Expression of VS38 in osteoblasts and stroma cells of bone tumors

Limitations of VS38c labeling in the detection of plasma cell myeloma by flow cytometry

Plasma cell myeloma (multiple myeloma [MM]) is a malignant neoplasm originating from the plasma cells. Besides other methods, flow cytometric analysis of the patient's bone marrow aspirate has an important role in the diagnosis and also in the response assessment. Since the cell surface markers, used for identifying abnormal plasma cells, are expressed diversely and the treatment can also alter the phenotype of the plasma cells, there is an increasing demand for new plasma cell markers. VS38c is a monoclonal antibody that recognizes the CLIMP-63 protein in the membrane of the endoplasmic reticulum. CLIMP-63 is known to be expressed at high levels in normal and pathologic plasma cells in the bone marrow, thus VS38c antibody can be used to identify them. Although VS38c staining of plasma cells is reported to be constant and strong even in myeloma, we were wondering whether sample preparation can affect the staining. We have investigated the effect of different permeabilization agents and washing of the cells on the quality of the VS38c staining and found that in many cases the staining is inadequate to identify the plasma cells. We measured the VS38c staining of the bone marrow aspirates of 196 MM patients and observed that almost all cases showed bright staining with VS38c. However, permeabilization with mild detergent resulted in the appearance of a significant VS38c^dim subpopulation, which showed increased sensitivity to mechanical stress (centrifugation). Our results indicate that VS38c^dim MM cells can appear due to the improper permeabilization of the endoplasmic reticulum and this finding raises the possibility of the existence of a plasma cell subpopulation with different membrane properties. The significance of this population is unclear yet, but these cells can be easily missed with VS38c staining and can be lost due to centrifugation-induced lysis during sample preparation.

VS38 staining contributes to a novel gating strategy in flow cytometry for small B cell lymphoma, especially in lymphoplasmacytic lymphoma/Waldenström macroglobulinemia

BACKGROUND

Multi-parametric flow cytometry (MFC) is a helpful tool for detecting neoplastic cells in malignant lymphoma; however, lymphoma cells can be difficult to detect when characteristic immunophenotypic abnormalities are not evident. We evaluated the stainability of VS38, which is used for multiple myeloma, in normal and abnormal B cells using MFC to develop a new strategy for detecting lymphoma cells.

METHODS

We compared the median fluorescence intensity of VS38 staining in lymphocytes from patients without hematopoietic neoplasms and in B cells from 26 patients with B cell lymphoma (BCL). To evaluate the performance of VS38 gating, we compared VS38-positive B cells with the percentages of BCL cells, and with the mutation ratios of MYD88 L265P measured by droplet digital PCR in patients with lymphoplasmacytic lymphoma (LPL)/Waldenström macroglobulinemia (WM).

RESULTS

CD27-positive memory B cells were stained with VS38, whereas normal lymphocytes were faintly stained. Lymphoma cells were stained with VS38 in 11 of 12 patients with LPL/WM, 3 of 3 with chronic lymphocytic leukemia, 3 of 5 with mantle cell lymphoma, 2 of 4 with follicular lymphoma, and 1 of 1 with splenic marginal zone lymphoma. The percentages of VS38-positive B cells in VS38-positive BCL were equivalent to those of lymphoma cells and the mutation ratios of MYD88 L265P in LPL/WM.

CONCLUSIONS

VS38 identified neoplastic cells in plasma cell disorders and BCL. This might improve the accuracy of BCL diagnosis, especially in patients with LPL/WM.

VS38 Identifies Myeloma Cells With Dim CD38 Expression and Plasma Cells Following Daratumumab Therapy, Which Interferes With CD38 Detection for 4 to 6 Months

OBJECTIVES

We report our institutional experience using VS38 to evaluate plasma cells by flow cytometry.

METHODS

Flow cytometry data were reanalyzed to compare plasma cell percentages between the standard panel and VS38 panel. Natural killer (NK) and plasma cell CD38 median fluorescence intensity (MFI) values were calculated.

RESULTS

Our cohort included 63 specimens from 38 patients. Twenty-six had received daratumumab (monoclonal anti-CD38 therapy) between less than 1 month and 17 months prior. For NK and plasma cells, CD38 MFI values were suppressed for 0 to 4 months and started to increase 4 to 6 months after last exposure. There was no significant difference in clonal plasma cell percentage calculated by the VS38 and standard panels; however, identification and quantification using the VS38 panel were easier.

CONCLUSIONS

VS38 is a viable alternative to bright CD38 to identify plasma cells and particularly helpful in myeloma cases with dim CD38 and after daratumumab. Daratumumab interference with CD38 identification persists 4 to 6 months after the last exposure.

Young Adult With Osteosarcoma of the Mandible and the Challenge in Management: Review of the Pediatric and Adult Literatures

Neoadjuvant chemotherapy for osteosarcoma of the jaw (OSJ) remains controversial despite being a standardized treatment in osteosarcoma of the long bones. We present a case of a 22-year-old male with OSJ and performed a retrospective systemic review of previously published literatures of OSJ. We identified 27 articles: 7% recommended neoadjuvant chemotherapy, 22% recommended adjuvant chemotherapy, 19% recommended both neoadjuvant and adjuvant chemotherapy, 33% recommended against chemotherapy and 19% stated the role of chemotherapy is unknown. The lack of consensus regarding the use of chemotherapy in OSJ, despite its benefits, demonstrates the need to establish a standardized algorithm for OSJ.

Utility of VS38c in the diagnostic and prognostic assessment of osteosarcoma and other bone tumours/tumour-like lesions

Background

VS38c is a monoclonal antibody that recognises a rough endoplasmic reticulum (rER) intracellular antigen termed cytoskeleton-linking membrane protein 63. rER is typically found in viable tumour cells and is abundant in osteosarcoma cells. The aim of this study was to determine the diagnostic and prognostic utility of VS38c in the histological assessment of osteosarcoma and other bone tumours/tumour-like leisons.

Methods

Immunohistochemical staining with VS38c was carried out on formalin-fixed specimens of osteosarcoma (pre/post-chemotherapy) and a wide range of benign and malignant bone lesions. In addition, VS38c staining of cultures of MG63 and Sa0S2 osteosarcoma cell cultures. (±cisplatin and actinomycin D-treatment) was analysed.

Results

VS38c strongly stained tumour cells in all low-grade and high-grade osteosarcomas and in undifferentiated sarcomas and high-grade chondrosarcomas. There was little or no VS38c staining of low-grade chondrosarcomas or chordomas and variable staining of Ewing sarcomas. Osteoblasts in benign bone-forming tumours and mononuclear stromal cells in chondroblastomas, giant cell tumours and non-ossifying fibromas strongly stained for VS38c. VS38c staining was absent in cisplatin and actinomycin D treated Sa0S2 and MG63 cells. In specimens of osteosarcoma post-neoadjuvant therapy, VS38c staining was absent in most morphologically necrotic areas of tumor although some cells with pyknotic nuclei stained for VS38c in these areas. Most tumour cells exhibiting atypical nuclear forms were not stained by VS38c.

Conclusions

Our findings show that VS38c is a sensitive but not specific diagnostic marker of osteosarcoma. Staining with VS38c identifies viable osteosarcoma cells, a feature which may be useful in the assessment of percentage tumour necrosis post-neoadjuvant chemotherapy.

Update on the Diagnosis and Classification of the Plasma Cell Neoplasms

The plasma cell neoplasms are malignancies of the most terminally differentiated cells in B-cell ontogeny and are usually associated with the production of a monoclonal immunoglobulin molecule or M protein. These malignancies include tumors whose clinical manifestations are directly attributable to the end-organ damage induced by the dysregulated proliferation of neoplastic plasma cells. In contrast, disorders, such as primary amyloidosis, have a paradoxically low burden of neoplastic plasma cells, rendered highly pathogenic by the end-organ damage induced by deposition of the secreted paraprotein. In this article, discussion focuses on plasma cell myeloma. The molecular pathogenesis of plasma cell myeloma is reviewed and the diagnosis of the plasma cell neoplasms discussed.

Epithelioid osteosarcoma of the mandible: a rare case with unusual immunoprofile

A 42-year-old woman presented a large, nontender, quickly progressive mass in the left mandible. Radiograph showed extensive destruction of the angle, posterior body, and ramus of the left side of the mandible. The patient was surgically treated by hemimandibulectomy. Microscopically, the tumor was composed of large epithelioid cells, many of them showing polarized nuclei, and evident eosinophilic cytoplasm. The predominant pattern was trabecular, and rosette-like structures were also observed. Typical osteoid-containing cells surrounded by malignant cells were found in a few areas. Immunohistochemistry for a large panel of antibodies showed positivity for osteocalcin, osteonectin, osteopontin, VS38c, and S-100. CD34 saliented the hemangiopericytoma-like distribution of the blood vessels. Collagen I was focally positive for the extracellular matrix and malignant osteoid. All other markers were negative, including vimentin and cytokeratins. To the best of our knowledge, this is the first case of epithelioid osteosarcoma affecting the mandible and the second case affecting the jaws that has been reported in the literature.

Diffuse large B-cell lymphomas with plasmablastic differentiation

Recent evidence suggests that diffuse large B-cell lymphoma (DLBCL) with plasmablastic differentiation represents a clinically heterogeneous spectrum with different clinicopathologic characteristics representing distinct entities. Subtypes of DLBCL with plasmablastic features and terminal B-cell differentiation include plasmablastic lymphoma (PBL) of oral mucosa type; PBL with plasmacytic differentiation; primary effusion lymphoma (PEL); KSHV-positive solid lymphoma/extracavitary PEL/HHV-8 associated DLBCL; and DLBCL expressing ALK. In contrast, PBL associated with multicentric Castleman disease, DLBCL with secretory differentiation, pyothorax-associated lymphoma, and atypical Burkitt lymphoma with plasmacytoid differentiation have morphologic appearances of plasma cell differentiation but maintain a mature B-cell (CD20 positive) phenotype. These tumors as well as extramedullary plasmablastic tumors secondary to multiple myeloma or plasmacytomas are included in the differential diagnosis. In this review, we discuss recently described clinicopathologic insights, case observations, and recently reported molecules involved in terminal B-cell or plasma cell differentiation and their possible roles in disease pathogenesis.

Analysis of MUM1/IRF4 protein expression using tissue microarrays and immunohistochemistry

The gene encoding MUM1 was characterized as a possible translocation partner in chromosomal abnormalities involving a significant number of multiple myelomas. The overexpression of the MUM1 protein as a result of translocation t(6;14) (p25;q32) identified MUM1 as a putative regulatory molecule involved in B-cell differentiation and tumorigenesis. The expression of MUM1 protein in multiple myelomas supports this hypothesis. In the current study, using tissue microarray technology, we have tested the expression of the MUM1 protein in 1335 human malignancies and normal tissues. Our data show that the MUM1 protein is expressed in a wide spectrum of hematolymphoid neoplasms and in malignant melanomas but is absent in other human tumors. In addition, in tissue microarrays as well as in conventional paraffin sections, MUM1 staining was found to lack specificity in detecting plasmacytic differentiation as compared with two markers, CD138/Syndecan and VS38, commonly used in paraffin immunohistochemistry for detection of plasma cells.