Carotid Paragangliomas Related to Form Involving Multiple Systems (Syndromes and Diseases): A Systematic Literature Review

Carotid paragangliomas are infrequent tumours, generally single, non-functional and benign. Nevertheless, the biology of these tumours occasionally means they are bilateral, multicentric, functional and malignant. Such infrequency and the different ways they manifest themselves pose a diagnostic/therapeutic challenge that is reflected in the final outcomes. According to the Shamblin classification, 75% of carotid paragangliomas are either Type I (tumour smaller than 4 cm, weakly attached to the carotid arteries, and can be surgically excised in a straightforward manner) or Type II (tumour larger than 4 cm, partially surrounding the carotid arteries, and attached to the vascular adventitia), and 25% of cases are Type III, completely surrounding the carotid bifurcation, firmly attached, so vessel replacement may be considered. Fewer than 5% of carotid paragangliomas are associated with syndromes (e.g., von Hippel-Lindau disease and Carney triad) or diseases (e.g., thyroid cancer and thymoma), which further complicate their treatment. Morbidity and mortality rates in these cases are clearly different. This review sets out to address carotid paragangliomas related to syndromes and diseases, with their references being very widely distributed in the literature, with the aim being to highlight their idiosyncrasies of clinical, diagnostic and therapeutic interest. This has involved a systematic literature review of the Medline and Cochrane Library databases up to 1 November 2019, locating 26 articles involving a total of 37 patients. Conclusions: 1) Patients with these exceptional combinations present major clinical complexity; 2) They pose a medical challenge, with the diagnostic strategy being vitally important (search for associated synchronous and metachronous tumours) together with the therapeutic process (surgical times and priorities); and 3) There must be interdisciplinary cooperation across the different medical specialisms involved.