Casual discovery of Tc-99m MDP uptake for melanoma metastasis in soft tissue

The authors report the casual discovery in 1991 of a metastasis during Tc-99m MDP imaging of a 57-year-old woman who underwent surgery in 1983 for cutaneous melanoma on the right calf. The scan did not show bone alterations but did reveal an area of hyperactive uptake in the soft tissue of the medial surface of the thigh, where slightly altered pigmentation was also apparent. A subsequent immunoscan with Tc-99m-F(ab')2 225.28S confirmed increased uptake at this site. The lesion was removed and was histologically diagnosed as a skin metastasis from melanoma. Inguinal adenopathy appeared 6 months later. The uptake of Tc-99m MDP by both primary and metastases tumors has been described, although this may be the first report concerning melanoma. The uptake mechanism is not known.