4 + T-cell count was 108 cells/µL.

In view of his localised solitary plasmacytoma, he was recommended for low-dose radiation along with continuation of the ART; however, he was lost to follow-up.

Discussion

Neoplasia of plasma cells acquires special clinical characteristics in patients living with HIV, especially in men with low CD4 counts. ⁴ The chronic antigen stimulation and immunodeficiency are considered to be the driving forces for this process. ⁴ In addition, plasmablastic lymphoma, a more common tumour in HIV-infected people, was ruled out by the mature morphological appearance of the tumour cells on histopathology, EBV negativity and a strong positivity for CD 138 and MUM1.

The unique features in our patient were skin involvement, which is a very rare site for the EMP; the common sites being the paranasal sinuses and aerodigestive tract. ⁵ There was a high proliferation index; the MIB1 index was 60%, denoting its local aggressiveness. There was solitary localised osteolytic involvement in the absence of bone marrow involvement, which is a very rare occurrence. ⁶ Finally, the presence of a monoclonal component of IgG kappa type, probably indicating the secretory nature of the tumour, which is seen in less than 25% of patients with EMP ⁵ , was also seen in our patient.

Though EMP is considered to have a good prognosis, ⁷ in the context of HIV it may even be the initial presentation of multiple myeloma. ⁴ In view of the high proliferative rate of tumour, close monitoring of clinical and biochemical parameters is required to detect early progression to multiple myeloma.

Conclusion

Differentiating between plasmablastic lymphoma, plasma cell myeloma and the solitary EMPs is in itself a diagnostic challenge. This practical difficulty in clinical diagnosis is exaggerated in the presence of HIV due to its unusual features, making the role of pathologists crucial and the role of extensive workup mandatory. We report this case for its rarity, histopathological dilemma and its atypical features in HIV infection.