To date, at least eight guidelines or statements for the management of PCNs, or more specifically IPMN and MCN, have been published in the English literature. Since no significant data exist from prospective studies yet, all the guidelines and statements are based on a critical review of available data and consensus of experts.

Adequate methodologies and intervals of surveillance of BD-IPMN to check the malignant changes and/or the development of concomitant but distinct PDAC remain to be determined. Fukuoka consensus recommended yearly follow-up for cysts <10 mm, 6–12 monthly follow-up for cysts 10–20 mm, and 3–6 monthly follow-up for cysts >20 mm [16]. Fukuoka consensus advocated lengthening of the surveillance interval after 2 years of no change on images, whereas it suggested not to lengthen the intervals >6 months in view of the relatively high incidence of concomitant PDAC mentioned above. A French group claimed the adequacy of lengthening of the surveillance intervals in view of a low incidence of the malignant change in IPMN, yet they recommended biannual imaging studies [29]. Tamura et al. [30] showed that even a 6-month interval might be insufficient for the timely diagnosis of a concomitant PDAC in a patient with IPMN.

Whether we can stop surveillance of patients with BD-IPMNs or not, and, if yes, when to stop remain debatable. It is surely useless to continue surveillance of those who cannot be candidates for surgery. However, the chronological age per se, 85 years old, for example, should not be taken as the limit for surveillance, because the medical condition of each patient is different.

The American College of Radiology recommended stopping the surveillance after 2 years when a small cyst shows no change [10]. Fukuoka consensus stated that there were no good long-term data to indicate whether surveillance can be safely spaced to every 2 years or even discontinued after long-term stability [16]. Recently, the AGA guidelines have recommended quitting surveillance when a cyst does not show a significant change in 5 years, if high-risk features are completely negated and the patient does not have a strong family history of PDAC [14]. They state that the small risk of malignant progression in stable cysts is likely outweighed by the costs of surveillance.

However, these recommendations to stop surveillance of BD-IPMNs are now questioned as there are no long-term data to support this concept, and moreover, there are so many reports of retrospective studies addressing the long-lasting risk of development of concomitant pancreatic cancer in patients with IPMNs and a history of IPMNs [30–60]. Khannoussi et al. [46] found two PDACs concomitant with IPMN both after 84-month follow-up and concluded that imaging surveillance was still necessary beyond 5 years. Likewise, Lafemina et al. [49] also noted that 5 of the 18 patients with invasive carcinoma found in 97 patients with BD-IPMN resected developed PDAC in a region distinct from monitored IPMN (5.2%) and stressed the importance of consideration of risk not only to the index cyst but also to the entire gland in surveillance strategy of IPMN. The significance of indefinite surveillance was repeatedly noted as early as in the 2000s as well [61, 62]. He et al. [50] also emphasized that patients who have undergone resection for noninvasive IPMN require indefinite close surveillance because of the risks of developing a new IPMN, of requiring surgery, and of developing cancer (0%, 7%, and 38% at 1, 5, and 10 years, respectively). More recently, Miyasaka et al. [58] also stated that the incidences of both malignant IPMN and concomitant cancer rise further even after 5 years.