Primary retroperitoneal mature cystic teratoma with focal enteric type adenocarcinoma in a post-partum woman: report of a case with literature review.

Teratomas are characterized by containing tissue from all three germinal cell layers. Occasionally, somatic type malignancies develop within a mature cystic teratoma. We reported here a rare case of enteric type adenocarcinoma, with associated dysplastic epithelial precursor lesion, arising within a mature cystic teratoma in the retroperitoneum of a 30-year-old woman status post vaginal delivery 11 weeks earlier. The mass is 17.5 cm and cystic. A polypoid mass component measuring 4.7×4.2×2.5 cm was located inside the cystic component. Microscopically, the majority of the specimen was a mature cystic teratoma with all three germinal cell layers. The polypoid mass component was an adenocarcinoma with an adjacent dysplastic epithelial precursor lesion. The adenocarcinoma was diffusely positive for CK20 and CDX-2, and focally positive for CD7, indicating enteric differentiation. A brief review of retroperitoneal mature cystic teratomas with associated somatic type malignancy was performed.