Malignant hemangioendothelioma demonstrated by thallium imaging

Thallium-201 scintigraphy is an effective diagnostic modality to distinguish malignant from benign soft-tissue tumors

BACKGROUND

The aim of this study is to evaluate whether thallium-201 (201-Tl) scintigraphy can differentiate malignant from benign soft-tissue tumors.

METHODS

Between April 1995 and December 2005, 192 patients with soft-tissue tumors (85 malignant and 107 benign) underwent 201-Tl scintigraphy before treatment. Isotope uptake was used as a proxy for tumor-to-background ratio (TBR). The accuracy of TBR on early and delayed imaging was evaluated using the Mann-Whitney U and χ(2) tests.

RESULTS

There was a statistically significant difference in mean TBR on early and delayed imaging of malignant and benign soft-tissue tumors (124% ± 109% vs. 22% ± 42%, and 82% ± 83% vs. 12% ± 25%, P < 0.0001). A TBR cutoff of 20% indicated the probability of malignancy on early and delayed imaging (82% sensitivity and 77% specificity; 82% sensitivity and 84% specificity, P < 0.0001). Well-differentiated liposarcomas showed low isotope accumulation, while pigmented villonodular synovitis and giant cell tumors of the tendon sheath showed high isotope accumulation.

CONCLUSIONS

Thallium-201 scintigraphy can distinguish malignant from benign tumors with relatively high accuracy. With the exception of low grade liposarcomas and locally aggressive benign tumors, 201-Tl scintigraphy may be an effective diagnostic modality to differentiate malignant from benign soft-tissue tumors.

Nuclear medicine techniques provide unique physiologic characterization of suspected and known soft tissue and bone sarcomas

Primary bone and soft tissue tumors have a range of physiologic, biochemical and genetic characteristics which differentiate them from benign tumors and normal tissues. These "fingerprints" are amenable to noninvasive detection and quantification using nuclear medicine techniques. Functional characterization using radiotracers imaged using a gamma camera or positron emission tomography (PET) can provide unique but complementary information to that provided by anatomically-based imaging modalities such as plain radiography, computed tomography (CT) and magnetic resonance imaging (MRI). This is particularly important following therapy when residual mass lesions may cause a dilemma regarding the need for further treatment. Lack of understanding of the role of functional imaging has impeded more rational use of nuclear medicine in this field. This review addresses the role of nuclear medicine techniques in the primary evaluation, staging, and therapeutic monitoring of soft tissue and bone sarcomas. The potential of delivering targeted radiotherapy to these tumors with radiopharmaceuticals which exploit the unique pathophysiology of each individual malignant lesion is also addressed.

Demonstration of blood flow patterns in human soft tissue sarcomas using 99mTc-labelled hexamethyl propyleneamineoxime

Blood flow patterns have been studied in 28 patients with soft tissue sarcoma (29 tumours) using 99mTc-labelled hexamethyl propyleneamineoxime with planar views of the tumour-bearing region. Tumour:background ratios ranged from 1.13 to 6.60 (mean 2.74) and maximum:minimum tumour ratios (between peripheries and centres of tumours) ranged from 1.34 to 32.0 (mean 4.70). In eight of 29 tumours (seven of which were involving the trunk) the tumour could not be identified. This study demonstrates that the blood supply to soft tissue sarcomas is generally greater than that to adjacent normal tissues and that tumour centres are relatively underperfused compared with the tumour periphery. In this heterogeneous series there was no clear-cut relationship between blood flow and histological grade or type.