Low-grade mucinous epithelial neoplasm (intestinal type) arising in a mature sacrococcygeal teratoma with late recurrence as pseudomyxoma peritonei

Mucinous epithelial neoplasms associated with mature teratomas are well described in the gonads, and some examples have presented with clinical pseudomyxoma peritonei. The association between pseudomyxoma peritonei and an extragonadal teratoma is limited to a single case report. We describe a mature teratoma in the sacrococcygeal region associated with an intestinal-type mucinous epithelial neoplasm that recurred with a disseminated intraperitoneal low-grade mucinous epithelial neoplasm and mucinous ascites. To our knowledge, this is the first reported case of a mature teratoma-associated mucinous epithelial neoplasm from any anatomical site with documented late recurrence as pseudomyxoma peritonei.