Editing CUA: Cystic Renal Lesions (2017) (section)

== Role of active surveillance for suspected cystic RCC ==

* '''The vast majority of cystic RCCs are multilocular cystic RCCs (mcRCC,)''' but all RCC subtypes may present in a predominantly cystic form. '''Cystic RCCs need to be distinguished from solid renal masses with necrotic components, which behave more aggressively.'''
* '''mcRCCs have consistently better cancer-specific and overall survival compared with solid RCCs.'''
** '''There is yet to be a report demonstrating metastases or recurrence of mcRCCs.''' To reflect this indolent behaviour, the International Society of Urological Pathology (ISUP) has recently modified its terminology and now recommends calling these lesions multilocular cystic renal neoplasm with low malignant potential.
** One potential explanation for this better prognosis is that the majority of mcRCCs tumour volume is fluid and thus, the actual tumour burden is much lower when compared to similar sized solid tumours. As the outcomes of these tumours do not seem to be influenced by the overall lesion size, some experts have even suggested to abandon the current pathological T staging for mcRCC and to reassigned them a new stage called pT1c (c for cystic).
* '''Given their relatively indolent nature, there is emerging evidence suggesting that these lesions (especially Bosniak classification III) can be safely managed by active surveillance.''' If active surveillance is considered, it seems reasonable to follow these lesions with abdominal imaging every 6 months for the first 2 years, followed by yearly imaging thereafter, if the lesion is stable.
* '''Triggers for interventions are yet to be clearly defined and validated, but may include:'''
*# '''Progression from Bosniak III to IV'''
*# '''Growth of solid nodule > 3 cm'''
*# '''Fast-growing nodule'''