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The three cases reported here illustrate the diagnostic, therapeutic and prognostic problems raised by these tumours. These are rare lesions with little suggestive symptoms, which explains why they are exceptionally diagnosed before surgery. Mucosal hyperplasias and cystadenomas are benign formations with a 90-100% survival rate 5 years after appendicectomy, even when non-cellular mucoid effusion is present. Cystadenocarcinomas are malignant tumours with mucoid secretion containing epithelial cells; they have a tendency to recur despite repeated evacuations, and their 5-year survival rate is approximately 25%; death results from intestinal obstruction or compression of intra-abdominal viscera by the mucoid substance.

Alkaline phosphatase (AP), gamma-glutamyl transpeptidase (GGT), lactate dehydrogenase (LDH) and aspartate aminotransferase (AsT) assays, as well as ultrasonography are the easiest and least expensive examinations to perform in the diagnosis of hepatic metastases. The 273 patients included in this series had cancer of the digestive tract. The diagnosis of presence or absence of liver metastases was made at surgery and was positive in 38 patients (14 per cent). A receiver operating characteristic (ROC) curve was drawn after computing the sensitivity (Se) and specificity (Sp) of each laboratory determination while the threshold indicating that the value was normal was incremented. The examinations were then compared in terms of Se, Sp, positive predictive value and negative predictive value. The threshold was determined on the ROC curve where less false-positive and more true-positive results were shown. According to predictive values, laboratory determinations could be classified in decreasing order of usefulness as: AP, LDH, GGT and AsT. Ultrasonography had a positive predictive value of 68 per cent a negative predictive value of 95 per cent, both figures being higher than those of any laboratory examination. These results suggest that ultrasonography has a higher diagnostic value than any of the enzyme assays in the detection of hepatic metastases. Moreover, ultrasonography provides morphological information which, in case of liver resection, may be useful to the surgeon.