**5.1 Pathology of ovarian mucinous carcinomas**

Ovarian mucinous carcinomas are usually unilateral masses, large in size (8–40 cm), with the presence of unilocular or multilocular cysts filled with mucinous content. These tumours may display a variety of lesions from cystadenoma areas to borderline mucinous tumour regions and carcinomatous components. Microscopically there are two major histotypes, the intestinal and the endocervical. The intestinal type is more common than the endocervical. They exhibit glandular, cribriform, papillary and solid patterns of growth with two different patterns of invasion (i) expansile/confluent (more common) with a back-to-back glands labyrinthine complex appearance and minimal stroma and (ii) infiltrative/destructive characterised by irregular malignant glands infiltrating desmoplastic stroma. Each pattern of invasion measures 5 mm or more in linear size and they may coexist [5, 108]. Rarely, mural nodules of anaplastic carcinoma or high-grade sarcomatous-like component may be seen in ovarian mucinous carcinomas [5, 110]. There is no standardised grading system for OMCs till now.
