Primary Mediastinal Large B-Cell Lymphoma and Its Mimickers: A Rare Case Report With Literature Review

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.

Apoptotic Activities in Soft Tissue Sarcoma: Immunohistochemical Study and Their Association with Tumour Characteristics

Background: Many studies on the role of apoptosis in cancer development and management have been undertaken. Apoptotic activity depends partly on the balance between anti-apoptotic (Bcl-2) and pro-apoptotic (Bax) activities. This study compared Bcl-2 and Bax expression in the tumour cells and endothelial cells of tumour blood vessels in soft tissue sarcoma, and examined the association of these with tumour characteristics. Methods: A cross sectional (retrospective) study was conducted on 101 cases of various types of soft tissue sarcoma tumour cells and endothelial cells of tumour blood vessels. The immunohistochemical expressions of Bcl-2 and Bax were compared by correlating them according to site, size, depth, tumour margin, lymph node involvement, and histological type. Results: Higher Bax than Bcl-2 expression in tumour cells was observed, although the difference was not statistically significant. There was a significant direct association between Bcl-2 and Bax in tumour cells with endothelial cells. Among tumour characteristics, the only significant correlation was that of the Bcl-2 expression in tumour cells with tumour histological subtypes (synovial sarcoma and leiomyosarcoma). Conclusion: The findings in this study support the role of endothelial cells in the survival and regression of tumour cells in tumour genesis. Therefore, inhibition of endothelial cell survival and activation, or induction of tumour cell apoptosis offers a promising prospect for tumour management.