Clinical and magnetic resonance imaging features of compressive cervical myelopathy with traumatic intervertebral disc herniation in cynomolgus macaque (Macaca fascicularis) / 한국실험동물학회지

Intervertebral disc herniation (IVDH) with nucleus pulposus extrusion, traumatic or not, is a devastating clinical condition accompanied by neurological problems. Here we report a cynomolgus macaque suffering from acute and progressive neurological dysfunction by a blunt trauma due to neck collar, an animal handling device. Tetraplegia, urinary incontinence, decreased proprioception, and imperception of pain were shown on physical and neurological examinations. MRI sagittal T2 weighted sequences revealed an extensive protrusion of disc material between C2 and C3 cervical vertebra, and this protrusion resulted in central stenosis of the spinal cord. Histopathologic findings showed a large number of inflammatory cells infiltrated at sites of spinal cord injury (SCI). This case is the first report of compressive cervical SCI caused by IVDH associated with blunt trauma.

Effect of IL-4 on the Development and Function of Memory-like CD8 T Cells in the Peripheral Lymphoid Tissues

Unlike conventional T cells, innate CD8 T cells develop a memory-like phenotype in the thymus and immediately respond upon antigen stimulation, similar to memory T cells. The development of innate CD8 T cells in the thymus is known to require IL-4, which upregulates Eomesodermin (Eomes). These features are similar to that of virtual memory CD8 T cells and IL-4-induced memory-like CD8 T cells generated in the peripheral tissues. However, the relationship between these cell types has not been clearly documented. In the present study, IL-4-induced memory-like CD8 T cells generated in the peripheral tissues were compared with innate CD8 T cells in terms of phenotype and function. When an IL-4/anti-IL-4 antibody complex (IL-4C) was injected into C57BL/6 mice daily for 7 days, the Eomes(hi)CXCR3+ CD8 T cell population was markedly increased in the peripheral lymphoid organs and blood. These cells were generated from naïve CD8 T cells or accumulated via the expansion of pre-existing CD44(hi)CXCR3+ CD8 T cells. Initially, the majority of these CXCR3+ CD8 T cells expressed low levels of CD44, which was followed by the conversion to the CD44(hi) phenotype. This conversion was associated with the acquisition of enhanced effector function. After discontinuation of IL-4C treatment, Eomes expression levels gradually decreased in CXCR3+ CD8 T cells. Taken together, the results of this study demonstrate that IL-4-induced memory-like CD8 T cells generated in the peripheral lymphoid tissues are phenotypically and functionally similar to the innate CD8 T cells generated in the thymus.

Cardiopulmonary effects of thiopental versus propofol as an induction agent prior to isoflurane anesthesia in chair trained rhesus macaques (Macaca mulatta) / 한국실험동물학회지

The purpose of this study was to evaluate the effects of thiopental versus propofol on cardiopulmonary functions, when used as an induction agent prior to isoflurane anesthesia in rhesus monkeys. Eight healthy rhesus monkeys weighing 3.72 to 5.7 kg, 4-5 years old, were used in the study. Anesthesia was induced with thiopental or propofol intravenous injection, and then maintained with isoflurane in oxygen for 45 minutes. Cardiopulmonary measurements were obtained before and 5, 15, 30, 45, and 60 minutes after induction. The induction doses of thiopental and propofol were 19.41±0.54 and 9.33±1.02 mg/kg, respectively. In both groups, the values of heart rate, respiratory rate, temperature, systolic blood pressure, mean blood pressure, diastolic blood pressure, pH, and lactate were decreased, while the values of partial pressure of carbon dioxide, partial pressure of oxygen, total carbon dioxide, bicarbonate, oxygen saturation, and base excess in the extracellular fluid were increased, as compared with baseline. Systolic blood pressure was significantly lower in thiopental group compare to propofol group. Induction time was very short in both agents but not revealed a significant difference between both groups. However, recovery time was extremely faster in the propofol group. Our results demonstrated that propofol provides a minor suppression in systolic arterial blood pressure than thiopental sodium. In addition, propofol have a fast recovery effect from the anesthesia as well. Furthermore, it is suggested that thiopental sodium could also be used to induce anesthesia instead of propofol, despite slight more suppression of cardiopulmonary function compared to thiopental sodium.

Analyses of the TCR repertoire of MHC class II-restricted innate CD4+ T cells

Analysis of the T-cell receptor (TCR) repertoire of innate CD4+ T cells selected by major histocompatibility complex (MHC) class II-dependent thymocyte-thymocyte (T-T) interaction (T-T CD4+ T cells) is essential for predicting the characteristics of the antigens that bind to these T cells and for distinguishing T-T CD4+ T cells from other types of innate T cells. Using the TCRmini Tg mouse model, we show that the repertoire of TCRalpha chains in T-T CD4+ T cells was extremely diverse, in contrast to the repertoires previously described for other types of innate T cells. The TCRalpha chain sequences significantly overlapped between T-T CD4+ T cells and conventional CD4+ T cells in the thymus and spleen. However, the diversity of the TCRalpha repertoire of T-T CD4+ T cells seemed to be restricted compared with that of conventional CD4+ T cells. Interestingly, the frequency of the parental OT-II TCRalpha chains was significantly reduced in the process of T-T interaction. This diverse and shifted repertoire in T-T CD4+ T cells has biological relevance in terms of defense against diverse pathogens and a possible regulatory role during peripheral T-T interaction.

Interaction between the mouse homologue of CD99 and its ligand PILR as a mechanism of T cell receptor-independent thymocyte apoptosis

Here, we show that the interaction between two membrane proteins, the mouse homologue of CD99 (designated D4) and its ligand, paired immunoglobulin-like type 2 receptor (PILR), is one of the major mechanisms of thymocyte apoptosis. Using the polymeric fusion protein of PILR and IgG1 (PILR-Ig), we demonstrated that D4 ligation in the absence of T cell receptor (TCR) engagement leads to the induction of apoptosis, mainly at the double-positive stage of thymocytes. This was further confirmed by a blocking study in which blocking the interaction between D4 and PILR by soluble D4 protein led to reduced apoptosis in the fetal thymic organ culture with wild type and TCRalpha(-/-) mice. Furthermore, the dissection of intracellular signaling pathway demonstrated that D4 cross-linking led to caspase activation without any change in mitochondrial membrane potential. Based on these data, we propose a mechanism for thymocyte depletion in which the interaction between D4 and PILR delivers an active signal.

Immunohistochemical and Molecular Characteristics of Follicular Patterned Thyroid Nodules with Incomplete Nuclear Features of Papillary Thyroid Carcinoma

BACKGROUND: Follicular patterned thyroid nodules with incomplete nuclear features of papillary thyroid carcinoma (FTN-INPTCs) are difficult to diagnose, and their biological behavior and association with follicular variants of PTC (FVPTCs) have not yet been established. The aim of this study is to determine immunohistochemical and molecular characteristics of FTN-INPTCs. METHODS: We investigated immunohistochemical features (galectin-3, HBME-1, CK19, fibronectin-1, CITED1), BRAF V600E mutation and RASSF1A promoter methylation status in 30 FTN-INPTC cases, along with 26 FVPTCs, 21 follicular adenomas (FAs) and 14 nodular hyperplasias (NHs). RESULTS: Expression of galectin-3, HBME-1, CK19 and CITED1 was significantly higher in FTN-INPTCs than in FAs or NHs, but expression of galectin-3, CK19 and fibronectin-1 was lower in FTN-INPTCs than in FVPTCs. The BRAF V600E mutation was not detected in the benign nodules or FTN-INPTCs, whereas 57% of FVPTCs had the mutation. RASSF1A promoter methylation was higher in FTN-INPTCs than in benign nodules but there was no difference between FTN-INPTCs and FVPTCs. CONCLUSIONS: Our results represent the borderline immunohistochemical and molecular characteristics of FTN-INPTC. We conclude that FTN-INPTC is an intermediate lesion between a benign nodule and a FVPTC, and that it is pathogenetically related to FVPTC.

Diagnostic Value of Galectin-3, HBME-1, Cytokeratin 19, High Molecular Weight Cytokeratin, Cyclin D1 and p27(kip1) in the Differential Diagnosis of Thyroid Nodules

The distinction between benign and malignant thyroid tumors is critical for the management of patients with thyroid nodules. We applied immunohistochemical staining for galectin-3, HBME-1, cytokeratin 19 (CK19), high molecular weight cytokeratin (HMWCK), cyclin D1 and p27(kip1) in 295 thyroid lesions to determine their diagnostic accuracy. The expression of all markers was significantly associated with differentiated thyroid carcinoma (DTC).The sensitivity for the diagnosis of DTC was 94.7% with galectin-3, 91.3% with HBME-1, and 90.3% with CK19. The specificities of these markers were 95.5%, 69.7%, and 83.1%, respectively. Combining these markers, co-expression of galectin-3 and CK19 or galectin-3 and HBME-1 was seen in 93.2% of carcinomas but in none of the benign nodules. Comparing follicular variant of papillary carcinoma (FVPC) with follicular carcinoma (FC), the expression of galectin-3, CK19, and HMWCK was significantly higher in FVPC. When comparing FC with FA, the expression of galectin-3 and HBME-1 was significantly higher in FC. These results suggest that 1) galectin-3 is a useful marker in the distinction between benign and malignant thyroid tumors, 2) the combined use of HBME-1 and CK19 can increase the diagnostic accuracy, and 3) the use of CK19 and HMWCK can aid in the differential diagnosis between PC and FC.

CD99 activates T cells via a costimulatory function that promotes raft association of TCR complex and tyrosine phosphorylation of TCR zeta

We investigated the co-stimulatory role of a cell-surface protein, CD99. Co-ligation of CD99 and suboptimal CD3 induced T-cell activation to a level comparable to that obtained with optimal CD3 or CD3+CD28. We also noted concomitant enhancement of the earliest T-cell receptor (TCR) signaling events. In addition, co-ligation of CD99 and CD3 led to translocation of TCR complexes into the lipid raft, without concomitant migration of CD99 to the raft, and consequent enhancement of TCR zeta-mediated signal 1. These data demonstrate the unique properties of CD99 co-stimulation that distinguish this molecule from CD28 and other raft-resident co-stimulatory factors.

Expressions of Id-1 and Id-2 in Hyperplastic Thyroid Tissue and Thyroid Carcinoma

BACKGROUND: Id proteins are a family of helix-loop-helix proteins and are regarded to be negative regulators of cell differentiation. In general, Id-1 and Id-2 expressions are upregulated during tumor development and progression in a variety of neoplasms, and these expressions may be associated with aggressive tumor behavior. However, little is known about the roles of Id-1 and Id-2 in thyroid neoplasms. METHODS: The expressions of Id-1 and Id-2 were assessed immunohistochemically in 310 normal, hyperplastic, and neoplastic thyroid tissues using tissue microarrays. RESULTS: Normal thyroid tissues rarely expressed Id-1 or Id-2. Moreover, whilst Id-1 expression was more elevated in malignant thyroid tissue than in hyperplastic thyroid tissue, Id-2 expression was more variable. No significant differences were observed between histologic subtypes of thyroid carcinomas with respect to Id-1 or Id-2 expression. Follicular adenomas showed higher expressions of Id-1 and Id-2 than thyroid carcinomas. No significant association was found between clinicopathological parameters and Id-1 expression, though Id-2 expression was significantly reduced in metastatic, stage IV tumors. CONCLUSION: The expressions of Id-1 and Id-2 were elevated in hyperplastic and neoplastic thyroid tissues. However, neither appears suitable as a marker of malignancy or an aggressive phenotype, although Id-2 expression in advanced thyroid carcinomas may reflect a favorable prognosis.

Survivin and Fas Ligand Expressions Are Correlated with Angiolymphatic Tumor Spread in Medullary Thyroid Carcinoma

BACKGROUND: Medullary thyroid carcinoma (MTC) that originates from C cells comprises about 10% of all the malignant thyroid tumors. Activating mutations of the RET proto-oncogene have been found to be involved in the anti-apoptotic pathway of MTC that harbors the RET mutation. We investigated the correlation between the clinicopathologic parameters and the expressions of survivin, a novel anti-apoptotic molecule, and the other apoptosis-related proteins, and the known prognostic markers. METHODS: Immunohistochemical staining was performed using antibodies for survivin, Fas, Fas ligand (FasL), bcl-2, calcitonin, CEA and cyclin A in 19 case of MTC; 10 sporadic MTCs, eight multiple endocrine neoplasia (MEN) type 2A MTCs and one familial MTC (FMTC). RESULTS: Survivin protein expression was found in five cases (26%) and this was correlated with the presence of angiolymphatic tumor emboli (p=0.019). FasL was expressed in 14 cases (74%) and it had correlation with the presence of lymph node metastases (p=0.029). The cyclin A-labeling indices were correlated with local invasiveness (p=0.001). CONCLUSIONS: Survivin and FasL might be involved in the lymphatic tumor spread of MTC.

Immunohistochemical Analysis of Insular Carcinoma of the Thyroid Gland

BACKGROUND: Insular thyroid carcinoma (ITC) is a relatively infrequent thyroid carcinoma that has distinctive histologic features. ITC shows an aggressive clinical course and the predominant presence of an insular component, which has been reported to be an independent factor of a poor prognosis. We retrospectively examined clinical details of the nine ITC patients, which represented 9 years of experience with ITC, and investigated the expressions of variable neuroendocrine and other immunohistochemical markers associated with well-differentiated thyroid carcinomas. METHODS: We adopted an immunohistochemical approach and studied the expressions of synaptophysin, chromogranin A, CD56, NSE, S-100, RET, PPARgamma, calcitonin, galectin-3, and thyroglobulin in formalin-fixed, paraffin embedded tissue array slides of the 9 ITC patients, and investigated clinical features. Seven cases of follicular carcinoma and 4 cases of medullary carcinoma were also included as controls. RESULTS: ITCs were positive for synaptophysin (44%, 4/9), CD56 (11%, 1/9), NSE (89%, 8/9), S100 (67%, 6/9), calcitonin (22%, 2/9), galectin-3 (78%, 7/9), and thyroglobulin (100%, 9/9), but completely negative for chromogranin A, RET, and PPARgamma. CONCLUSION: ITCs express neuroendocrine markers in variable proportions and appear not to be associated with the oncoproteins of conventional thyroid carcinomas. Notably, its differential diagnosis from medullary carcinoma is required in cases showing focal calcitonin positivity.

Two Cases of Primary Small Cell Carcinomas of the Stomach

Primary small-cell carcinomas of the stomach are rare and aggressive malignancies with poor survival rates. Preoperative diagnosis is difficult and a standard treatment is not yet established. We have recently experienced two cases of a primary small-cell carcinoma of the stomach. The first case was a 65-year-old man with epigastric soreness. Endoscopic biopsy showed an adenocarcinoma. He underwent a radical subtotal gastrectomy with D2 lymph-node dissection. Pathology revealed a collision tumor of a small- cell carcinoma and an adenocarcinoma with submucosal invasion and with metastasis in 20 out of 48 lymph nodes (T1N3M0). The second case was a 64-year-old man with epigastric soreness. Endoscopic biopsy revealed a small-cell carcinoma. There was no evidence of a primary tumor in the lung. A radical subtotal gastrectomy with D2 lymph-node dissection was performed. Pathology showed a pure small- cell carcinoma with proper muscle invasion and with metastasis in 1 out of 36 lymph nodes (T2aN1M0).

Hyalinizing Trabecular Adenoma of Thyroid

The Hyalinizing trabecular adenoma of the thyroid is a uncommon benign neoplasm which is characterized by trabecular growth pattern with hyaline stroma of the basal membrane type. It is often misdiagnosed as papillary carcinoma due to its peculiar cytologic and histologic features such as, nuclear grooving and papillary structures, or as medullary carcinoma due to the hyalinized stroma resembling amyloid. Special stains and immunohistochemical studies are required to make a definite diagnosis. A 34-year old woman was admitted suffering from a left neck mass. Computed tomography showed a 2 cm-sized mass in the left thyroid. Fine needle aspiration cytology suggested papillary carcinoma. Intraoperative frozen section suggested medullary carcinoma, and H&E staining suggested medullary carcinoma. However according to immunohistochemistry which revealed calcitonin negative, the tumor was reviewed and finally diagnosed as hyaline trabecular adenoma. The hyalinizing trabecular adenoma, although uncommon, is certainly worth consideration in order to avoid being misinterpreted as carcinoma on the basis of individual cytologic and histologic features.

CD99 type II is a determining factor for the differentiation of primitive neuroectodermal cells

CD99 is a 32-kDa cell surface molecule present on thymocytes, peripheral T cells, many other hematopoietic stem cells and somatic cells were implicated in cell-cell adhesion and cell-activation phenomena. Two major subtypes have been identified so far, designated CD99 type I and type II. We have investigated the correlation between the degree of neural differentiation and the expression of CD99 subtypes in three differentially differentiated cell lines such as CADO-ES1, RD-ES, and SH-N-SY5Y, in order of differentiation. In addition, we induced differentiation of the RD-ES cell line by N(6),2'-dibutyryl-cAMP (db-cAMP). Six days after treatment with db-cAMP, RD-ES cell line has changed its morphology from uniform round cells to cells with neurites, and initially CD99 type II-overexpressed RD-ES cells showed significant down-regulation of CD99 type II, whereas CD99 type I expression remained constant. When RD- ES cells were transfected with the cDNA encoding for CD99 type I-green fluorescence protein (GFP) and type II-GFP, CD99 type II transfected RD-ES cell line remained unchanged with morphology of undifferentiated form. Our data suggest that CD99 type II acts as a negative regulator in the neural differentiation of precursor cells that might occur during nerve system development.

Immunoreactivity of CD99 in Stomach Cancer

CD99 is characteristically expressed in Ewing's sarcoma/primitive neuroectodermal tumor. Recently its immunoreactivity has also been reported in other tumors. However, the significance of CD99 isoforms expressed in these tumors has not been elucidated. In this study, we evaluated the expression of CD99 isoforms and its relationship with histopathologic parameters in gastric adenocarcinomas. Paraffin sections of 46 gastric adenocarcinomas were stained with an anti-CD99 monoclonal antibody, YG32. Twelve (26.1%) cases of 46 gastric adenocarcinomas showed immunoreactivity to YG32. The CD99 expression was also seen both in non-neoplastic foveolar epithelial cells and infiltrating lymphocytes. In addition, Western blot and RT-PCR analyses revealed that the type I is the predominant isoform of CD99 in non-neoplastic and neoplastic gastric tissues. The CD99 expression was usually seen in the intestinal type adenocarcinoma, while rarely in the diffuse type. The CD99 immunoreactivity decreased in MMP-2-overexpressing adenocarcinomas (p=0.028). Our results suggest that the type I is the major isoform of CD99 expressed in non-neoplastic gastric mucosa and gastric adenocarcinomas and its downregulation in gastric adenocarcinoma may be associated with cellular dedifferentiation and/or MMP-2 overexpression.

Characterization and epitope mapping of two monoclonal antibodies against human CD99

CD99 plays an critical role in the diapedesis of monocytes, T cell differentiation, and the transport of MHC molecules. Engagement of CD99 by agonistic monoclonal antibodies has been reported to trigger multifactorial events including T cell activation as well as cell-cell adhesion during hematopoietic cell differentiation. In this study, to identify the functional domains participating in the cellular events, we mapped the epitopes of CD99, which are recognized by two agonistic CD99 monoclonal antibodies, DN16 and YG32. Using recombinant fusion proteins of GST with whole or parts of CD99, we found that both antibodies interact with CD99 molecules independently of sugar moieties. DN16 mAb detected a linear epitope located in the amino terminal region of CD99 while YG32 mAb bound another linear epitope in the center of the extracellular domain. To confirm that the identified epitopes of CD99 are actually recognized by the two mAbs, we showed the presence of physical interaction between the mAbs and the fusion proteins or synthetic peptides containing the corresponding epitopes using surface plasmon resonance analyses. The dissociation constants of DN16 and YG32 mAbs for the antigen were calculated as 1.27 X 10(-7) and 7.08 X 10(-9) M, respectively. These studies will help understand the functional domains and the subsequent signaling mechanism of CD99.

Functional involvement of src and focal adhesion kinase in a CD99 splice variant-induced motility of human breast cancer cells

Earlier report showed that expression of a splice variant of CD99 transmembrane protein increases invasive ability of human breast cancer cells. Cell motility was also significantly enhanced by the CD99 splice variant expression. In an effort to identify the cellular components that mediate a signal transduction pathway triggered by the CD99 splice variant, known signal path inhibitors were examined for their effects on the motility of the CD99 splice variant-transfected MDA-MB-231 breast cancer cells. Phenylarsine oxide, an inhibitor of phosphatase specific for focal adhesion kinase, and PP1, an inhibitor of src kinase family, significantly suppressed motility of the cells. Among different types of src transfectant clones generated, kinase-negative mutant src transfectant cells were 80% less motile than the mock cells transfected with an empty-vector, while v-src and c-src transfectants exhibited cell motility levels at or slightly above the mock transfectant. These results suggest that src and focal adhesion kinase mediate the intracellular signaling pathway of a CD99 splice variant for the induction of motility of human breast cancer cells.

Immature thymocyte antigen, JL1, as a possible immunodiagnostic and immunotherapeutic target for leukemia

The identification of tumor-specific antigens has represented a critical milestone in cancer diagnosis and therapy. Clinical research in this area for leukemia has also been driven over the past few decades by the hope that surface antigens with restricted tissue expression would be identified. Disappointingly, only a small number of the leukemic antigens identified to date, meet sufficient criteria to be considered viable immunophenotypic markers. In this paper, we nominate anti-JL1 monoclonal antibody as an immunodiagnostic and immunotherapeutic candidate for leukemia. The JL1 molecule appears to be a novel cell surface antigen, which is strictly confined to a subpopulation of limited stages during the hematopoietic differentiation process. Despite the restricted distribution of the JL1 antigen in normal tissues and cells, anti-JL1 monoclonal antibody specifically recognizes various types of leukemia, irrespective of immunophenotypes. On the basis of these findings, we propose JL1 antigen as a tumor-specific marker, which shows promise as a candidate molecule for diagnosis and immunotherapy in leukemia, and one that spares normal bone marrow stem cells.

Expression of the G1-S Modulators in Hepatitis B Virus-Related Hepatocellular Carcinoma and Dysplastic Nodule: Association of Cyclin D1 and p53 Proteins with the Progression of Hepatocellular Carcinoma

Deranged expression of cell cycle modulators has been reported to contribute to the development and progression of hepatocellular carcinoma (HCC). However, their expression patterns remain poorly understood in hepatitis B virus (HBV)-related HCC, which constitutes about 65-70% of HCC in Korea. The aims of this study were to evaluate the expressions of G1-S modulators in HBV-related HCCs and dysplastic nodules (DNs), and to correlate with the histopathologic features of HCCs. Immunohistochemical expressions of cyclin D1, cyclin E, p53, p27, p21, p16, Rb, and PCNA proteins were investigated in 80 HCCs and 22 DNs. Cyclin D1 overexpression showed positive relationships with advanced tumor stage, poor differentiation, larger tumor size, microvascular invasion, intrahepatic meta-stasis, no tumor capsule formation, infiltrative growth, aberrant p53 expression, and high PCNA labeling index (LI) of HCC (p<0.05). Aberrant p53 expression showed positive relationship with poor differentiation of HCC (p<0.01). Expression of cyclin D1 or p53 was not observed in DNs. The p27 LI and p16 LI were lower in HCCs with intrahepatic metastasis (p<0.05). Cyclin D1 overexpression and aberrant p53 expression could be associated with the progression of HBV-related HCC, and might have a less crucial role in the DN-HCC sequence. In addition, elevated expression of p27 and p16 proteins might have inhibitory action to the intrahepatic metastasis of HBV-related HCC.

The Increased Expression and Diagnostic Usefulness of CD56 Antigen in Paraffin Embedded Plasma Cell Neoplasm

BACKGROUND: The natural killer cell antigen CD56 (NCAM) is a member of the immunoglobulin superfamily and is expressed on neurons, astrocytes, and Schwann cells. Recently, it has been reported that CD56 expression is detected on plasma cells of multiple myeloma by flow cytometry. METHOD: In this study, to test the diagnostic usefulness of the anti-CD56 antibody for plasma cell neoplasm on paraffin-embedded materials, we performed immunohistochemical staining of samples from 19 patients with plasma cell neoplasms. These cases included 14 cases of multiple myeloma, 3 cases of solitary plasmacytoma of the bone, and two cases of extramedullary plasmacytoma. RESULTS: The neoplastic plasma cells from 68 % of the patients with plasma cell neoplasms expressed CD56 highly. CD56 was expressed in all three cases of solitary plasmacytoma of the bone and one of two extramedullary plasmacytoma, and nine out of 14 multiple myeloma cases. In contrast, reactive plasma cells from the 18 patients with miscellaneous lesions were completely negative for CD56. CONCLUSIONS: CD56 is aberrantly expressed on the neoplastic plasma cells, and it may be used as a useful marker for the diagnosis of plasma cell neoplasms in paraffin-embedded tissues.