2 articles
The hallmark of most B-cell neoplasia is proliferation of B-cells and clonal rearrangement of the immunoglobulin gene, which is lambda or kappa light chain restricted. Since fresh tissue is not always available to determine clonality, immunohistochemical (IHC) staining for kappa and lambda light chains is often performed on formalin-fixed, paraffin-embedded (FFPE) tissue. Commercially available polyclonal antibodies typically produce high background staining and have a significant false negative rate, which makes it difficult to prove clonality. We developed a series of monoclonal antibodies to human kappa and lambda light chain constant regions by immunizing mice with purified kappa and lambda immunoglobulin light chains.
Screening of the hybridoma populations and clone selection was performed in two steps. Primary screening was done by ELISA in plates coated with purified human kappa and lambda light chains fixed with 10% formalin. The positive populations were then selected by IHC staining of FFPE containing B-cell neoplasms with known immunophenotype.
We selected eight hybridomas that produced highly specific monoclonal antibodies (mAbs) directed to the constant regions of kappa (four clones) and lambda light chains (four clones). The antibodies were used for IHC staining and direct immunofluorescence microscopy on FFPE tissues. Plasma cell neoplasms could be stained without antigen retrieval. For uniform and reproducible staining of diffuse large B-cell lymphomas and some marginal zone B-cell lymphomas with plasmacytoid differentiation, a heat-based antigen retrieval procedure was necessary. Compared with commercial polyclonal antibodies to kappa and lambda light chains these mAbs demonstrated lower background staining and produced fewer false negative results.
Myeloid sarcomas (MS) are extramedullary manifestations of myeloid neoplasms, associated with conditions like acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), and myeloproliferative neoplasms (MPN). MS presents as tumor masses in various body sites, often expressing myeloid or monocytic markers. This case report details an unusual biphasic MS relapse with a significant "intravascular" component.
A 59-year-old male with a history of JAK2-V617F positive MDS/MPN underwent allogeneic hematopoietic stem cell transplantation and presented with abdominal pain, skin lesions, and systemic symptoms. Biopsy of colonic masses was performed, and subsequent analysis was carried out.
The biopsy revealed a neoplasm with solid and intravascular components. The solid part was mainly composed of monocytic lineage cells expressing specific markers, with a small population of myeloid blasts. In contrast, the "intravascular" component was mainly myeloid blasts expressing different markers. Genetic analysis uncovered JAK2 (V617F) and KRAS (G12C) mutations. Despite treatment, the disease progressed, and the patient eventually passed away.
Myeloid sarcomas are challenging to diagnose, often being mistaken for large cell lymphomas. They can manifest as isolated extramedullary relapses, with a unique molecular profile. This case stands out due to its biphasic nature, featuring distinct components with differing characteristics, which has not been documented previously in English literature. It underscores the intricate and diverse nature of myeloid sarcomas, emphasizing the need for further research to comprehend their biology and behavior effectively.