A retroperitoneal bronchogenic cyst with malignant change

A unique case of adenocarcinoma arising in a retroperitoneal bronchogenic c yst is presented. A 55-year-old woman presented with lower abdominal discom fort. Computed tomography revealed a retroperitoneal cystic mass attached t o the ascending colon. The resected cyst was unilocular and filled with mil ky white mucus and hemorrhagic debris. Histologically, most of the cyst wal l was of well-differentiated papillary adenocarcinoma with no cyst wall inv asion. Other small areas of the cyst were lined with variably atypical dysp lastic/metaplastic cuboidal to pseudostratified columnar epithelium. The cy st wall was mostly hyalinized, but there was apparent thickened subepitheli al basement membrane, elastosis, and a single layer of smooth muscle that s uggested bronchial wall structures. A mucin staining study with O-acylated sialic acid, which is used for the demonstration of gastrointestinal, chole cystic and uterine cervical mucins, was negative for the mucin-producing ep ithelial cells of the cyst, Thus, to our knowledge, this is the first repor ted case of adenocarcinoma arising in a retroperitoneal bronchogenic cyst.