Teaching Case

A 43-year-old female patient with a history of coeliac disease was referred to sonography due to an umbilical swelling. She reported an increasingly bloated abdomen and weight loss, diffuse abdominal discomfort and soft stools for several months. The umbilical swelling was cherry-sized, indurated, slightly purple and painful to touch.

Sonography of the umbilical lesion using a 10 MHz transducer was performed and showed an inhomogeneous irregular formation of approx. 2 x 2 x 1 cm and a discontinuity of the abdominal wall. The lesion remained unchanged at Valsalva manoeuvre, suggestive of an incarcerated hernia with unclear content (Fig. 1a, b).
However, this lesion seemed to be only part of a larger process, as additionally free intraabdominal fluid and a huge intraabdominal mass were found (Fig. 1b, c, d). This mass was inhomogeneous, with a partially hyper and hypoechogenic cystic-solid aspect, and extended ventrally of the intestinal loops over the middle and lower abdomen.
Further diagnostic work-up included an abdominal CT (Fig. 2) that showed the total extent of the intraabdominal mass and fluid, involving the whole abdominal cavity with perihepatic and perisplenic collections, the largest expansion can be seen in the ventral lower abdomen, reaching into the lesser pelvis.

A large intraperitoneal inhomogenous mass with intraperitoneal fluid is highly suspicious of a neoplastic aetiology and may represent pseudomyxoma peritonei (PMP) or peritoneal carcinomatosis (PC). PMP is a very rare condition caused by spreading of cells of malignant or benign mucinous tumours (e.g. mucinous adenoma or mucinous adenocarcinoma of the appendix or ovary) into the peritoneal cavity.

Clinical findings are unspecific like in this patient. Intraabdominal masses may be palpated. Imaging is therefore essential in the diagnosis of PMP.

A CT examination (preferably of the chest, abdomen and pelvis with intravenous and oral contrast) is the best diagnostic imaging tool in this indication. Tumour deposits on the visceral surfaces of the liver and spleen lead to the classical appearance of “scalloping”. Typically the small bowel is spared and may be surrounded by a massive “omental cake” seen as an inhomogeneously enhancing mass and mucinous ascites. [1] Peritoneal thickening, infiltration of the peritoneum and internal septation of the ascites may also be seen. In order to quantify the extent of PMP or PC a number of scoring systems have been developed of which the peritoneal cancer index (PCI) is most commonly used, which takes into account the distribution of tumour in the abdominopelvic regions and lesion size scores. [4]

Optimal treatment involves cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (HIPEC). The PCI can serve as a screening tool for patient selection where a PCI > 20 usually represents unresectable disease. [3] Prognosis is largely dependent on the success of cytoreductive therapy and 5-year survival ranges between 20 and 80%. [1]

In this patient a laparoscopic surgical exploration was done, showing ascites and vast mucous neoplastic coating of the whole abdomen. Histology and cytology showed no signs of malignant transformation. Cytokeratin expression patterns were typical for a gastrointestinal origin [2], especially a low-grade mucinous appendiceal neoplasia (LAMN). She was referred to HIPEC.

This case showed a rare presentation of PMP that was first detected by sonography as an incidental finding during the work-up of a presumed umbilical hernia. Imaging findings on CT were typical for PMP. Though the neoplastic cells seemed to be benign, the umbilical lesion may represent a metastasis or invasion of the abdominal wall.