Aspiration cytology and core biopsy of a carcinoid tumor arising in a retrorectal cyst: a case report.

Retrorectal cysts are uncommon lesions of uncertain histogenesis, and primary carcinoid tumors arising in retrorectal cysts are extremely rare. We present the case of a 52-yr-old man who had a 22-cm partially cystic, partially solid mass in the presacral space. A computed tomography-guided fine-needle aspiration of the mass was performed. The smears contained abundant keratinous debris and rare groups of tumor cells. The tumor cells were cuboidal, with slightly granular cytoplasm and centrally located nuclei with speckled chromatin and inconspicuous nucleoli. Immunocytochemical analysis revealed strong reactivity for chromogranin and keratin, and focal reactivity for synaptophysin and neuron-specific enolase. The cytological diagnosis of a carcinoid arising in a tail-gut cyst was confirmed histologically. This is the first reported case of a carcinoid arising in a retrorectal cyst diagnosed preoperatively by cytology. This diagnosis is possible in the setting of consistent clinical, radiographic, and cytological findings. Copyright 2000 Wiley-Liss, Inc.