Radionuclide lymphoscintigraphy with technetium 99m antimony sulfide colloid to identify lymphatic drainage of cutaneous melanoma at ambiguous sites in the head and neck and trunk.

Frequently the primary lesion of high-risk cutaneous melanoma (level III, greater than or equal to 1.5mm; greater than or equal to 1.0 mm with ulceration) is in an ambiguous lymphatic drainage site on the trunk, pelvic and shoulder girdles, and head and neck area. Lymphoscintigrams were performed by a circumferential intradermal injection of the biopsy site using technetium 99m (99mTc) antimony sulfide colloid in a total dose of 0.2 to 0.6 mCi in a volume of 0.1 to 0.5 ml. Imaging was done with a large-field gamma camera with high-resolution parallel hole collimator. Technetium 99m antimony sulfide colloid is an ideal agent for lymphoscintigrams because of small particle size (3-30 micron), which permits early migration into the interstitial space and lymphatics and rapid pickup by lymph nodes. Although it is a gamma emmitter with high activity, it has a short half-life and does not induce tissue necrosis. It does not localize the site of lymph node metastases, but indicates only the drainage pattern. Images were obtained at 1, 5, 10, 15, 30, and 60 minutes, respectively, and then three times every hour. Surgery was usually performed 24 hours later. The majority of patients had lesions with ambiguous drainage sites: head and neck (4 of 5 patients) and trunk (9 of 13 patients). The drainage by scan was to unpredictive sites in 72%, and resulted in a change of treatment planning by location and extent of ablation with node dissection in 9 of 18 patients. Ambiguous dissection sites included: (1) question of preauricular dissection with parotidectomy versus posterior auricular and cervical dissection for selected scalp lesions; (2) low-neck with or without axillary dissection for upper chest and shoulder lesions; and (3) axillary versus groin dissections for midflank lesions at zone of ambiguity between axilla and groin. It was concluded that preoperative 99mTc antimony sulfide lymphoscintigraphy is a highly useful planning technique in determining the appropriate lymphatic drainage basin for dissection in selected melanoma patients.