Primary mediastinal large B-cell lymphoma (PMLBL) is an uncommon non-Hodgkin lymphoma with a distinct clinicopathological entity in the WHO classification of lymphoid malignancies. It is known to originate from B-cells of the thymus. It mimics thymic neoplasms and other lymphomas clinically and histopathologically. We reported a 33-year-old obese man who presented with shortness of breath off and on for 4 years. Radiologically, there was a huge anterior mediastinal mass. Tru-cut biopsy was initially diagnosed as type-A thymoma. Histopathological examination of the excised specimen revealed PMLBL with stromal fibrosis and sclerosis which created a diagnostic difficulty. The neoplastic cells varied from medium-sized to large pleomorphic cells, including mononuclear cells with centroblastic and immunoblastic features as well as bi-lobed Reed Sternberg (RS)-like cells and horse-shoe like hallmark cells. Some interlacing spindle cells and epithelioid cells were also present. Immunohistochemically, tumour cells expressed diffuse positivity for LCA, CD20, CD79a, CD23, Bcl2, MUM-1 and heterogenous positivity for CD30 and EMA, and were negative for CD10, CD15 and ALK. Ki67 scoring was very high. Tumour cells infiltrated into peri-thymic fat and pericardium. No malignant cells were detected in the pleural fluid and there was no bone marrow infiltration. The patient showed partial response to 6 cycles of RICE chemotherapy, and was planned for second line chemotherapy using hyper-CVAD regimen followed by autologous stem cell transplantation. This case illustrates the importance of thorough sampling and immunohistochemistry in differentiating PMLBL from its differential diagnoses.

Nasopharyngeal carcinoma is a commonly encountered malignancy in endemic regions of the world namely South East Asia, China and Hong Kong. In Malaysia, the ethnic Chinese population is particularly at risk due to genetic susceptibilities and environmental exposure to carcinogenic agents. We herein report a case of nasopharyngeal carcinoma in a middle-aged man of Malay ethnicity who presented with nasal blockage and neck nodes. The biopsy of the nasopharyngeal mass came back as papillary variant of nasopharyngeal carcinoma. The commonly reported histopathological types are the keratinizing and non-keratinizing types, and rarely the basaloid type. In this case report, we aim to highlight one of the rare variants of the non-keratinizing nasopharyngeal carcinoma. When diagnosing the non-keratinizing type, appreciation of the different morphological variants is crucial not only to help aid in procuring an acurrate histopathologic diagnosis, but also to help in subsequent treatment plan.