AXILLARY LYMPH-NODE UPTAKE OF TECHNETIUM-99M-MDP

We sought to determine the frequency and significance of axillary lymp h node visualization on bone scans performed with diphosphonates. Meth ods: Consecutive Tc-99m-methylene diphosphonate (Tc-99m-MDP) bone scan s (2435) were inspected for axillary soft-tissue uptake. In positive c ases, the results of physical examination, correlative imaging studies and serial bone scans were recorded, as was the site of venipuncture. Results: Forty-eight studies (2%) showed axillary uptake ipsilateral to the injection site. Extravasation of tracer, documented by focal ac tivity near the injection site, was present in every case. There was n o association with axillary adenopathy, mass, induration or radiograph ically visible calcification. On some images, foci adjacent to the axi lla were superimposed on the rib, scapula, or humerus. The bone-to-bac kground ratio was frequently reduced; repeat imaging after 1-2 hr usua lly improved osseous detail. Conclusion: Ipsilateral axillary lymph no de visualization due to extravasation of Tc-99m-MDP is frequently asso ciated with additional foci superimposed on osseous structures simulat ing pathology. Delayed skeletal uptake is common in such cases and nec essitates a greater time interval between injection and imaging.