Discussion:
The incidence of biliary cystadenoma ranges between 1:20,000 and 1:100,000, although the malignant counterpart is even rarer with an estimated incidence of 1:10 million [5]. These are generally sporadic in nature [6]. The exact origin of the neoplasm is unknown. Two schools of thought say that either they are derived from ectopic ovarian tissue or from ectopic embryonic gallbladder rests [7]. Estrogen-receptor positivity in the dense ovarian stroma points towards the hormonal dependence in the tumorigenesis [8]. This could very well explain its exclusive occurrence in females. Clinically it can present with non-specific symptoms like epigastric pain, vague abdominal discomfort obstructive jaundice, or even ascending cholangitis [9]. Although these were not the case for us. Here the tumor was big enough to compress the stomach to cause clinical features of gastric outlet obstruction. Moreover as it was extramural and partial obstruction, electrolytes were within normal limits.
Noninvasive imaging modalities like computed tomography (multiloculated lesion, internal septation, papillary projections, intramural nodule, septal enhancement), endoscopic or transabdominal ultrasound helps in characterising the lesion, but a definitive diagnosis can only be attained after histopathological evaluation. It our case these investigations failed to point out the origin of the tumor. Intraoperatively the origin of the tumor was made out and the surgeons took a call to modify the treatment plan as stated above. Preoperative needle aspiration or needle biopsy is not routinely performed as it increases the risk of secondary infection, intra-cystic bleeding, rupture of cyst, needle seeding of tumor cells and dissemination which may complicate the diagnosis and further management. Although in our case the preoperative diagnosis was thought to be pancreatic cystic lesion and differentials considered for that were cystic neoplasms and pseudocyst. Hence cystic fluid aspiration was done to distinguish them.
Surgical excision (complete) is the treatment of choice and other treatment modalities like partial resection, marsupialization, fenestration and sclerosis are shown to be associated with recurrence with a rate which can be as high as 10% to 90% [10].
Resected specimen on histological examination gives the definitive diagnosis. The cysts are lined by gastric or biliary columnar epithelial cells with apical mucin. Dense ovarian stroma is also another hallmark finding which suggests benign nature of the disease with good prognosis where as its absence suggests poor prognosis [11]. Immunohistochemistry is also beneficial to better characterise the tumor and is done when the histopathology is inconclusive.