Intracystic papillary carcinoma is a distinct entity. Current controversy exists over whether
this is an in-situ or invasive tumour. It should be clearly distinguished from in situ or DCIS
papillary carcinoma. Intracystic papillary cancer is an invasive tumour within a thick cyst
cavity. Usually these cancers are small (between 1 and 3 cm in size). Mucin secretion may
or may not be seen. Pure types behave in very low-grade fashion and rarely metastasise.