Carcinoid ovary with synchronous carcinoid tumour of the appendix: report of a rare occurrence with review of literature.

Carcinoid tumours are present in a wide range of organs but most frequently involve the gastrointestinal tract and rarely reported in gynaecological organs. Literature reports that the prevalence of ovarian carcinoid is 0.3%-1% of ovarian neoplasms and accounts for only 5% of ovarian teratomas. The pathogenesis of neuroendocrine tumours associated with synchronous primaries is undetermined and many theories have been proposed, such as existence of a common carcinogenic effect or a common stem cell undergoing similar genetic mutation. Paracrine or autocrine growth loop effect by the secretory peptides of the neuroendocrine cell tumours is also suggested. Since carcinoids are variably positive in neuroendocrine and organ-specific markers, there are no immunohistochemistry markers to delineate the definite primary site of origin versus metastasis. We report a rare case of carcinoid ovary with synchronous carcinoid tumour of the appendix. In our case, the presence of contralateral teratomatous elements may hint primary struma carcinoid instead of being metastatic from the appendix. A strumal carcinoid component was also highlighted by PAX8 positivity. This led us to conclude the case as concurrent appendix carcinoid with struma carcinoid as two independent primaries with uncertain pathogenesis. Histologically, as both tumours are well differentiated with Ki-67 of less than 3%, the decision of the joint tumour board was to keep the patient on surveillance, with no adjuvant treatment needed. The patient is currently on surveillance and the follow-up period of 24 months to date has been uneventful.