- Is this a diffuse or nodular pattern?
This is a diffuse pattern.
- At high magnification, compare the neoplastic cells to the few remaining normal lymphocytes present.
At higher power, the malignant lymphoid cells are much larger than the few remaining small lymphocytes in this lesion. The neoplastic lymphoid cells have a moderately abundant cytoplasm, and the nuclei are round to ovoid with prominent eosinophilic nucleoli.
- What is your diagnosis in this case?
The diagnosis is diffuse large B-cell lymphoma (DLBCL) in the WHO classification. This is histologically a high grade, aggressive lymphoma, but it tends to be localized and have a low stage. It is potentially curable in some patients with disease that is limited to a single mass lesion. Some DLBCL cases arise in persons with primary or secondary immunodeficiency states, such as AIDS.
- What special studies could be done with this tissue to arrive at a more definitive diagnosis?
The major differential diagnosis in this case would be a metastatic carcinoma. The presence of monoclonal immunoglobulin as demonstrated by immunohistochemical staining would help to confirm this lesion as a malignant lymphoma. It should mark for CD19, CD20, and CD79a. Some DLBCLs have either BCL6 mutations or BCL2 overexpression.
If immunohistochemical staining demonstrated cytokeratin positivity, then this would be evidence for a carcinoma. Cytokeratin is present in most carcinomas, but not in lymphomas. Electron microscopy may aid in differentiating carcinoma from lymphoma.
