Contributed by Paulo A. Carvahlo, M.D., Ph.D.

Melanoma ranks behind lung and breast carcinoma as the third most common tumor that metastasizes to the brain. Autopsy series show that the brain is involved in 36% to 54% of the cases of distant metastatic melanoma. Sites more frequently involved include the skin, subcutaneous tissue, lymph nodes, lungs and liver. In clinical series, brain involvement is less frequent (12% to 20%), but the order of organ involvement is the same, suggesting that the clinical evaluation of patients often underestimate the extent of metastatic disease and actual tumor burden . The hemispheres are usually equally compromised, with the frontal lobe being more frequently involved. Solitary lesions are present in approximately 25% of cases. Cerebral metastasis have a propensity for hemorrhage (33% to 50% of the patients). The median survival time for patients with cerebral metastasis is in the order of 2 to 6 months (1).

The diagnostic evaluation for possible metastatic disease should include plain radiographs of the chest, blood count and liver function tests including LDH. Other imaging studies rarely reveal metastasis when patients are symptom free. Recently, however, staging of malignant melanoma with whole-body positron emission tomography and 2-F18-fluoro-2-deoxy-D-glucose (FDG PET) and the characterization of lymphatic drainage with lymphoscintigraphy have been shown to improved early detectability, which may impact prognosis and patient management (2,3). In patients with CNS symptoms, the best single test for the diagnosis of cerebral metastases is either MRI or CT scans with contrast. MRI seems to better distinguish hemorrhage from tumor (1). In the case described above, there was prominent uptake of both tracers Tl-201 and Tc-99m HMPAO in 3 out of 4 lesions. The right temporal lesion was small and nondetectable with present SPECT technology. These findings indicated that viable metastatic tumor was present in these sites after initial treatment and that the previously hemorrhaged lesion showed prominent uptake in an anatomical site that favored surgical resection. The dual isotope scan was useful in demonstrating tumor viability and perfusion.

Cerebral metastasis of malignant melanoma have shown Tl-201 utapke in a number of reported cases using both planar and SPECT images (4,5). Cerebral perfusion agents such as I-123 iophetamine and Tc-99m HMPAO have also been shown to accumulate in these lesions (6-8). I-123 IMP shows significant uptake, while Tc-99m HMPAO accumulates less intensely. Click here to study an example of intense Tc-99m HMPAO uptake in both treated and untreated lesions.

References

1. DeVita VT, Hellman S, Rosenberg SA. Cancer: principles and practice of oncology. 4th Edition, J. B. Lippincott Co., Philadelphia, 1993.
2. Steinert HC, Böni RAH, Buck A et al. Malignant melanoma: staging with whole-body positron emission tomography and 2-[F-18]-fluoro-2-deoxy-D-glucose. Radiology 1995;195:705-709.
3. Uren RF, Howman-Giles RB, Shaw HM, Thompson JF, McCarthy WH. Lymphoscintigraphy in high-risk melanoma of the trunk: predicting draining node groups, defining lymphatic channels and locating the sentinel node. J Nucl Med 1993; 34:1435-1440.
4. Ancri D, Basset JY. Diagnosis of cerebral metastases by thallium-201. Br J Radiol 1980;53:443-445.
5. Krasnow AZ, Collier BD, Isitman AT, Hellman RS, Peck DC. The clinical significance of unusual sites of thallium-201 uptake. Semin Nucl Med 1988;28:350-358.
6. Nagel JS, Ichise M, Mueller SP, Johnson KJ, English RJ, Kaplan WD, Schober O, Holman BL. Increased iofetamine I-123 brain uptake in metastatic melanoma. Arch Neurol 1988;45:1126-1128.
7. Cohen MB, Saxton RE, Lake RR, Cagle L, Graham LS, Nizze A, Yamada LS, Gan M, Bronca G, Greenwell K, Morton DL. Detection of malignant melanoma with Iodine-123 iodoamphetamine. J Nucl Med 1988;29:1200-1206.
8. Suess E, Malessa S, Ungersböck, Kitz P, Podreka I, Heimberger K, Hornykiewicz O, Deecke L. Technetium-99m-d,l-hexamethylpropyleneamine oxime (HMPAO) uptake and glutathione content in brain tumors. J Nucl Med 1991;32:1675-1681.

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Last updated: Aug 23, 1995 Redesigned June 1998