We report an account of a difficult diagnosis, describing multiple adenomatoid tumours involving the liver and peritoneum in a patient with gastric adenocarcinoma. Two peritoneal tumours were found incidentally during laparoscopic staging and the liver lesion was subsequently detected at the time of gastrectomy. Frozen sections examination was performed initially on all of these lesions. They appeared pale and well circumscribed and measured between 0.2-0.5cm. Our diagnoses were based on morphological examination of haematoxylin and eosin stained paraffin sections, and was supported by histochemistry, immunohistochemistry and ultrastructural examination. On microscopic examination they all showed angiomatoid features, with tubular channels lined by vacuolated epithelioid cells set in a fibrous stroma. Signet ring-type cells were also identified, making distinction from metastatic adenocarcinoma difficult. Strong expression of lesional cells for broad spectrum cytokeratins and mesothelial markers was seen and ultrastructural examination showed characteristic microvilli, desmosomes and a collagenous stroma. Adenomatoid tumour is a benign neoplasm which is thought to be of mesothelial origin. These tumours are uncommon and are usually described in the genital tract, but also rarely at other sites. Multiple adenomatoid tumours occurring exclusively outside the genital tract have not previously been reported. We also report the first case of an adenomatoid tumour in the liver. We discuss the differential diagnosis and potential pitfalls encountered in the diagnosis of adenomatoid tumour at these sites, in particular the possibility of misdiagnosis of adenomatoid tumour as adenocarcinoma at frozen section.
- adenomatoid tumour
- electron microscopy