Mucinous cystic neoplasm of liver masquerading as Hydatid cyst: Important lesson learned

Abstract

INTRODUCTION Mucinous cystic neoplasms of liver (MCN-L) are rare neoplasms comprising less than 5% of cystic lesions of liver.[1,2] They occur exclusively in females with mean age being 51 years. Recent WHO classification recommended that the term MCN L should be reserved for cysts with presence of an underlying ovarian stroma only.[3,4] We, hereby, present two cases, clinically and radiologically diagnosed as hydatid cyst and proven as MCN-L on histopathology. CASE REPORT 1: A 32-year-female presented with dull aching and non-radiating pain in upper abdomen for 1 month, associated with epigastric fullness. On USG abdomen, there was presence of large multi-loculated cystic lesion in right lobe of liver and on contrast enhanced computerized tomography (CECT), a well-defined cystic lesion with smooth wall and thin septae in segment III and IV of liver (10 × 10 cm) was seen, suggestive of hydatid cyst (HC). After robotic deroofing, gross examination revealed multiple flattened tissue pieces altogether measuring 5.2 × 5.4 × 5 cm. Microscopic examination revealed a multiloculated cyst lined by columnar epithelium having abundant intracytoplasmic mucin with underlying ovarian type stroma arranged in storiform and short fascicular pattern with strong nuclear expression of Estrogen Receptor alpha (ER) [Figure 1a and b]. In addition, few small interspersed cohesive clusters of epithelial cells were seen, positive for alpha inhibin and a diagnosis of MCN-L was rendered [Figure 1c].Figure 1: Cyst lined by low columnar epithelium with basally located nuclei and apical mucin with underlying ovarian-type stroma (a, Haematoxylin and Eosin 400x) showing diffuse nuclear immunopositivity for ER alpha and inhibin (b and c respectively, IHC 400x)2: A 57-year-female presented with dull aching pain in right upper abdomen since 6 months with a lump in right hypochondrium since 1 month, gradually progressive in size. Ultrasound followed by MRI abdomen was suggestive of a large cystic lesion (~13.6 × 12.4 cm) in segment IVB of liver, provisionally diagnosed as HC. Histopathology was suggestive of MCN-L with no features of high-grade dysplasia or malignancy with ovarian type stroma underneath epithelium. Patient was eventually lost to follow up. After 2 years she returned with complaints of pain in upper abdomen of 1-month duration. MRI abdomen showed persistent multilocuated cystic lesion in remaining segment IVB of liver measuring ~6.4 × 4.9 × 6.1 cm [Figure 2a and b]. Multiple enhancing internal septations were identified with maximum thickness of 2 mm. Resection of segment IVB and V with gall bladder was performed.Figure 2: Magnetic resonance imaging of liver – Axial T1 (a), T2 (b) weighted images show a T1 hypointense, T2 hyperintense unilocular cystic mass lesion (white arrows) involving segment IV, V of liver with clear fluid contents. Cyst is causing biliary compression with resultant bi-lobar intrahepatic biliary radical dilatation (black arrows)On gross examination, a cystic mass was identified measuring 7.5 × 6 × 3 cm and weighing approximately 66.4 gm, surrounded by liver parenchyma on all sides. On cut section, one multiloculated cyst was identified. On serial slicing cyst was partially solid and filled with greenish mucinous material. On microscopic examination, a cyst lined by single layer of bland, cuboidal to low columnar focally ciliated epithelium was identified [Figure 3]. Epithelium showed focal areas of ulceration with underlying stroma displaying extensive xanthogranulomatous reaction composed of sheets of histiocytes, foreign body type of giant cells and cholesterol clefts, possibly as a reaction to previous biopsy of the lesion. Stroma was composed of densely packed spindled cells, histologically mimicking ovarian-type stroma.Figure 3: (a) Low power view shows a cyst with underlying stroma (Haematoxylin and Eosin 100x). (b) High power view shows columnar epithelium with ovarian type stroma underneath (Haematoxylin and Eosin 400