ENHANCED BILATERAL SOMATOSTATIN RECEPTOR EXPRESSION IN MEDIASTINAL LYMPH-NODES (CHIMNEY SIGN) IN OCCULT METASTATIC MEDULLARY-THYROID CANCER- A TYPICAL SITE OF TUMOR MANIFESTATION

In medullary thyroid cancer (MTC), post-surgically elevated plasma cal citonin and/or carcinoembryonic antigen levels frequently indicate per sisting metastatic disease, although conventional diagnostic procedure s fail to localize the responsible lesions (occult disease). Somatosta tin analogues have been used successfully in disease localization, but recently concerns have been raised that increased thoracic uptake of indium-111 pentetreotide in patients with previous external beam irrad iation may represent a false-positive finding, caused by post-irradiat ion pulmonary fibrosis. We recently examined seven patients with metas tatic MTC by somatostatin receptor scintigraphy (six with occult and o ne with established disease). In four patients, all of whom had stable or slowly rising tumour marker levels over several years, a chimney-l ike bilateral mediastinal uptake of indium-111 pentetreotide was found . In two patients with persisting hypercalcitonaemia immediately after primary surgery supraclavicular lymph node metastases were identified as the responsible lesions. None of these seven patients had prior ex ternal beam radiation therapy. In two cases, histological confirmation was obtained. In one patient, disease progression could be shown duri ng follow-up. These data suggest that bilateral mediastinal lymph node involvement is a typical site of disease in slowly progressing occult metastatic MTC; the ''chimney sign'' may represent a typical finding with somatostatin analogues in such cases Therefore, we believe that e ven in the case of prior external beam irradiation, mediastinal uptake of octreotide might represent metastatic MTC rather than radiation fi brosis.