Tail gut cyst adenocarcinoma: A rare entity diagnosed on cytology

Tailgut cyst is a rare benign cystic lesion believed to originate from small portions of the embryonic tailgut, which normally disappear in early foetal development. It is often misdiagnosed due to the general unawareness with this entity and also because of its clinical presentation similar to other common diseases such as perianal fistulas or abscesses. We take this opportunity to report a case of tailgut cyst in a 33-year-old Indian male. The patient had presented with painful swelling in sacral region, which had been gradually increasing in size. The case was diagnosed by fine needle aspiration cytology (FNAC) as adenocarcinoma arising in tailgut cyst and later confirmed by histopathology. Tailgut cysts are congenital cystic hamartomatous lesions, which occur very rarely. They are generally benign, but malignant change or transformation in it has also been reported, which is even rarer in occurrence. FNAC is an effective diagnostic tool, which if applied appropriately can be used for the early detection of these lesions and also malignant transformation of tailgut cyst.