Carney complex is a multiple neoplasia syndrome featuring cardiac, endocrine, cutaneous, and neural tumors, as well as a variety of pigmented lesions of the skin and mucosae. Carney complex is inherited as an autosomal dominant trait and may simultaneously involve multiple endocrine glands, as in the classic multiple endocrine neoplasia syndromes 1 and 2. Carney complex also has some similarities to McCuneAlbright syndrome, a sporadic condition that is also characterized by multiple endocrine and nonendocrine tumors. Carney complex shares skin abnormalities and some nonendocrine tumors with the lentiginoses and certain of the hamartomatoses, particularly Peutz-Jeghers syndrome, with which it shares mucosal lentiginosis and an unusual gonadal tumor, large-cell calcifying Sertoli cell tumor. Careful clinical analysis has enabled positional cloning efforts to identify two chromosomal loci harboring potential candidate genes for Carney complex. Most recently, at the 17q22-24 locus, the tumor suppressor gene PRKAR1A, coding for the type 1alpha regulatory subunit of PKA, was found to be mutated in approximately half of the known Carney complex kindreds. PRKAR1A acts a classic tumor suppressor gene as demonstrated by loss of heterozygosity at the 17q22-24 locus in tumors associated with the complex. The second locus, at chromosome 2p16, to which most (but not all) of the remaining kindreds map, is also involved in the molecular pathogenesis of Carney complex tumors, as demonstrated by multiple genetic changes at this locus, including loss of heterozygosity and copy number gain. Despite the known genetic heterogeneity in the disease, clinical analysis has not detected any corresponding phenotypic differences between patients with PRKAR1A mutations and those without. This article summarizes the clinical manifestations of Carney complex from a worldwide collection of affected patients and also presents revised diagnostic criteria for Carney complex. In light of the recent identification of mutations in the PRKAR1A gene, an estimate of penetrance and recommendations for genetic screening are provided.

A genetic predisposition has been recognized for paragangliomas and adrenal or extra-adrenal pheochromocytomas was recognized years ago. Well known syndromes associated with an increased risk of pheochromocytoma include Von Hippel Lindau disease, multiple endocrine neoplasia type 2, and neurofibromatosis type 1 and are discussed elsewhere. The study of inherited predisposition to head and neck paragangliomas led to the discovery of three genes encoding subunits of the succinate dehydrogenase (SDH) enzyme (SDHB, SDHC and SDHD) thus opening an unexpected connection between mitochondrial tumour suppressor genes and neural crest-derived cancers. In this review we summarize the most recent knowledge about the role of SDH in tumorigenesis, including spectrum and prevalence of mutations, related phenotypes, and the biological hypotheses attempting to explain tumorigenesis, as well as current questions and ongoing research.

Carney triad (CT) describes the association of paragangliomas (PGLs) with gastrointestinal stromal tumours (GISTs) and pulmonary chondromas (PCH). A number of other lesions have been described in the condition including pheochromocytomas, oesophageal leiomyomas and adrenocortical adenomas; CT is a novel form of multiple endocrine neoplasia (MEN), a genetic condition with a female predilection. Inactivating mutations of the mitochondrial complex II succinate dehydrogenase (SDH) enzyme subunits SDHB, SDHC and SDHD have been found in familial and sporadic PGLs, and gain-of-function mutations of the oncogenes c-kit (KIT) and platelet-derived growth factor receptor A (PDGFRA) cause sporadic and familial GISTs. We recently reported an international series of patients with CT, 34 females and three males (median age of presentation 21 years) who did not carry SDHA, SDHB, SDHC, SDHD, KIT or PDGFRA gene mutations. Comparative genomic hybridization revealed a number of DNA copy number changes. The most frequent and greatest contiguous change was a deletion within the 1pcen13-q21 region, which harbours the SDHC gene. Another frequent change was loss of 1p. Although GISTs showed more frequent losses of 1p than PGLs, the pattern of chromosomal changes was similar in the two tumours despite their different tissue origin and histology; the findings were consistent with a common genetic aetiology of these two tumours in CT. In a separate condition, in which the association (or dyad) of GISTs with PGLs is inherited in an autosomal dominant manner (Carney–Stratakis syndrome, CSS), germline mutations of the SDHB, SDHC and SDHD genes (but not KIT or PDFGRA) were found; GISTs in this condition were caused by SDH deficiency. We conclude that CT is a novel MEN syndrome whose genetic defect remains elusive. CSS is caused by SDH defects, suggesting that sarcomas (GISTs) can be caused by defective mitochondrial oxidation, consistent with recent data implicating this enzyme in a variety of endocrine and other tumours. The above have clinical implications (i) for patients with GISTs that are cKIT- and PDGFRA-mutation negative: these tumours are usually resistant to treatment with currently available tyrosine kinase inhibitors and may be part of a syndrome such as CT or CSS; and (ii) for patients with an inherited PGL syndrome, family history should be explored to identify any other tumours in the family, and in particular other endocrine lesions and GISTs.