Characterization of malignant thrombus in an invasive thymoma with intravascular growth

We report an unusual case of an invasive thymoma with a thrombus in the right atrium and describe the radiological findings consistent with the malignant nature of the thrombus. The thrombus showed significant enhancement on computerized tomography images similar to the tumoral mass. On magnetic resonance imaging, both the tumor and the thrombus have heterogeneously high signal intensities on T2-weighted images. On diffusion-weighted images they both exhibit high signal intensity and low apparent diffusion coefficient (ADC) values which support the malignant nature of the thrombus and the mass.

[Correlation of CKP and VEGF expression and microvessel density to spiral CT manifestations of thymoma]

OBJECTIVE

To investigate the correlation of cytokeratin pan (CKP), vascular endothelial growth factor (VEGF) expression and microvessel density (MVD) to spiral CT manifestations of thymoma.

METHODS

Eighty-four thymoma patients were underwent spiral CT examination, and 40 of the patients also had enhanced CT examination. All the CT findings were carefully reviewed to analyze their correlation to the expressions of CKP, VEGF and MVD.

RESULTS

The enhancement on spiral CT images increased with the levels of VEGF expression and MVD counting (P<0.01). Significant correlations were observed between VEGF expression, MVD counting and such spiral CT findings as lobular contours, cusp-like or sawtooth-like margins and tumor invasions of the pleural membrane, pericardium and great vessels (P<0.05). CKP expression showed no obvious correlation to these findings by spiral CT.

CONCLUSION

Spiral CT can reflect the pathological characteristics of thymoma, and may serve as a noninvasive modality for preoperative evaluation of thymoma.

Angiogenesis in the human thymoma assessed by subclassification of tumor-associated blood vessels and endothelial cells proliferation

The prognostic value of tumor-associated angiogenesis is still a subject of debate. As microvascular density and the expression of different growth factors were not demonstrated to be good predictors of the response to antiangiogenic and antivascular therapy, there is a strong need to search for more sensitive markers. In the present study we evaluated by double immunohistochemical staining the profile of tumor-associated blood vessels and the rate of endothelial cell proliferation in patients with thymoma (n=38). Results were compared with specimens of normal thymus and from patients with myasthenia gravis. We found a significant increase in the number of immature and intermediate blood vessels in the tumor area of thymoma, regardless the histological type of the tumor. Proliferating endothelial cells were found in 15 cases, and co-expression of Ki67 and CD34 had the highest value in immature vessels. Both blood vessel type and endothelial cell proliferation significantly correlated with invasive thymoma. Based on these findings, it can be assumed that the type of tumor-associated vessel together with endothelial cell proliferation are useful predictors of invasion, immature and intermediate vessels can be targeted with antivascular drugs and endothelial cell proliferation could be used as a good predictor of the response to antiangiogenic therapy.

Increased mast cell density and microvessel density in the thymus of patients with myasthenia gravis

There were investigated 15 cases with normal thymus removed during cardiac surgery and nine cases with clinical signs of myasthenia gravis. Four patients with myasthenia gravis had thymoma (three invasive, one non-invasive). Specimens were fixed in buffer formalin, embedded in paraffin and slides were stained with Hematoxylin-Eosin and Alcian blue-Safranin. Additional slides were stained for factor VIII in order to estimate microvessel density. Mast cell density was performed at magnification x400, and microvessel density at magnification x200, using the "hot spot" method. There were found intralobular mast cells in all cases, located mainly in the cortex (6.53 in the normal thymus, 21.4 in patients with myasthenia gravis, and 10 in thymoma-associated myasthenia gravis). A significant increase in the number of intralobular mast cells was noticed in patients with myasthenia gravis without thymoma (p < 0.001), and a moderate increase in patients with thymoma-associated myasthenia gravis (p < 0.023). Values of microvessel density were 10.3 for the normal thymus, 33 for myasthenia gravis without thymoma and 21.8 for myasthenia gravis with associated thymoma. A strong correlation was found between the number of mast cells and microvessel densities in all three conditions.

Acute Presentation of Thymoma With Infarction or Hemorrhage

The presentation of thymomas is variable; most are asymptomatic and others present with local compression symptoms or a parathymic syndrome. Rarely thymomas present as an acute emergency with severe chest pain from either infarction or hemorrhage of the tumor. This rare presentation usually leads the clinician initially away from the diagnosis of thymoma. We present 4 patients who presented with infarction (3 patients) and hemorrhage (1 patient) who were initially believed to have a lymphoma. Preoperative biopsies were unrevealing. All had a complete resection and were in the early Masaoka stage. There have been no recurrences in follow-up. The astute clinician should be aware of this unusual presentation. The prognosis seems to be good in patients who present with infarction or hemorrhage.

The LIM-domain protein Lmo2 is a key regulator of tumour angiogenesis: a new anti-angiogenesis drug target

The growth of solid tumours requires a blood supply provided by re-modeling of existing blood vessel endothelium (angiogenesis). Little is known about transcription regulators which are specific for the control of tumour angiogenesis. The proto-oncogene LMO2 encodes a LIM domain transcription regulator which controls angiogenesis during mouse embryogenesis where it regulates remodelling of the capillary network into mature vessels. We now show that Lmo2 expression is augmented in tumour endothelium such as mouse thymomas and human lung tumours. The functional significance of this Lmo2 expression was assessed in teratocarcinomas induced in nude mice by subcutaneous implantation of Lmo2-lacZ targeted ES cells. CD31-positive, sprouting endothelium of ES-cell origin occurred in teratocarcinomas from heterozygous Lmo2-lacZ ES cells but none occurred from null Lmo2-lacZ ES cells. Therefore, in this model Lmo2 is an obligatory regulator of neo-vascularization of tumours. These data suggest that LMO2 function may be a drug target in cancer and other conditions characterized by neo-vascularization.

Angiostatin enhances B7.1-mediated cancer immunotherapy independently of effects on vascular endothelial growth factor expression

Tumors must develop an adequate vascular network to meet their increasing demands for nutrition and oxygen. Angiostatin, a multiple kringle (1-4)-containing fragment of plasminogen, is an effective natural inhibitor of tumor angiogenesis. Here we show that gene transfer of angiostatin into small (0.1 cm in diameter) solid EL-4 lymphomas established in syngeneic C57BL/6 mice led to reduced tumor angiogenesis and weak inhibition of tumor growth. In contrast, when angiostatin gene therapy was preceded by in situ gene transfer of the T-cell costimulator B7.1, large (0.4 cm in diameter) tumors were rapidly and completely eradicated, whereas B7.1 and angiostatin monotherapies were ineffective. Combined gene transfer of B7.1 and angiostatin generated potent systemic antitumor immunity that was effective in eradicating a systemic challenge of 10(7) EL-4 cells. Gene transfer of angiostatin expression plasmids led to overexpression of angiostatin in tumors, increased apoptosis of tumor cells, and decreased density of tumor blood vessels, which may allow the immune system to overcome tumor immune resistance. The latter effects were not the result of a decrease in vascular endothelial growth factor expression, as tumoral vascular endothelial growth factor expression increased slightly after angiostatin gene transfer, presumably in response to increasing hypoxia. These results suggest that combining immunogene therapy with a vascular attack by angiostatin is a particularly effective approach for eliciting antitumor immunity.

Vascular attack by 5,6-dimethylxanthenone-4-acetic acid combined with B7.1 (CD80)-mediated immunotherapy overcomes immune resistance and leads to the eradication of large tumors and multiple tumor foci

The promise of cancer immunotherapy is that it will not only eradicate primary tumors but will generate systemic antitumor immunity capable of destroying distant metastases. A major problem that must first be surmounted relates to the immune resistance of large tumors. Here we reveal that immune resistance can be overcome by combining immunotherapy with a concerted attack on the tumor vasculature. The functionally related antitumor drugs 5,6-dimethylxanthenone-4-acetic acid (DMXAA) and flavone acetic acid (FAA), which cause tumor vasculature collapse and tumor necrosis, were used to attack the tumor vasculature, whereas the T-cell costimulator B7.1 (CD80), which costimulates T-cell proliferation via the CD28 pathway, was used to stimulate antitumor immunity. The injection of cDNA (60-180 microg) encoding B7.1 into large EL-4 tumors (0.8 cm in diameter) established in C57BL/6 mice, followed 24 h later by i.p. administration of either DMXAA (25 mg/kg) or FAA (300 mg/kg), resulted in complete tumor eradication within 2-6 weeks. In contrast, monotherapies were ineffective. Both vascular attack and B7.1 immunotherapy led to up-regulation of heat shock protein 70 on stressed and dying tumor cells, potentially augmenting immunotherapy. Remarkably, large tumors took on the appearance of a wound that rapidly ameliorated, leaving perfectly healed skin. Combined therapy was mediated by CD8+ T cells and natural killer cells, accompanied by heightened and prolonged antitumor cytolytic activity (P < 0.001), and by a marked increase in tumor cell apoptosis. Cured animals completely rejected a challenge of 1 x 10(7) parental EL-4 tumor cells but not a challenge of 1 x 10(4) Lewis lung carcinoma cells, demonstrating that antitumor immunity was tumor specific. Adoptive transfer of 2 x 10(8) splenocytes from treated mice into recipients bearing established (0.8 cm in diameter) tumors resulted in rapid and complete tumor rejection within 3 weeks. Although DMXAA and B7.1 monotherapies are complicated by a narrow range of effective doses, combined therapy was less dosage dependent. Thus, a broad range of amounts of B7.1 cDNA were effective in combination with 25 mg/kg DMXAA. In contrast, DMXAA, which has a very narrow range of high active doses, was effective at a low dose (18 mg/kg) when administered with a large amount (180 microg) of B7.1 cDNA. Importantly, combinational therapy generated heightened antitumor immunity, such that gene transfer of B7.1 into one tumor, followed by systemic DMXAA treatment, led to the complete rejection of multiple untreated tumor nodules established in the opposing flank. These findings have important implications for the future direction and utility of cancer immunotherapies aimed at harnessing patients' immune responses to their own tumors.

[Intravascular invasion of a thymoma from the thymic vein to the right atrium--a case report]

A 43-year-old woman with a complaint of facial swelling was admitted to our hospital. A chest roentgenogram revealed a mass in the mediastinum. Chest CT and MRI demonstrated a mass in the anterior mediastinum protruding into the superior vena cava (SVC) and right atrium. A diagnosis of thymoma was made by needle biopsy. The patient underwent surgery without preoperative treatment. The tumor extended across the capsule of hte thymic gland and a polypoid growth of tumor reached the right atrium through the lumen of the thymic and left brachiocephalic veins and the SVC. No direct infiltration into the SVC or pericardial cavity was observed. Under cardiopulmonary bypass, the tumor was resected with the left brachiocephalic vein, SVC, and the upper third of the right atrium. The SVC was reconstructed using an EPTFE graft. Histopathologic examination demonstrated a predominantly epithelial cell thymoma. Adjuvant chemotherapy was performed, and no recurrence has been recognized for 3 years postoperatively.

Use of vasoactive agents to increase tumor perfusion and the antitumor efficacy of drug-monoclonal antibody conjugates

The effects of both alpha 1- and beta-adrenergic blocking agents on the vascular perfusion of tumors were studied with the ultimate goal of improving diagnosis and therapy of solid tumors with the use of monoclonal antibody (MAb) conjugates. With the use of a subcutaneously growing murine thymoma, it was demonstrated that nonselective and cardioselective beta-adrenergic blocking agents were capable of increasing threefold tumor-to-blood and tumor-to-liver perfusion of 125I-labeled MAbs. Subsequently, these beta-adrenergic blocking agents were found to increase the antitumor efficacy of idarubicin (Ida)-MAb conjugates. Conjugate-treated mice that also received beta-adrenergic blocking agents had a smaller mean tumor size and a greater number of regressions than mice receiving Ida-MAb conjugate alone. By contrast, prazosin HCl, an alpha 1-adrenergic blocking agent, and Cyclospasmol, a peripheral vasodilator, did not enhance the tumor perfusion and antitumor efficacy of 125I- or Ida-conjugated MAbs, and no vasoactive agent enhanced the antitumor effect of Ida when used alone. By their selective action on normal blood vessels, vasoactive drugs can change the tumor-to-normal tissue perfusion ratio, thereby enhancing the access of drug-MAb conjugates to tumors and increasing the effectiveness of tumor therapy with the use of drug-MAb conjugates.

Differential diagnosis of anterior upper mediastinal expansions by contrast-enhanced computed tomography

This study investigated the potential of contrast-enhanced CT in the differential diagnosis of the most common anterior upper mediastinal expansions. CT examinations of 29 patients with an upper anterior mediastinal mass lesion of unknown origin were reviewed retrospectively and compared with the clinical data obtained. The density, contrast enhancement and invasive nature of the tumors were recorded. Thyroid tissue was enhanced most and lymphomas least. Contrast medium injection helped to distinguish great vessels and cystic lesions from surrounding areas. Thyroid tissue was most heterogeneous and lymphomas most homogeneous. All except one of the malignant neoplasms (a lymphoid mass lesion) were infiltratory in nature. Contrast-enhanced CT gives clues as to the origin of a neoplasm and whether it is benign or malignant.