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Nondetection of Sentinel Lymph Node with Lymphoscintigraphy as a Result of Massive Malignant Invasion Shown by Positron Emission Tomography

Blocklet, Didier, M.D.*; Donckier, Vincent, M.D., Ph.D.; Vereecken, Pierre, M.D.; van Geertruyden, Jean, M.D.; Laporte, Marianne, M.D.; Goldman, Serge, M.D., Ph.D§

Original Articles

Purpose  The authors report the complementary roles of lymphoscintigraphy in sentinel node mapping and F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in a massively invaded sentinel node.

Materials and Methods  A 49-year-old woman was referred to the authors’ institution after the resection of a malignant melanoma (Clark IV, Breslow 5.25) of the right buttock. No evidence of regional or distant organ metastases was observed on bone scintigraphy or thoracoabdominal or cerebral computed tomographs. Preoperative lymphoscintigraphy showed drainage around a circular structure, without any node detected. F-18 FDG PET imaging detected an area of focal, markedly hypermetabolic activity at the same location.

Results  The focal, markedly hypermetabolic activity detected by F-18 FDG PET corresponded to a massively invaded sentinel node not shown by lymphoscintigraphy but found and removed at the time of surgery. Radical regional lymphadenectomy showed only one small additional lymph node micrometastasis detected after immunohistochemical staining for S-100 protein and HMB45 antigen.

Conclusions  This case emphasizes the complementary roles of lymphoscintigraphy sentinel node mapping and F-18 FDG PET. Indeed, a massively invaded sentinel node may be detected by PET but missed by lymphoscintigraphy.

From the Departments of Nuclear Medicine,* Surgery,† Dermatology,‡ and the PET Biomedical Cyclotron Unit,§ Université Libre de Bruxelles, Hôpital Erasme, Brussels, Belgium

Received for publication December 28, 2000.

Revision accepted August 15, 2001.

Reprint requests: Dr. Didier Blocklet, Service de Médecine Nucléaire, U.L.B. Hôpital Universitaire Erasme, 808 route de Lennik, 1070 Brussels, Belgium. E-mail:

© 2001 Lippincott Williams & Wilkins, Inc.