Discussion:
Lymphangiomas are the cystic dilatation, due to malformation (congenital) or fibrosis (acquired), of lymphatic channels. These are benign slow-growing cystic masses that cause lymphangiectasia due to lymphatic flow blockage. Gui et al described these segregated lymphatic channels as defective channels formed during the embryonic period rather than a true neoplasm [1]. These are generally reported in young children and are linked with congenital disruption syndromes such as Turner syndrome, Down syndrome, and Noonan syndrome [2]. During the development of an embryo, the disconnection of lymphatic vessels results in lymph obstruction that is enveloped by endothelial cells [3]. As a result of this multiloculated lymphangiomas are formed. Whereas acquired lymphangioma developed due to fibrosis, inflammation, and lymphatic vessel degeneration [4]. Frequently these lesions are found in the upper parts of the body mainly the neck and head (75%), axilla (15%) [5, 6, 7], unusual sites are the pericardium, pleura, liver, spleen, colon, groin, genital organs, and bones. Lymphangiomas developing in the adult pancreas comprise less than 1% of all Lymphangiomas [8].
Until now, only a few cases of lymphangiomas have been reported. The first case was described by Koch K, in 1913 a benign cyst formed due to blocked regional lymphatic ducts [9]. In medical literature, to our best knowledge, less than 85 to 90 cases have been described [10].
Clinical manifestation of pancreatic lymphangiomas is nonspecific and varies based on the site and size of the cyst[11]. Usually, they are symptomless and found as incidental findings [8]. when symptomatic are present, they are in the form of digestive discomfort, pain in the upper abdomen, or palpable masses. Although benign may invade the adjacent structure and when involve bordering structures like adrenal gland patient presents with specific symptoms like acute renal injury with the breakdown of skeletal muscle fibers.[12]
Hence, the combination of clinical presentation and laboratory evaluation may help identify the origin of the tumor and make appropriate diagnoses and differentials. In our case, the patient was symptomatic, he was a male patient who came with complaints of epigastric pain for few days. The average size of pancreatic lymphangiomas is around 12 cm in the greatest dimension [13], but in our case, the lesion was relatively larger. For evaluation, the CT pancreas dynamic was performed which revealed a multilocular and multiseptated homogeneously hypoattenuating/non-enhancing fluid density omento mesenteric mass predominantly occupying the lesser sac. The lesion was insinuating within the pancreatic body and tail parenchyma as well as along the small bowel mesentery with mild mass effect on the stomach which is anteriorly compressed. It was abutting the left adrenal gland, which was however normal. The pancreatic head and uncinate process appeared normal. It was causing displacement of the small bowel loops and surrounding the transverse colon and splenic flexure.
Generally, pancreatic cystic lesions can be differentiated from lymphangiomas include pancreatic simple cysts pseudocysts, mucinous cystic neoplasms, serous cystadenomas, intraductal papillary mucinous neoplasms, and cystic pancreatic carcinomas. Imaging results may assist in preoperative diagnosis of upper abdominal lymphangiomas, even though none of the findings are confirmatory [13]. On Ultrasound scan, lymphangioma gives the impression as a complex cystic mass with intra-cystic septation or internal echoes, with or without internal calcifications. CT scan will reveal a low-density, thin-walled, uni, or multilobulated cystic mass with thin enhancing endo-cystic septation [8]. pancreatic cystadenomas share the same imaging findings and may present in similar ways suspension, can be ruled out on histology. Pseudocyst in the pancreas usually develops due to chronic or acute pancreatitis, USG or CT imaging will reflect the finding. These changes were not present in our case and therefore the possibility of pseudocyst was low.
Diagnosing pancreatic lymphangioma is highly suspect with the help of clinical findings and imaging investigations like CT, and EUS combined with FNA. In our case after clinical evaluation, we did CT which narrow down our differentials and leads us to ultrasound-guided Fine Needle Aspiration (FNA). Aspirated fluid was sent for cytology and biochemistry yielding very high LDH and triglyceride levels, making pancreatic lymphangioma highly likely and our working diagnosis. Simple cysts, serous cysts, or lymphangiomas usually yield clear thin, straw-colored fluids, composed of lymphomononuclear cells. Fluid from mucinous cysts will produce mucin, which can be detected grossly and microscopically. Moreover, the aspirated fluid from mucinous cyst will show mucin-producing columnar epithelial cells in varying amounts, arranged in papillae, clusters, or singles, these cells may or may not show cytological atypia. pancreatic Cystic carcinomas characteristically exhibit cytologically and morphologically malignant cells arranged in clusters, acinar or papillary patterns [8,13,14]
A definitive diagnosis is made on histopathological examination. Grossly cystic lymphangiomas are typically soft multilobulated masses containing serosanguinous or serous fluid. The cyst walls are usually single-layered cells without any solid areas. Under microscope dilated lymphatic channels of large and small sizes are seen, which are separated by thin septa and are intermixed with the pancreatic parenchyma [13]. Cysts are lined by flattened endothelial cells. Lymphocytes aggregates may be noticed inside the cysts or adjoining stromal tissues in Lymphangiomas [8,13]. Histologically lymphangiomas are classified into cystic, cavernous, and capillary [4, 7 15]. This classification was defined by Wegner in 1877 [16]. 2018 International Society for the Study Vascular Anomalies, subclassify the cystic lymphangioma as macro-cystic lymphatic malformation if cyst diameter is more than 1 cm, while cavernous lymphangioma is described as microcystic lymphatic malformation as the cyst diameter is less than 1 cm. Thus, lymphangiomas are classified into microcystic, macrocytic, and mixed lymphangiomas [17]. Capillary lymphangiomas are formed by tiny, poorly defined lymphatic vessels comprising of a thick cellular stroma [7]. Microcystic lymphangiomas are common in areas with dense connective tissue so decreased muscle expansion, such as the tongue and lip. Macro-cystic lymphangiomas are more common in areas with loose connective tissue, like the axilla, neck, and abdomen, so endothelial-lined channels can easily expand. [18]. Retroperitoneal macro-cystic lymphangiomas are predominantly multilocular [7]. In the pancreas, cystic and cavernous and a mixture of these two have been reported.
The treatment of lymphangioma is based on classification. In macrocytic or mixed lymphangiomas spontaneous regression usually occurs while it is rare in microcystic lymphangioma. Old age is more likely associated with spontaneous [19]. Pathologically, mixed lymphangiomas macrocystic are comparable but vary from microcystic lymphangioma in the balance of in and outflow of lymph fluid [19]. In microcytic lymphangioma, surgery is a reasonable approach because of the lack of spontaneous regression. While if the patient remains asymptomatic and the lesion is not increasing, the patient can be managed conservatively with regular surveillance imaging studies. Surgical resection is the definitive treatment of lymphangiomas.
Different surgical choices may be considered, like simple cyst excision, total pancreatic resection, (Whipple procedure or distal pancreatectomy), which depends on the size and morphology of the cysts [14]. En-bloc resection of the pancreatic lymphangioma is the treatment of choice, which was done in the present case. Partial removal of cyst or aspiration of the content of cyst is not recommended because it may cause recurrences. Long term prognosis as complete resection of the pancreatic lymphangioma is excellent [13,20].