The patient felt generally well and remained active in several sports, but continued to have episodes of recurrent abdominal pain. Repeat contrast enhanced abdominal CT in July 2015 demonstrated a persistent pancreatic cystic lesion measuring 2.6 x 3.1 x 1.8 cm, with prior imaging not available for comparison at that time. Although a definitive diagnosis had not been established, due to his recurrent pain and persistent lesion, the patient underwent laparoscopic excision in July 2015. The patient tolerated the procedure well. The lesion was easily dissected from the pancreas. Macroscopically, it was noted to have four cystic components, ranging in size from 0.8 x 0.7 x 0.4 cm to 2.6 x 1.6 x 1 cm. Each cyst contained a white smooth wall filled with white, cloudy, watery fluid. Microscopically, the cysts were lined by a single layer of cuboidal to columnar epithelium with focal acini, with one cyst demonstrating internal concretions (Figure 3). No cytologic atypia or mitoses were present. These features were consistent with a multilocular ACA.
Figure 3. High powered magnification of cysts lined by a single epithelial layer of cuboidal to columnar epithelium with focal acini.
We have described a case of a young adolescent male with a multilocular ACA who underwent successful cyst excision. To our knowledge, he is the second youngest patient to have been reported with this lesion. Additionally, while nearly all previously reported cases of ACA resulted in extensive pancreatic resections including pancreaticoduodenectomy, lateral pancreatectomy, and total pancreatectomy, we have described a case with successful cyst excision without pancreas resection. Postoperatively, we have recommended every other year MRI/MRCP surveillance for this patient. Whether or not this is warranted or beneficial, especially given this patient’s young age at diagnosis, is unclear.
It has been proposed that ACAs originate from non-neoplastic acinar dilatation that expand into and incorporate ducts and ductules, eventually forming large cystic lesions as secretions accumulate. Ductal-to-acinar metaplasia has also been a theoretical explanation. More recently, however, pancreatic ACA has been described as an adenoma. While it has been suggested that this lesion is a precursor to acinar cell cystadenocarcinoma, the true malignant potential of this lesion remains unclear. To our knowledge, no case report or case series has reported evidence of malignant transformation of ACA with up to 7.8-year follow-up, regardless of whether or not the lesion was completely resected.
Although ACAs lack atypia and mitotic activity which seem to favor a non-neoplastic lesion, the discovery of multiple chromosomal gains on comparative genomic hybridization that contain a few cancer-associated genes and genomic instability suggest the lesion is preneoplastic. Additionally, a case of ACA with low-grade dysplasia was recently reported.
We know from previous studies that ACA are likely to grow over time. In a case series of 10 patients, 4 of whom underwent sequential imaging, all 4 cysts showed interval enlargement over time with a mean increase of 1.5 cm over 2.9 years. No postoperative recurrences have been reported. Until the course of ACA is better established, however, we believe these lesions should be aggressively monitored, with strong consideration for surgical resection to reduce the theoretical risk of malignant transformation. Given the rarity of these cysts, future studies to support this will likely be limited.
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