[Is it possible to individualize microvillous large-cell lymphoma among sinusoid lymphomas?]

Microvillous non-hodgkin lymphomas are large cell malignant lymphomas with a sinus growth pattern and the presence of cytoplasmic processes detected by electron microscopy. Microvillous non-hodgkin lymphomas appear to be of B cell lineage. Neoplasms considered in the differential diagnosis include anaplastic large cell Ki-1 lymphomas, malignant histiocytosis and metastatic carcinoma or malignant melanoma. A panel of markers are usually sufficient to recognize all of these neoplasms except microvillous lymphomas. We report a case of microvillous non-hodgkin lymphoma characterized by a histologic pattern mimicking those of anaplastic large cell Ki-1 lymphoma. However, immunohistochemistry study failed to demonstrate presence of activation antigen such as Ki-1, EMA, interleukin 2 receptor. Ultrastructural study showed that neoplastic cells exhibited filliform cytoplasmic processes. This report raise the possibility of an overlap between microvillous non-hodgkin lymphomas and anaplastic large cell Ki-1 lymphomas of B-cell lineage. It must be emphasized that, initially, these two kinds of lymphomas were defined with different morphologic technologies.