Track: Case Reports

Abstract:

INTRODUCTION

Primary cutaneous plasmablastic lymphoma (PCPL) are rare and usually arise in the setting of immune deficiency or dysregulation. We present a case of an immunocompetent patient with incidental PCPL and subsequently incidental systemic mastocytosis upon staging.

CASE DESCRIPTION

The case was a 62-year-old systemically well man who had an excision for basal cell carcinoma in the antecubital fossa. There was an incidental 2 mm foci of atypical lymphoid infiltrate within the subcutis composed of large cells with prominent nucleoli, coarse chromatin and scant amphophilic cytoplasm in a background of lymphoplasmacytic infiltrate.

The atypical cells were positive for CD79a (<5%), CD138 (50%), MUM1, CD30 (30%), +C-MYC (60% to 70%) and kappa light chain. Ki-67 proliferative rate of >90%, and negative for EBER, CD20, BCL2, CD56, PAX5, ALK, p53 (wild type), BCL6, CD10 and TdT. The background mature plasma cells were polyclonal. MYD88 mutation was not detected.

Routine bloods, IgG, IgA and IgM were normal. ANA and serology for HIV, syphilis, HBV and HCV were negative. SPEP did not show M protein. PET CT did not show FDG avid nodal or definite extranodal disease. There was diffuse FDG uptake within the bone marrow of axial appendicular skeleton. Bone marrow was mildly cellular with paratrabecular aggregates of >15 mast cells. There was no lymphoma involvement. Qualitative c-kit D816V mutation and serum tryptase >200 confirmed systemic mastocytosis. He was staged as 1AE EBV negative plasmablastic lymphoma that was excised. The patient was followed up closely with no further treatment. There was no recurrence at 7 months follow up.

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Stephen Lade