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.
Thymoma is a rare mediastinal tumour that can be accompanied by different paraneoplastic syndromes. Here we report a case of Type A thymoma associated with relapsing minimal change disease (MCD). This case highlights: (1) The need to balance rapid prednisolone weaning against risk for relapse in an elderly patient at risk for steroid-induced complications. (2) The addition of calcineurin inhibitor in relapsed thymoma-related MCD, to achieve steroid sparing effects. Resection of the offending tumour and prompt immunosuppressive therapy are critical in getting best renal and overall outcomes in this rare entity.
A 19-mo-old Holstein heifer was inactive and dyspneic. Physical examination revealed wheezing, exophthalmos, a cervical mass, and lymphadenopathy. Cytology of the cervical mass and lymph nodes showed predominantly large atypical lymphocytes. Lactate dehydrogenase and thymidine kinase activities were elevated. Although nested PCR for bovine leukemia virus (BLV) using blood was positive, quantitative PCR showed a low number of provirus copies. Autopsy revealed enlargement of most lymph nodes examined, as well as white masses of various sizes in muscles of the left hindlimb and thoracic and abdominal organs. Histopathology revealed severe infiltration with neoplastic lymphocytes in these organs. The cervical mass was immune-positive for B-cell markers. The final diagnosis was thymic B-cell lymphoma with BLV infection.