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Carney's triad is a rare non-hereditary condition characterized by gastrointestinal stromal tumors (GIST, intramural mesenchymal tumors of the gastrointestinal tract with neuronal or neural crest cell origin), pulmonary chondromas and extraadrenal paragangliomas.
Less than 100 cases have been reported worldwide. Carney's triad primarily affects young women (mean age of onset 20 years).
Most patients initially present with two of the three tumors (incomplete Carney's triad). The main symptoms at presentation are gastrointestinal bleeding, epigastric pain, anemia and palpable abdominal mass. These symptoms are related to the GIST, which occur in 99% of cases. Additional features include headaches, fatigue, anorexia, hypertension and tachycardia. Pulmonary chondromas (well-differentiated benign cartilaginous tumors) occur in approximately 80% of cases. They are often asymptomatic and may be unilateral (83%) or bilateral (32%). Secreting paragangliomas (typically extraadrenal and most often mediastinal) occur in approximately 50% of patients.
The etiology is not completely understood. Impaired succinate dehydrogenase (SDH) function resulting from chromosomal losses (but not mutations) has been detected in some patients with Carney's triad, while SDHD, SDHB or SDHC germline mutations have been found in some patients with Carney-Stratakis dyad (see this term).
Gastroscopy, radiography and computing tomography are the main diagnostic methods. SDH genetic testing is available. The absence of a paraganglioma, which usually completes the triad after several years (median: 6 years), does not allow exclusion of the diagnosis of Carney's triad. Iodine 131-metoiodobenzylguanidine scintigraphy and Octrescan® may help to detect paragangliomas.
The differential diagnosis should include Carney-Stratakis dyad.
Management and treatment
The treatment of choice for GIST and its metastases (overall rate: 50%) is surgical resection. GIST associated with Carney's triad are mostly indolent. Recurrence after surgery is found in approximately 50% of patients, with a mean interval after the initial presentation of 12 years. Imatinib mesylate, an effective agent in the treatment of GIST, is under investigation as an adjuvant treatment. Paragangliomas require surgical resection; chemotherapy and metabolic radiotherapy may be used in malignant cases (overall rate: 10%). Surgery for pulmonary chondromas is indicated only in case of impaired lung function. Approaches targeting SDH function may potentially be useful in treating patients with Carney's triad who show SDH deficiencies. However, at present, there is no drug that restores SDH function. Life-long follow-up should be offered to all patients with Carney's triad.