Ovarian mass as initial presentation of a gastric neuroendocrine tumour

Abstract

A 33-year-old woman presented with lower abdominal discomfort and a left adnexal mass on CT scan. Gross examination of the left ovary revealed an 80 mm solid yellow lobulated tumour with overlying serosal puckering. Histologically, the tumour consists of tubules and nests of epithelioid cells with oval nuclei, fine chromatin and 1 mitosis/10 HPF. A well-differentiated neuroendocrine tumour (NET) of the ovary was the favoured diagnosis since the tumour was positive for CK7, chromogranin A and negative for inhibin and CD99 which excluded the differentials of sex cord stromal and Wolffian tumours. Subsequent Gallium 68 octreotate PET imaging revealed tumours within the abdomen, pelvis and left breast. Total gastrectomy, partial pancreatectomy, splenectomy, hysterectomy, right oophorectomy and left breast lumpectomy were performed. A 72 mm grade 2 NET was found in the stomach with involvement of the pancreas, 10 of 25 lymph nodes, diaphragm, peritoneum, uterus and breast. The gastric tumour was positive for neuroendocrine markers, negative for CDX2, TTF-1 and pancreatic hormones, with 1 mitosis/10 HPF and Ki-67 index of 14%. The extent of extra-ovarian peritoneal disease favours a NET of gastric rather than ovarian origin. This case illustrates the challenge in distinguishing between primary and metastatic tumours of the ovary with unusual histology. In cases of NET, further investigations including medical imaging is essential to the work up of the patient.