The speed of cyst growth predicts whether branch duct intraductal papillary mucinous neoplasms (Br-IPMNs) will become malignant, according to a study by Mee Joo Kang et al. in the January issue of Clinical Gastroenterology and Hepatology.
IPMN is a premalignant pancreatic lesion that progresses from adenoma to carcinoma; cysts are detected by imaging, but little is known about which ones are most dangerous. Some studies have proposed that patients with an asymptomatic Br-IPMN cyst smaller than 3 cm, without mural nodules or abnormal cyst fluid cytology, have less than a 20% risk of malignancy.
Kang et al. followed 201 patients diagnosed with Br-IPMNs who had an initial cyst smaller than 30 mm for more than 3 months, and examined them by computed tomography at least twice. Their mean cyst growth rate was 1.1 mm/year. Eight of 35 patients who received surgery developed malignant cysts, which were greater in final size than nonmalignant cysts (24.3 mm vs. 16.9 mm); the malignant cysts also grew by a greater percentage (69.8% vs. 19.4%) and at a greater rate (4.1 mm vs. 1.0 mm/year). After 5 years, cysts that grew more than 2 mm/year had a 45.5% risk of malignancy, compared with 1.8% for cysts that grew more slowly; emergence of a mural nodule during the 5-year follow-up period increased risks of malignancy by 41.3%.
Previous studies reported that only 6% to 16% of cysts increase in size, but Kang et al. found that 40.8% of cysts grew by more than 20%. Smaller cysts had greater growth rates, and 60% of patients who developed mural nodules during the follow-up period had an initial cyst size of 20 mm. These findings indicate that even small Br-IPMNs need constant surveillance.
Kang et al. warn that patients with rapidly growing cysts have a large risk for developing malignant tumors, and that the presence of mural nodules increases this risk. On the other hand, patients with Br-IPMNs of 20 mm or less that grow less than 2 mm/year, without a mural nodule, have low risk for malignancy and can probably be observed.
More Information on IPMNs:
Read the article online:
Kang MJ, Jang J-Y, Kim SJ, et al. Cyst growth rate predicts malignancy in patients with branch duct intraductal papillary mucinous neoplasms. Clin Gastroenterol and Hepatol 2011;9:87–93.