The benign nature and rare occurrence of cardiac myxoma as a possible consequence of the limited cardiac proliferative/ regenerative potential: a systematic review

BACKGROUND

Cardiac Myxoma is a primary tumor of heart. Its origins, rarity of the occurrence of primary cardiac tumors and how it may be related to limited cardiac regenerative potential, are not yet entirely known. This study investigates the key cardiac genes/ transcription factors (TFs) and signaling pathways to understand these important questions.

METHODS

Databases including PubMed, MEDLINE, and Google Scholar were searched for published articles without any date restrictions, involving cardiac myxoma, cardiac genes/TFs/signaling pathways and their roles in cardiogenesis, proliferation, differentiation, key interactions and tumorigenesis, with focus on cardiomyocytes.

RESULTS

The cardiac genetic landscape is governed by a very tight control between proliferation and differentiation-related genes/TFs/pathways. Cardiac myxoma originates possibly as a consequence of dysregulations in the gene expression of differentiation regulators including Tbx5, GATA4, HAND1/2, MYOCD, HOPX, BMPs. Such dysregulations switch the expression of cardiomyocytes into progenitor-like state in cardiac myxoma development by dysregulating Isl1, Baf60 complex, Wnt, FGF, Notch, Mef2c and others. The Nkx2-5 and MSX2 contribute predominantly to both proliferation and differentiation of Cardiac Progenitor Cells (CPCs), may possibly serve roles based on the microenvironment and the direction of cell circuitry in cardiac tumorigenesis. The Nkx2-5 in cardiac myxoma may serve to limit progression of tumorigenesis as it has massive control over the proliferation of CPCs. The cardiac cell type-specific genetic programming plays governing role in controlling the tumorigenesis and regenerative potential.

CONCLUSION

The cardiomyocytes have very limited proliferative and regenerative potential. They survive for long periods of time and tightly maintain the gene expression of differentiation genes such as Tbx5, GATA4 that interact with tumor suppressors (TS) and exert TS like effect. The total effect such gene expression exerts is responsible for the rare occurrence and benign nature of primary cardiac tumors. This prevents the progression of tumorigenesis. But this also limits the regenerative and proliferative potential of cardiomyocytes. Cardiac Myxoma develops as a consequence of dysregulations in these key genes which revert the cells towards progenitor-like state, hallmark of CM. The CM development in carney complex also signifies the role of TS in cardiac cells.

Crosstalk between KIF1C and PRKAR1A in left atrial myxoma

Cardiac myxoma (CM) is the most common benign cardiac tumor, and most CMs are left atrial myxomas (LAMs). Six variations of KIF1C, c.899 A > T, c.772 T > G, c.352 A > T, c.2895 C > T, c.3049 G > A, and c.*442_*443dup in left atrial myxoma tissues are identified by whole-exome sequencing (WES) and Sanger sequencing. RNA-seq and function experiments show the reduction of the expression of KIF1C and PRKAR1A caused by rare variations of KIF1C. KIF1C is observed to be located in the nucleus, bind to the promoter region of PRKAR1A, and regulate its transcription. Reduction of KIF1C decreases PRKAR1A expression and activates the PKA, which causes an increase in ERK1/2 phosphorylation and SRC-mediated STAT3 activation, a reduction of CDH1, TP53, CDKN1A, and BAX, and eventually promotes tumor formation both in vitro and in vivo. The results suggest that inhibition of KIF1C promotes the pathogenesis of LAM through positive feedback formed by the crosstalk between KIF1C and PRKAR1A.

Somatic Mutation of PRKAR1A in Four Cases of Sporadic Cardiac Myxoma

BACKGROUND

Inactivating mutations of the protein kinase A regulatory subunit 1 alpha (PRKAR1A) gene have been reported in familial cardiac myxoma. However, the role of PRKAR1A mutation in sporadic cardiac myxoma remains unknown.

METHODS

Targeted next-generation sequencing (NGS) was performed to identify mutations with the PRKAR1A gene in seven cases of sporadic cardiac myxomas. Sanger sequencing of DNA from cardiac myxoma specimens and matched peripheral blood samples was performed to verify the identified mutations.

RESULTS

Targeted NGS of myxoma DNA revealed 232 single nucleotide variants in 141 genes and 38 insertion-deletion mutations in 13 genes. Six PRKAR1A mutations were identified in four of the seven cardiac myxoma cases, and thus, the PRKAR1A inactivating mutation rate was 57.2% (4/7, 95% CI=0.44-0.58, P<0.05). The PRKAR1A variants identified by Sanger sequencing analysis were consistent with those from the NGS analysis for the four myxoma specimens. All of the pathogenic PRKAR1A mutations led to premature termination of PRKAR1A, except for one synonymous mutation. Moreover, none of the nonsense and missense mutations found in the myxoma specimens were found in the matched peripheral blood samples.

CONCLUSION

Pathogenic mutations of the PRKAR1A gene were identified in tumor specimens from four cases of sporadic cardiac myxoma, and the absence of these mutations in peripheral blood samples demonstrated that they were somatic mutations.

Aggressive angiomyxoma in pregnancy: a case report and literature review

Aggressive angiomyxoma is an interstitial tumour that is often misdiagnosed and is likely to recur. There have been few reported cases of angiomyxoma in pregnant women. We report a case of a woman who was previously diagnosed with a tumour in her vulva that increased in size during both of her pregnancies and spontaneously decreased postpartum. Local excision was performed and a gonadotropin-releasing hormone agonist was administered. According to a literature review, aggressive angiomyxoma is associated with good maternal and child outcomes. Caesarean section is not the delivery method of choice, but it is indicated if the tumour is preventing vaginal birth. Treatment for angiomyxoma is mainly postpartum local resection supplemented by hormone therapy. This tumour frequently recurs and patients should undergo long-term follow-up.

Hypermetabolic Cerebral Metastases of Cardiac Myxoma on FDG PET/CT

ABSTRACT

A 66-year-old woman with a history of surgical resection of left atrial myxoma 6 months ago presented with multiple brain lesions with MRI. An FDG PET/CT was performed for further evaluation. The images showed that cerebral tumors had variable and increased FDG uptake in general, and no other abnormal FDG-avid lesions were noted. The tumor of right occipital lobe was resected and confirmed as metastatic cardiac myxoma on histology.

Conjunctival Myxoid Lesions: Clinical-Pathologic Multiparametric Analysis, Including Molecular Genetics (An American Ophthalmological Society Thesis)

PURPOSE

To evaluate the clinical and pathologic characteristics of conjunctival myxoid lesions, with specific focus on PRKAR1A studies, in order to distinguish neoplastic conjunctival myxoma from other myxoid conjunctival lesions.

METHODS

A retrospective, interventional, multicenter study of all patients with conjunctival myxoma, conjunctival stromal tumor, or reactive fibromyxoid proliferation diagnosed during 1988-2018. Patient and family medical histories and clinical and pathologic characteristics of excised lesions were assessed.

RESULTS

There were 28 patients with conjunctival myxoid lesions diagnosed as myxoma (16/28), conjunctival stromal tumor (10/28), or reactive fibromyxoid proliferation (2/28). The patients with abundant myxoid matrix lesions (14/28, 50%) were younger (mean 49 [range 23-68] years) than those with scant-to-moderate myxoid matrix lesions (14/28, mean 61 [range 18-82] years; P = .04). Abundant myxoid matrix lesions more likely contained predominantly stellate cells (6/14 [43%] vs 0/14 [0%]; P = .05) and fibrillar collagen (13/14 [93%] vs 2/14 [14%]; P < .0001), conforming to the standard morphologic definition of myxoma. Absence of PRKAR1A protein expression was found in 2 lesions with morphologic features of myxoma (2/14, 14%), 1 of which demonstrated a pathogenic mutation in the PRKAR1A gene. There was no difference between the lesions with respect to other clinical and pathologic parameters.

CONCLUSIONS

PRKAR1A plays a role in the development of a subset of conjunctival myxomas, particularly in tumors fulfilling stringent morphologic criteria for myxoma. With the exception of PRKAR1A studies, current immunohistochemical panels cannot reliably distinguish between neoplastic conjunctival myxomas and other myxoid lesions, underscoring the importance of morphology in establishing accurate diagnosis.

Evaluation of the osteoclastogenic process associated with RANK / RANK-L / OPG in odontogenic myxomas

BACKGROUND

Odontogenic myxoma (OM) is a benign intraosseous neoplasm that exhibits local aggressiveness and high recurrence rates. Osteoclastogenesis is an important phenomenon in the tumor growth of maxillary neoplasms. RANK (Receptor Activator of Nuclear Factor κappa B) is the signaling receptor of RANK-L (Receptor activator of nuclear factor kappa-Β ligand) that activates the osteoclasts. OPG (osteoprotegerin) is a decoy receptor for RANK-L that inhibits pro-osteoclastogenesis. The RANK / RANKL / OPG system participates in the regulation of osteolytic activity under normal conditions, and its alteration has been associated with greater bone destruction, and also with tumor growth.

OBJECTIVES

To analyze the immunohistochemical expression of OPG, RANK and RANK-L proteins in odontogenic myxomas (OMs) and their relationship with the tumor size.

MATERIAL AND METHODS

Eighteen OMs, 4 small (<3 cm) and 14 large (> 3cm) and 18 dental follicles (DF) that were included as control were studied by means of standard immunohistochemical procedure with RANK, RANKL and OPG antibodies. For the evaluation, 5 fields (40x) of representative areas of OM and DF were selected where the expression of each antibody was determined. Descriptive and comparative statistical analyses were performed with the obtained data.

RESULTS

There are significant differences in the expression of RANK in OM samples as compared to DF (p = 0.022) and among the OMSs and OMLs (p = 0.032). Also a strong association is recognized in the expression of RANK-L and OPG in OM samples.

CONCLUSIONS

Activation of the RANK / RANK-L / OPG triad seems to be involved in the mechanisms of bone balance and destruction, as well as associated with tumor growth in odontogenic myxomas.

Assessment of CD-105 as an Angiogenic Modulator in Odontogenic Myxomas and Dental Follicles

Aim Odontogenic myxoma is a benign intraosseous neoplasm of the jaws, with a locally aggressive behavior and a high recurrence rate. CD-105 is a homodimeric cell membrane glycoprotein and is a component of the TGF-β1 growth factor receptor complex that modulates angiogenesis by regulating the proliferation, differentiation and cellular migration. The aim of this study is to quantify the microvascular density of the odontogenic myxoma based on the expression of CD-105. Materials and Methods The analysis included 18 odontogenic myxoma and 18 dental follicles as controls. A standard immunohistochemical procedure was performed with the CD-105 antibody. Five representative fields (40×) of the odontogenic myxoma and the dental follicles were selected to determine the microvascular density, which was then followed by a descriptive and comparative statistical analysis. Results Dental follicles presented a significantly higher microvascular density compared with odontogenic myxoma (P = .001). The odontogenic myxoma smaller than 3 cm showed a greater microvascular density than those larger than 3 cm in size (P > .05), and the microvascular density was lower in large odontogenic myxomas as compared with the dental follicles (P = .003). Conclusion A weaker expression of CD-105 in odontogenic myxoma might indicate a lower angiogenic activity, suggesting that vascular proliferation has a limited role in the growth mechanisms and in the aggressive behavior of this neoplasm.

Immunolocalization of VEGF-A and orosomucoid-1 in odontogenic myxoma

OBJECTIVE

The aim of the present study was to determine and establish the immunohistochemical distribution of VEGF-A and ORM-1 protein in odontogenic myxomas to suggest a possible function in the biological behavior of odontogenic myxomas.

MATERIALS AND METHODS

A total of 33 odontogenic myxoma cases and three tooth germs were included. Immunohistochemistry was performed to localize VEGF-A and ORM-1 proteins in tumor cells, endothelial cells and extracellular matrix in the odontogenic myxomas. The intratumoral microvessel density (MVD) was determined with CD34 and Factor VIII antibodies.

RESULTS

Immunopositivity was strong in the endothelial cells, which compose various vessels, and in the randomly oriented stellate, spindle-shaped and round tumoral cells with long cytoplasmic processes. More than half of the extracellular matrix lacked expression of VEGF-A. ORM-1 expression was strong in both endothelial cells and tumor cells, and the myxoid extracellular matrix was positive, with moderate or strong immunoexpression in all cases. An important finding of this study was the statistically significant positive correlation between the expression of ORM-1 and VEGF-A in tumor cells (p=0.02).

CONCLUSIONS

The results of this study suggest that the expression of VEGF-A and ORM-1 may be associated with two mechanisms (angiogenesis and tumor structural viscosity) that may influence tumor growth in odontogenic myxoma.

Molecular basis of cardiac myxomas

Cardiac tumors are rare, and of these, primary cardiac tumors are even rarer. Metastatic cardiac tumors are about 100 times more common than the primary tumors. About 90% of primary cardiac tumors are benign, and of these the most common are cardiac myxomas. Approximately 12% of primary cardiac tumors are completely asymptomatic while others present with one or more signs and symptoms of the classical triad of hemodynamic changes due to intracardiac obstruction, embolism and nonspecific constitutional symptoms. Echocardiography is highly sensitive and specific in detecting cardiac tumors. Other helpful investigations are chest X-rays, magnetic resonance imaging and computerized tomography scan. Surgical excision is the treatment of choice for primary cardiac tumors and is usually associated with a good prognosis. This review article will focus on the general features of benign cardiac tumors with an emphasis on cardiac myxomas and their molecular basis.

Primary cardiac myxomas: report of 28 cases and review the literature

PURPOSE

Although primary cardiac tumors are rare, cardiac myxoma is the most common seen intracardiac tumor. This study summarizes our surgical experience with cardiac myxomas.

METHODS

Twenty-eight cases of cardiac myxoma that were surgically treated in our center between January 1990 and March 2010 were retrospectively reviewed. In all patients the New York Heart Association (NYHA) functional classification was used to assess the functional status, and C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) levels were measured before and after surgery.

RESULTS

Nineteen patients were female and 9 male. The mean age was 53.3 ± 12.7 years (range 4-73). The most common symptom was dyspnea (86%). Two patients presented with peripheral embolism. In preoperative assessment of functional status, 24 of the patients were in NYHA Class II, 2 of them were in Class I and the other 2 patients were in Class III. All patients were in NYHA class I in the early postoperative period up to long-term follow up. The mean preoperative CRP and ESR levels were 47.3 ± 14.6 mg/l (range 30-79) and 52.8 ± 21.4 mm/h (range 28-82), respectively. One month after surgery, CRP and ESR levels returned back to normal values. Postoperative CRP and ESR levels were 8.4 ± 2.6 mg/l (range 1-12) and 7.9 ± 4.8 mm/h (range 3-18), respectively.

CONCLUSION

Myxomas should be considered in all patients with embolism. After surgical resection of cardiac myxomas, the functional status of patients improve and CRP and ESR levels become normal.

Ectomesenchymal chondromyxoid tumour of the tongue. A review of histological and immunohistochemical features

BACKGROUND

Ectomesenchymal chondromyxoid tumour (ECT) is a rare, benign neoplasm of uncertain histogenesis, which appears to exclusively involve the oral cavity, particularly the tongue.

CASE REPORT

We report the case of a 27-year-old woman with a 0.7 cm tumoral lesion of 3 months' duration on the dorsum of the tongue. Histologically, it comprised well-circumscribed, unencapsulated lobular proliferations of fusiform and polygonal cells, with varying degrees of cellularity, with neoplastic cells often set in a myxoid, chondroid or hyalinized background. Immunohistochemistry revealed positivity of the neoplastic cells for antibodies directed against S-100, glial fibrillary acidic protein and vimentin, plus negativity for CD-57(leu-7), epithelial membrane antigen, smooth muscle actin, desmin and cytokeratin AE1-AE3. The diagnosis was consistent with ECT. Total excision was performed and there has been no recurrence after 10 months' follow-up.

CONCLUSION

This is the 37th case reported in the English language literature; ECT is characterized microscopically by a biphasic myxoid and chondroid pattern. Immunohistochemical expression of S100, glial fibrillary acidic protein and vimentin, very helpful in confirming diagnosis, suggest a probable mesenchymal and neural origin of this rare entity.

Contribution of monocytes to overproduction of interleukin-6 in a case of cardiac myxoma

Cardiac myxoma cells have been demonstrated to produce interleukin (IL)-6, but its role in the systemic and immunologic manifestations of patients with this tumor is controversial. There is no evidence of any other source of such cytokine, but here we report a case of myxoma with systemic manifestations at diagnosis in which we evaluated the IL-6 production by peripheral blood cells before and after surgical tumor resection. Peripheral blood mononuclear cells were isolated by density gradient centrifugation, and the IL-6 expression in monocytes and lymphocytes was evaluated by flow cytometry. Before surgery, 74.4% of monocytes produced IL-6, but 1 month after surgery, a decrease in both the number of monocytes and the percentage of these cells expressing IL-6 was found along with an improvement of systemic and immunologic manifestations. Here, we demonstrated for the first time that monocytes contribute to the elevated production of IL-6 in patients with myxoma.

Huge Biatrial Primary Cardiac B-cell Lymphoma resulting in Bilateral Atrioventricular Valve Obstruction

We report the case of a 48-year-old man with a clinical syndrome caused by both pulmonary and systemic venous congestion. Echocardiography indicated a huge tumor occupying both dilated atria almost completely, seeming to invade from the atrial septum. A test for HIV was negative. Our primary diagnosis was a biatrial myxoma. Urgent surgery was performed disclosing large cell B-cell primary cardiac lymphoma. The patient died 8 days later. Primary cardiac lymphoma is extremely rare in immunocompetent patients. Its rarity and heterogenous clinical presentation make diagnosis difficult. As tissue characterization is still beyond the capabilities of currently available echocardiography, a combination of examinations are indicated, when the clinical condition is relatively stable, in order to reach the exact diagnosis.

Analysis of GNAS1 and PRKAR1A gene mutations in human cardiac myxomas not associated with multiple endocrine disorders

Cardiac myxomas are rare tumors that usually occur as sporadic lesions or,more rarely, in the familial form,mostly in the context of Carney complex (CNC). The molecular basis for the development of cardiac myxomas is unclear. However, somatic activating mutations in the GNAS1 gene (the gsp oncogene) are detected in the myocardium ofMcCune-Albright syndrome patients while germ-line mutations in the PRKAR1A gene are associated with CNC and familial myxomas. We investigated the presence of activating missense mutations in the GNAS1 gene as well as of inactivating mutations in PRKAR1A in 29 sporadically occurring cardiac myxomas. No gsp and no PRKAR1A mutations were found by direct sequencing of PCR products amplified from tumoral DNA. This is the first study including a large series of sporadic, isolated cardiac myxomas and showing that these cardiac neoplasms do not share the same mutations found in familial forms.

The role of tumor vascularisation in benign and malignant cardiovascular neoplasms: a comparison of cardiac myxoma and sarcomas of the pulmonary artery

Neoangiogenesis is involved in the development and progression of malignant tumors. Vascular endothelial growth factor (VEGF) and its receptors have been designated a central part in this process. Since the significance of the assessment of angiogenesis in soft tissue tumors is still a matter of debate, we investigated the vascularisation of cardiac myxomas and compared it with pulmonary artery sarcomas (PAS). Angiogenesis in 18 PAS and 20 myxomas was assessed by morphometry. An immunohistochemical analysis of growth factors and their receptors, HIF-1alpha and tumor-associated macrophages (TAM) was performed. Results showed that microvessel density (MVD) in PAS was significantly higher at the border of necrosis versus the areas without necrosis but no difference was observed between PAS and myxomas. Vascular surface area (VSA) and intervascular distances showed a higher vascularisation at the border of necrosis compared to myxomas, which was not significant. VEGF expression was higher in PAS compared to myxomas and was prominent at the sites of necrosis. HIF-1alpha expression was marked at the border of necrosis in PAS but was absent in myxomas. Infiltration of the macrophages was significantly higher in myxomas compared to the sarcomas. VEGFR-2 expression was detected in a subset of tumor cells and in blood vessels mainly at the tumor periphery, whereas VEGFR-1 was weakly expressed in the tumors but prominent in the macrophages in cardiac myxomas. PDGF receptors and their ligands are strongly present in myxomas and to a lesser extent in the sarcomas. In conclusion, benign and malignant cardiovascular tumors with a different pathophysiology develop a comparable vascularisation. Hypoxia appears to be the strongest inducer of neoangiogenesis in the sarcomas. The expression of receptor tyrosine kinases of the VEGF family provides a basis for an adjuvant therapy.

Magnetic resonance imaging and spectroscopy of pilomyxoid astrocytomas: case reports and comparison with pilocytic astrocytomas

BACKGROUND AND PURPOSE

Pilomyxoid astrocytomas (PMAs) have been described only recently. They appear as low-grade tumors sharing imaging features similar to pilocytic astrocytomas (PAs). However, pilomyxoid astrocytomas have different histological features and behave more aggressively than PAs. We present the imaging and proton spectroscopic (magnetic resonance spectroscopy; MRS) findings in 3 patients with PMA and compare them with those of PA arising in other sites.

METHODS

Three patients who later proved to harbor PMA were studied with MR imaging and multivolume MRS. We analyzed the imaging findings, with attention to location, size, signal intensities, pattern of enhancement, and edema. In addition, we analyzed the MRS, with attention to the peaks of choline (Cho), creatine (Cr), N-acetyl aspartate, lipids, lactate, and myoinositol, and ratios between these metabolites. We compared the MRS studies of PMA with those of PA located in the hypothalamus and brain stem.

RESULTS

In 2 patients, the PMAs were located in the chiasmatic-hypothalamic and third-ventricular-hypothalamic regions, showing solid enhancement, high T2 signal intensity, and hydrocephalus. One PMA was found in the right parietal lobe showing a well-defined mass without enhancement and high T2 signal intensity. The 2 PMAs showed high Cho/Cr ratios in peritumoral regions at long echo time in comparison with PA. A third PMA showed slight elevation of Cho/Cr ratio in peritumoral regions and no elevation of Cho/Cr ratios within the mass when compared with a PA. Short echo time MRS obtained in 2 PMAs showed low myoinositol/Cr ratios in tumoral regions in comparison with PA.

CONCLUSIONS

Our 2 PMAs showed imaging features similar to those described in the literature. Magnetic resonance spectroscopy showed elevated Cho/Cr outside their enhancing margins, which may be related to their more aggressive behavior when compared with PA. The third PMA was different to those previously reported in the literature because it was hemispheric rather than hypothalamic in location in addition to having low intratumoral ratios of Cho/Cr.

Aggressive Angiomyxoma of the Vulva With a Sole t(5;8)(p15;q22) Chromosome Change

Aggressive angiomyxoma of the vulva is uncommon and the pathogenesis remains unclear. Recently, a few cytogenetic studies demonstrated chromosomal abnormalities in aggressive angiomyxoma of the vulva. A 45-year-old Japanese woman complaining of right-side vulva tumor measuring 3 cm in diameter was referred to our hospital. The mass was located at the right side of the rectovaginal septum and was closely adherent to the rectal serosa and the levator muscle ani. The tumor was completely resected. A pathological examination demonstrated aggressive angiomyxoma of the vulva. Chromosomal analysis of the tumor demonstrated a sole t(5;8)(p15;q22) translocation. This is the first case of an aggressive angiomyxoma of the vulva with a sole t(5;8)(p15;q22) translocation.

Role of matrix metalloproteinases and their tissue inhibitor of metalloproteinases in myxomatous change of cardiac floppy valves

To clarify the underlying cause of myxomatous changes in cardiac floppy valves, the expression of the matrix metalloproteinases (MMP) and the tissue inhibitors of metalloproteinases (TIMP) was investigated in cardiac valves. Valves were obtained from nine patients with floppy valves, from 13 patients with other valvular disease types, and from four patients with normal valves. Immunohistochemical analyses for MMP-2, MMP-9, TIMP-1, and TIMP-2, and gelatin zymography for MMP-2 and MMP-9 were performed. Compared with the spongiosa of normal valves, the myxomatous area of floppy valves had stronger immunohistochemical reaction to MMP-2 and MMP-9, and weaker reaction to TIMP-2. Activated MMP-2 and MMP-9 were detected in eight out of nine cases of floppy valves. Activated MMP-2 was detected at low levels in two cases of normal valves showing mild expansion of the spongiosa without macroscopic floppiness. The ratio of active/total MMP-2 and MMP-9 increased in floppy valves compared with normal valves. These results suggest that the imbalance between MMP and TIMP and the increased activity of MMP-2 and MMP-9 may correlate with myxomatous changes observed in floppy valves. Valves with a slight myxomatous change and activated MMP-2 may develop into floppy valves with increases in the activity of MMP.

[Clinicopathologic features of cardiac myxoma--a report of 47 cases]

BACKGROUND & OBJECTIVE

Myxoma is the most common neoplasm of the heart, and has various morphologic structures, but its biological behaviors and histogenesis are still controversial. This study was to summarize the clinical, histomorphologic, and immunophenotypic features of cardiac myxoma.

METHODS

The clinical data and HE sections of 47 cases of cardiac myxoma were reviewed. Special staining and immunohistochemical staining for 10 kinds of antibodies were carried on some cases to observe the morphologic features.

RESULTS

Of the 47 patients with cardiac myxoma, 32 were women, the youngest was 3 years old. The volume of tumors ranged from 0.7 cm x 0.7 cm x 0.4 cm to 12 cm x 8 cm x 7 cm. Of the 47 tumors, 42 were pedunculated, the rest had broad fundus without pedicel; 43 located in the left atrium, 3 in the right atrium, and 1 in the left ventricle where near to the apex of heart. Tumor cells were stellate, spindle, round, or irregular, and arranged as masses or stripes, with abundant mucus around them. Tumor cells surrounded arterioles in 4 cases. Pseudo-capsule was formed by hyperplastic fibrous tissue in 4 cases. The mesenchyma presented angiomatous fashion in 2 cases. Sheets of old hemorrhage, hemosiderin and iron salt deposition, and fibrosis were observed in 7 cases. One case had foci adenoid structure, 1 lipoid metaplasia and ossification, 1 was rich of cells. Vimentin and CD34 were found in lining cells and parenchymal cells in 12 cases. Cytokine kinase (CK) and epithelial membrane antigen (EMA) were positive in the region of adenoid differentiation. Proliferating cell nuclear antigen (PCNA) and Ki67 were positive in the cell-rich tumor. None of the 21 patients had tumor recurred after follow-up.

CONCLUSIONS

Cardiac myxoma has various secondary morphologic changes, including adenoid metaplasia, old hemorrhage, fibrosis, ossification, and lipoid metaplasia. Whether the cell-rich tumors tend to be malignant needs further study. Cardiac myxoma may come from multipotential mesenchymal cells.

Human degenerative valve disease is associated with up-regulation of low-density lipoprotein receptor-related protein 5 receptor-mediated bone formation

OBJECTIVES

The goal of this research was to define the cellular mechanisms involved in myxomatous mitral valve disease and calcific aortic valve disease and to redefine the term degenerative valve disease in terms of an active cellular biology.

BACKGROUND

"Degenerative" valvular heart disease is the primary cause of regurgitant and stenotic valvular lesion in the U.S. However, the signaling pathways are not known. We hypothesize that valve degeneration occurs due to an osteoblastic differentiation process mediated by the low-density lipoprotein receptor-related protein 5 (Lrp5) signaling pathway to cause valve thickening.

METHODS

We examined human diseased valves: myxomatous mitral valves (n = 23), calcified tricuspid aortic valves (n = 27), calcified bicuspid aortic valves (n = 23), and control tissue from mitral and aortic valves (n = 40). The valves were examined by reverse transcriptase-polymerase chain reaction, Western blot, and immunohistochemistry for signaling markers important in osteoblast differentiation: Sox9 and Cbfa1 (transcription factors for osteoblast differentiation); Lrp5 and Wnt3 (osteoblast differentiation signaling marker), osteopontin and osteocalcin (osteoblast endochrondral bone matrix proteins), and proliferating cell nuclear antigen (a marker of cell proliferation). Cartilage development and bone formation was measured by Alcian blue stain and Alizarin red stain. Computed Scano MicroCT-40 (Bassersdorf, Switzerland) analysis measured calcium burden.

RESULTS

Low-density lipoprotein receptor-related protein 5, osteocalcin, and other osteochrondrogenic differentiation markers were increased in the calcified aortic valves by protein and gene expression (p > 0.001). Sox9, Lrp5 receptor, and osteocalcin were increased in myxomatous mitral valves by protein and gene expression (p > 0.001). MicroCT was positive in the calcified aortic valves and negative in the myxomatous mitral valves.

CONCLUSIONS

The mechanism of valvular heart disease involves an endochondral bone process that is expressed as cartilage in the mitral valves and bone in the aortic valves. Up-regulation of the Lrp5 pathway may play a role in the mechanism for valvular heart disease.

Aggressive angiomyxoma of the vulva: Dramatic response to gonadotropin-releasing hormone agonist therapy

BACKGROUND

Aggressive angiomyxoma (AA) is a vulvovaginal mesenchymal neoplasm with a marked tendency to local recurrence but which usually does not metastasise. Most cases exhibit positive immunohistochemical staining with oestrogen receptor (ER) and, or, progesterone receptor (PR).

CASE

We report a case of AA which exhibited positive immunohistochemical staining with ER and in which radiological examination following resection showed extensive residual tumour. The patient was commenced on gonadotropin-releasing hormone (GnRH) agonist therapy which resulted in complete radiological remission with replacement by scar tissue. The patient is currently maintained on a GnRH agonist.

CONCLUSION

The present case, together with several others reported in the literature, suggests that GnRH agonists may be of value in managing cases of AA, either primary or recurrent, which are not amenable to surgical excision. These agents may also be used to effect a reduction in size, so that more conservative surgery can be undertaken.

Preliminary report of expression of bax in oral cavity pathologies

Bax is considered one of major effectors of apoptosis--programmed cell death. Immunohistochemical analysis of in vitro patterns of bax expression was mostly investigated in mammalian cell lines and tissues. The present study is the first in vivo molecular analysis of bax expression in oral cavity pathologies. The study population consisted of 45 patients with hyperplasia, neoplasm in situ malignancy, and carcinoma. Biopsies were taken from incision line, tumour section, and healthy tissue. bax expression was investigated depending on the site of biopsy material sampling and final histopathology result. No statistically significant difference was demonstrated in bax expression between four hyperplasia subgroups. However, statistically significant differences in bax expression were found between the three basic study groups (P = 0.001). Statistically significant differences in bax expression were demonstrated depending on tissue collection site (P = 0.0002). We conclude that differences in bax expression may play a role in the pathogenesis of neoplastic disease.

Molecular and immunohistochemical investigation of protein kinase a regulatory subunit type 1A (PRKAR1A) in odontogenic myxomas

Odontogenic myxomas are rare benign neoplasms affecting the jaw. Myxomas of bones and other sites occur as part of Carney complex (CNC), a multiple neoplasia syndrome caused by mutations in the PRKAR1A gene, which codes for the regulatory subunit of protein kinase A (PKA). In the present study, 17 odontogenic myxomas from patients without CNC were screened for PRKAR1A mutations and PRKAR1A protein expression by immunohistochemistry (IHC). Mutations of the coding region of the PRKAR1A gene were identified in 2 tumors; both these lesions showed no or significantly decreased immunostaining of PRKAR1A in the tumor compared to that in the surrounding normal tissue. One mutation (c.725C>A) led to a nonconservative amino acid substitution in a highly conserved area of the gene (A213D); the other was a single base-pair deletion that led to a frameshift (del774C) and a stop codon 11 amino acids downstream of the mutation site; both tumors were heterozygous for the respective mutations. Of the remaining tumors, 7 of the 15 without mutations showed almost no PRKAR1A in the tumor cells, whereas IHC showed that the protein was abundant in nontumorous cells. We concluded that PRKAR1A may be involved by its down-regulation in the pathogenesis of odontogenic myxomas caused by mutations and/or other genetic mechanisms. Of the sporadic, nonfamilial tumors associated with PRKAR1A mutations, the odontogenic type was the first myxomatous lesion found to harbor somatic PRKAR1A sequence changes.

Thymoma Arising Within Cardiac Myxoma

Hematopoietic, glandular, and mesenchymal elements can be found within cardiac myxomas; ectopic endocrine tissues and "thymic rests" have also rarely been described. Atrial tumors (one right and one left) from 2 patients (a 69-year-old man and a 77-year-old woman) were encountered among the atrial myxoma cases in one of the author's consultation files. Both tumors were comprised of classic cardiac myxoma (with characteristic rings and syncytial chains of myxoma cells in a loose myxoid matrix) and cellular thymoma-like elements (characterized by a lobulated sheet-like growth of epithelioid spindle cells admixed with small lymphocytes punctuated by vessels with prominent perivascular spaces). Neither patient had evidence of thymoma elsewhere. Immunophenotypically, the thymoma-like component reacted strongly with antibodies to keratins (AE1/AE3, Cam 5.2, wide spectrum, CK19, CK7) and CD57 and weakly with antibodies to CD31, CD34, and calretinin. This intermediate phenotypic expression of both epithelial and vascular antigens likely reflects the multipotential nature of the cells comprising this lesion. The most likely explanation for this extremely unusual finding is neoplastic transformation of thymic rests within a myxoma.

CD34+ fibrocytes in normal mitral valves and myxomatous mitral valve degeneration

We investigated a total of 15 mitral valves with myxomatous degeneration and compared these with normal mitral valves. In normal mitral valves, stromal cells located in the fibrosa and spongiosa showed small bipolar cytoplasmic processes and were found to be positive for CD34, suggesting a close relationship to CD34+ fibrocytes. In cases of myxomatous degeneration, stromal cells showed an altered morphology in that they exhibited multipolar cytoplasmic processes, appeared to be hyperplastic, and were increased in number. This study is the first to report on CD34+ fibrocytes making up the majority of mitral valve stromal cells. Major factors in the development of myxomatous valve degeneration are MMP-9, as well as collagen I and III, which have been reported to be secreted by CD34+ fibrocytes. Therefore, it is likely that CD34+ fibrocytes are involved in the pathogenesis of myxomatous mitral valve degeneration.

A case of vulvar superficial angiomyxoma with necrotizing angiitis-like lesions and expression of granulocyte-colony stimulating factor

A vulvar tumor of 3-year-old girl was resected. The tumor had a pedunculated polypoid appearance with a multinodular surface and was covered by normal colored skin. Histologically, the tumor was lobulated and consisted of sparse stellate- or spindle-shaped tumor cells with a large amount of edematous stroma admixed with myxomatous areas. The tumor was rich in blood vessels of various sizes. Several blood vessels showed fibrinoid necrosis. There was a diffuse neutrophilic infiltration in the stroma. The tumor was diagnosed as a superficial angiomyxoma. Immunohistochemically, the tumor cells diffusely expressed vimentin, focally alpha-smooth muscle actin and desmin. Both estrogen and progesterone receptors were negative. Occasionally, they expressed CD34. Most of the tumor cells expressed granulocyte-colony stimulating factor (G-CSF). Endothelial cells of tumor blood vessels occasionally expressed intercellular adhesion molecule-1 or E-selectin. Some endothelial cells in the tumor were immunolabeled by anti-vascular endothelial growth factor (VEGF) antibody along their luminal surfaces. In the present case, G-CSF and adhesion molecules to neutrophils may have played some roles in neutrophilic infiltration into the tumor and in fibrinoid necrosis of the blood vessels. In addition to these molecules, VEGF may have contributed to vascular growth, leading to edematous stroma.

Increased expression and activity of matrix metalloproteinases characterize embolic cardiac myxomas

Tumor embolism occurs in 30 to 50% of all cases of cardiac myxoma, but the causes are still uncertain. Matrix metalloproteinases (MMPs) are proteolytic enzymes that degrade the extracellular matrix (ECM) and play a crucial role in plaque instability and aortic aneurysm development, in addition to cancer and heart failure. To determine whether MMP activity contributes to tumor embolism, we examined 27 left atrium-sided myxomas, 10 of which showed clinical signs of peripheral embolism. Immunohistochemistry (in all cases) and Western blotting, and in situ and in-gel zymography (in four embolic and six nonembolic consecutive tumors) demonstrated higher expression and activity of MT1-MMP, pro-MMP-2, and pro-MMP-9 in embolic myxomas, whereas pro-MMP-1, MMP-3, and TIMP-1 levels were similar to those of nonembolic tumors. Reverse transcriptase-polymerase chain reaction demonstrated that increased MMP activity was due, at least in part, to increased transcription and that TIMP-2 transcripts increased in embolic myxomas. In vitro, embolic tumor cells retained higher MT1-MMP and pro-MMP-2 levels in basal conditions and after stimulation with interleukin-1beta and interleukin-6. Increased MMP synthesis and release correlated with enhanced ECM degradation products containing glycosaminoglycan chains in embolic myxoma tissue. Our results strongly suggest that MMP overexpression may contribute to an excessive degradation of tumor ECM and increase the risk of embolism in cardiac myxomas.

A Japanese case of familial cardiac myxoma associated with a mutation of the PRKAR1alpha gene

Familial cardiac myxoma is inherited as an autosomal dominant syndrome. Here, we report a Japanese case of familial cardiac myxoma identified as a genetic abnormality. The mother experienced multiple recurrence of tumors in the left atrium and left ventricle 40 months after surgical resection of a left atrial myxoma. All recurrent tumors were successfully resected. Her daughter also had a solitary myxoma in the left atrium, but she had no recurrence after the operation. Both patients had lentigines in their face but no endocrine abnormality. Molecular genetic analysis demonstrated involvement of a mutation in the PRKAR1alpha gene.

Cystic Tumor in the Left Atrium: An Unusual Aspect of a Myxoma

Most cardiac tumors are benign, whereas up to 50 % of the diagnosed cases are histologically myxomas. The common clinical signs are rhythm disturbances, myocardial ischemia, pulmonary edema, syncope and cardiac arrest. They do normally lead to the diagnostic hypothesis of an intracardiac mass. The primary modality for imaging is echocardiography which usually confirms the suspected diagnosis. But in rare cases there are masses which cannot be exactly identified by this technique. Here we present a patient with an atypical echocardiography of an unusual intracardiac tumor.

Gene expression analysis to identify mRNA markers of cardiac myxoma

cDNA expression arrays were used to identify mRNA expression markers for cardiac myxoma. The RNA profile analysis suggests that cardiac myxoma should be considered as a stand-alone tissue rather than a pathological modification of particular normal tissue. The analysis reveals a set of genes which are highly and steadily expressed in cardiac myxomas and can serve as an mRNA expression markers of the tumour. Marker status of selected genes was confirmed by reverse transcriptase polymerase chain reaction analysis. Genes MIA (melanoma inhibitory activity) and PLA2G2A (phospholipase A2, group IIA) show the highest specificity as cardiac myxoma markers, since they have more than 10-fold higher RNA level in cardiac myxomas than in any one of 15 normal tissues tested. Among markers of myxoma at least three are participants of phospholipid metabolism: ANXA3, PLA2G2A, and phospholipid transfer protein. Tissue inhibitor of metalloproteinase 1 and secretory leucocyte protease inhibitor are inhibitors of proteases degrading extracellular matrix proteins and participating in cell proliferation regulation. MIA, SPP1, fibromodulin are modulators or participants of the interaction between extracellular matrix proteins and their cell surface receptors. SOX9 is a transcription factor required for chondrocyte differentiation. Calretenin (CALB2) is an intracellular calcium-binding protein with poorly understood function.

Cardiac myxoma of the tricuspid valve in a dog

A case of cardiac myxoma arising from the tricuspid valve is described in an 8-year-old dog that had suffered intermittent episodes of syncope. At surgical operation, a large, irregular, gelatinous mass was found attached to the septal leaflet of the tricuspid valve. The excised tumour, measuring 5x4x3.5 cm, had a grey-to-yellow, friable, mucoid, multilobulated and polypoid appearance, with focal haemorrhage. Histologically, the tumour consisted of a hypocellular mass of a myxoid matrix, rich in acid mucopolysaccharides, with a supporting structure of spindle-like, elongated or stellate cells scattered in an abundant stroma. The surface of the mass was covered by a single layer of endothelial-like cells. Immunohistochemistry revealed that the surface cells of the mass were positive for the endothelial marker CD34 and the constituent cells within the mass reacted positively and uniformly with antibodies to vimentin and alpha-smooth muscle actin. The dog died 36 h after the operation and, at necropsy, wide dissemination of myxomatous embolization to the intrapulmonary arteries was found.

Aggressive angiomyxoma in the scrotum expressing androgen and progesterone receptors

Aggressive angiomyxoma is a rare benign mesenchymal myxoid tumor that arises from the pelvic soft tissues and perineum in relatively young females. This tumor has the ability to infiltrate locally and has a high risk of local recurrence after extirpation, but no potential to metastasize. We report here a rare case of aggressive angiomyxoma that developed in the scrotum of a 47-year-old male. Immunostaining of the resected specimen revealed that the tumor cell nuclei stained strongly and diffusely for androgen receptors (80% of the tumor cells), and moderately and partly for progesterone receptors (20% of the tumor cells). However, staining was negative for estrogen receptors. It is highly suggested that the growth of aggressive angiomyxoma in males may depend on androgen manipulation, contrary to its frequent and close association with estrogen receptor expression, which has been reported in females.

Mucin gene expression in cardiac myxoma

Myxoma is the most common benign neoplasm of the heart. This work is the first to present an unusual left atrium and mitral valve cardiac myxoma which cannot be completely resected. This cardiac myxoma was also associated with abundant mucopolysaccharidic matrix, including mucin. Mucin gene expression is cell- and tissue-specific, with variations during cell differentiation and inflammation, and is altered during carcinogenesis. The expression of mucin genes in cardiac myxoma has never been elucidated previously. Detailed immunohistochemical analysis of MUC1, MUC2 and MUC5AC has been performed in this left atrium and mitral valve myxoma. Notably, the expressions of mucins in cardiac myxoma must be further evaluated.

Minichromosome maintenance protein in myxofibrosarcoma

Histopathological assessment of myxofibrosarcoma may be difficult, especially on the basis of a small core biopsy, which enables only a crude evaluation of grade and prognosis. We have tested the hypothesis that determination of cell cycle state may assist in the diagnostic assessment of myxofibrosarcoma. We have studied 51 cases of high-grade (n=20), intermediate-grade (n=21), and low-grade (n=10) myxofibrosarcomas, as well as nine cases of benign myxoma. Cell cycle state within tumors was determined by immunostaining for the recently described marker minichromosome maintenance protein 2 (MCM2), together with Ki67. Labelling indices for both markers were correlated with tumor grade, mitotic index, and time to first recurrence. The MCM2 labelling indices were significantly higher than the Ki-67 labelling indices. Both indices showed a significant correlation with the mitotic index and both showed significant increases with increasing grade of myxofibrosarcoma. The MCM2 labelling index (but not the Ki67 labelling index) showed a significant inverse exponential correlation with the time to first recurrence. Myxoid and cellular areas showed no difference in the MCM2 and Ki-67 labeling index, suggesting that clinically useful information could be obtained from any component of a myxofibrosarcoma sampled in a needle biopsy and/or cytological specimen. We therefore suggest that assessment of cell cycle state may be a useful diagnostic adjunct in the histopathological assessment of myxofibrosarcoma, by enabling more accurate determination of grade and prediction of outcome.

The expression of apoptotic proteins and matrix metalloproteinases in odontogenic myxomas

PURPOSE

The odontogenic myxoma is a rare benign tumor affecting the jaws. We hypothesize that odontogenic myxomas have dysregulated antiapoptotic mechanisms to assist in neoplastic growth. We believe that antiapoptotic proteins of the Bcl-2 family are over expressed and that tumor cells must generate some form of matrix proteinase. The aim of this study was to evaluate odontogenic myxomas for the expression of cell cycle protein Ki-67, apoptosis-regulating proteins Bcl-2, Bcl-XL, Bak, and Bax, and matrix metalloproteinases MMP-2, MMP-3, and MMP-9.

MATERIALS AND METHODS

Odontogenic myxomas submitted to oral pathology between 1974 and 1998 were evaluated. Twenty-six paraffin-embedded tissue sections were used in a standard immunohistochemistry protocol and incubated with one of the following antibodies: Bcl-2, Bcl-XL, Bak, Bax, or Ki-67. The sections were then incubated with anti-immunoglobulin conjugated to peroxidase-labeled dextran polymer in a Tris-HCl buffer. Counts of positive (staining) cells were completed in 5 high-power fields for each specimen. Each slide was reviewed by 2 investigators, and final data were pooled and averaged.

RESULTS

Specimen slides showed an increase in cells staining positively for anti-apoptotic proteins Bcl-2 and Bcl-X. An average of 6.5% of specimen cells were positive for Bcl-2 and 10.4% for Bcl-X. Control tissue showed only 1.1% of cells to be positive for Bcl-2 and 1.2% for Bcl-X. Less than 1% of both specimen and control cells stained positively for Ki-67. Proapoptotic proteins (Bak and Bax) were not detected in tumor cells. Ninety percent of tumor cells stained positively for MMP-2 compared with 10% of controls. Specimen and controls were negative for MMP-3 and MMP-9.

CONCLUSION

Odontogenic myxoma tumor cells did not show an increase in cell division. Less than 1% of tumor and control cells were positive for Ki-67. Odontogenic myxoma tumor cells showed increased expression of antiapoptotic proteins (Bcl-2 and Bcl-X) and the matrix metalloproteinase MMP-2. This study suggests that 2 mechanisms of disease progression used by the odontogenic myxoma are the production of antiapoptotic proteins and the secretion of matrix metalloproteinases.

Herpes simplex virus type 1 infection associated with atrial myxoma

Some findings suggest an infectious factor in cardiac myxoma and certain histopathological features indicate herpes simplex virus type 1 (HSV-1) infection. We hypothesized that HSV-1 may be involved in the pathogenesis of cardiac myxoma. Paraffin-embedded tissue samples from 17 patients with atrial myxoma were investigated for HSV-1 antigen by immunohistochemistry and viral genomic DNA by nested polymerase chain reaction. The histogenesis and oncogenesis of atrial myxoma were assessed by the expression of calretinin, Ki67, and p53 protein, respectively. Autopsy myocardial samples, including endocardium from 12 patients who died by accident or other conditions, were used for comparison. HSV-1 antigen was detected in atrial myxoma from 12 of 17 patients: 8 of these 12 samples were positive also for HSV-1 DNA. No HSV-1 antigen or DNA was found in tissue from the comparison group. Antigens of HSV-2, varicella-zoster virus, Epstein-Barr virus, and cytomegalovirus were not found in atrial myxoma. Calretinin was found in myxoma cells of all 17 cases but Ki67 was present only in smooth muscle cells or infiltrating cells in some cases. p53 was not detectable in any myxoma. Most infiltrating cells were cytotoxic T lymphocytes. These data suggest that HSV-1 infection is associated with some cases of sporadic atrial myxoma and that these may result from a chronic inflammatory lesion of endocardium.

Production of Endothelin-1 and Big Endothelin-1 by Human Cardiac Myxoma Cells-Implications for the Origin of Myxomas-

BACKGROUND

Although the origin of cardiac myxomas is still controversial, the 2 main hypotheses are that the tumor cells originate either from multipotential mesenchymal cells or from endocardial neural tissue.

METHODS AND RESULTS

The production of various cytokines in 2 human cardiac myxoma cell lines was examined by enzyme-linked immunosorbent assay. After 7 days of culture, extremely high concentrations of interleukin-6 were detected in the culture media from both myxoma cell lines. Increased production of CXC chemokines, interleukin-8 and growth-related oncogene-alpha, were observed in both myxoma cell lines. Endothelin (ET)-1 and its precursor, big ET-1, were detected in the culture media from both myxoma cell lines. The production of both ET-1 and big ET-1 by myxoma cells was higher than by human umbilical vein endothelial cells. Similar to endothelial cells, myxoma cells did not produce stem cell factor, granulocyte colony-stimulating factor, hepatocyte growth factor, or ET-3.

CONCLUSIONS

The similarity of the cytokine production pattern between cardiac myxoma cells and endothelial cells supports the hypothesis that the tumor cells originate from mesenchymal cells capable of endothelial differentiation. Overproduction of CXC chemokines may explain, in part, the malignant potential of histologically benign myxomas.

Vascular Endothelial Growth Factor is an Autocrine Growth Factor for Cardiac Myxoma Cells

BACKGROUND

Cardiac myxomas are generally considered benign, but malignant tumors have been reported. Vascular endothelial growth factor (VEGF), an angiogenic factor, plays a role in the growth, progression, and metastasis of solid tumors and it has been reported that VEGF expression is upregulated in cardiac myxomas that have a high microvessel density. The purpose of this study was to determine whether cardiac myxoma cells possess a VEGF-autocrine system that regulates tumor growth.

METHODS AND RESULTS

Immunohistochemical analyses revealed the presence of VEGF and its receptors, VEGFR-1 (flt-1) and VEGFR-2 (KDR/flk-1), in the cytoplasm of tumor cells from 18 of 18 myxoma tissue specimens examined. Two different myxoma cell lines were established and constitutively secreted large amounts of VEGF as determined by enzyme-linked immunosorbent assay. The expression of VEGF, VEGFR-1, and VEGFR-2 mRNA was detected in both cell lines by reverse-transcriptase polymerase chain reaction. Myxoma cell proliferation, as determined by thymidine incorporation, was enhanced by the addition of VEGF in a dose-dependent manner, and cell proliferation was inhibited in a dose-dependent manner by the addition of a neutralizing VEGF antibody.

CONCLUSIONS

These results indicate that cardiac myxoma cells possess a VEGF-autocrine system, which could contribute to the malignant potential of histologically benign myxomas through direct stimulation of tumor cell growth as well as through induction of angiogenesis.