Retrorectal cystic hamartoma: report of 5 cases with malignancy arising in 2.

BACKGROUND Retrorectal cystic hamartomas, or tailgut cysts, are rare congenital lesions that typically present as presacral masses. These lesions are frequently clinically unrecognized and misdiagnosed. Malignant change is extremely rare. Only 10 additional cases with associated malignancy were recovered from the literature. We describe the clinicopathologic features of 5 cases, including 2 cases with malignant transformation. RESULTS All patients were women (age range, 36-69 years). The most common symptoms were pain with defecation and rectal bleeding. One patient was asymptomatic. All lesions presented as multicystic presacral masses and all were surgically resected. The lesions varied in size from approximately 2 to 12 cm (average, 9.5 cm) and overall had similar histology composed of a variety of epithelial linings (stratified squamous, transitional, and simple or ciliated pseudostratified columnar). Skin adnexa, neural elements, and heterologous mesenchymal tissue, discriminators between retrorectal cystic hamartoma and teratoma, were not identified. Arising in association with the cysts was a focus of adenocarcinoma in one case and a neuroendocrine carcinoma in another. CONCLUSIONS The clinical diagnoses in our cases were often delayed, which in part may be due to unfamiliarity with this entity. The main diagnostic difficulty is distinction from presacral mature cystic teratomas and rectal duplication cysts. Tailgut cysts require complete surgical excisions to prevent future recurrences and to preclude possible malignant transformation. Meticulous gross examination and adequate sampling are important to document the exact nature of these cysts and to rule out possible coexisting malignancies, which may be focal.