Composite mantle cell and follicular lymphoma. A case report.

We describe the association of 2 types of small B-cell lymphomas with different morphologic and immunophenotype patterns inside the same lymph node. Morphologically distinct zones were detected and studied with immunohistochemistry analyses. Most of the areas examined were characteristic of classic mantle cell lymphoma (CD20+, CD5+, cyclin D1+) with nodular and mantle zone areas. However, other areas had the morphologic and immunohistochemistry pattern of follicular lymphoma (CD20+, CD10+, Bcl2+). The diagnosis of both lymphomas was confirmed by polymerase chain reaction detection of both Bcl-1 MTC and Bcl-2 MBR rearrangements. DNA degradation in fixed tissue prevented a complete polymerase chain reaction analysis of immunoglobulin heavy chain rearrangements, but a single immunoglobulin H rearrangement was detected at the FR3 locus. These findings confirm the presence of a monoclonal cell population but do not demonstrate the same clonal origin for both lymphoma populations.

The secreted form of dengue virus nonstructural protein NS1 is endocytosed by hepatocytes and accumulates in late endosomes: implications for viral infectivity.

The flavivirus nonstructural protein NS1 is expressed as three discrete species in infected mammalian cells: an intracellular, membrane-associated form essential for viral replication, a cell surface-associated form that may be involved in signal transduction, and a secreted form (sNS1), the biological properties of which remain elusive. To determine the distribution of the dengue virus (DEN) sNS1 protein in vivo, we have analyzed by immunohistological means the tissue tropism of purified DEN sNS1 injected intravenously into adult mice. The sNS1 protein was found predominantly associated with the liver, where hepatocytes appeared to represent a major target cell. We further showed that sNS1 could be efficiently endocytosed by human Huh7 and HepG2 hepatocytes in vitro. After its internalization, the protein was detected intracellularly for at least 48 h without being substantially degraded. Colocalization studies of sNS1 with markers of the endolysosomal compartments revealed that the protein was specifically targeted to lysobisphosphatidic acid-rich structures reminiscent of late endosomes, as confirmed by electron microscopy. Intracellular accumulation of sNS1 in Huh7 cells enhanced the fluid phase uptake of rhodamine-labeled dextran. Furthermore, preincubation of Huh7 cells with sNS1 increased dengue virus production after infection with the homologous strain of DEN-1 virus. Our results demonstrate that the accumulation of DEN sNS1 in the late endosomal compartment of hepatocytes potentializes subsequent dengue virus infection in vitro, raising the possibility that sNS1 may contribute to viral propagation in vivo.

[Rectal endocrine intermediate-cell carcinoma]. / Carcinome endocrine à grandes cellules du rectum.

An 82-year-old patient complained of diarrhea due to a rectal endocrine intermediate-cell carcinoma. Histology displayed a neuron-specific enolase and CD56 immunoreactive tumor. Hepatic metastases developed rapidly and the tumor was briefly reactive to radiotherapy and chemotherapy. These tumors are rare and have a poor prognosis. We focus on the recent classification of gastrointestinal endocrine tumors.