Neuroendocrine tumour arising inside a retro-rectal tailgut cyst: report of two cases and a review of the literature

Abstract

Tailgut cysts (or retro-rectal cyst-hamartomas (RCHs)) are developmental abnormalities consisting of multiloculated cysts lined by squamous, transitional or glandular epithelium which, albeit rarely, may give rise to malignant transformations. Carcinoid tumours arising in the presacral region are extremely rare and usually benign, and only a few are described in the literature. Case 1: A 63-year-old female diagnosed as having bilateral ovarian cysts underwent surgery to remove a right adnexial mass that was histopathologically diagnosed as a well-differentiated carcinoid tumour. She is currently disease free after 18 months of follow-up. Case 2: A 41-year-old-female diagnosed with hepatic metastases and a solid pelvic mass arising from a moderately differentiated neuroendocrine carcinoma is currently alive with disease after having undergone surgical removal of the mass and several medical treatments. We here describe two different clinical histories of well- and moderately differentiated neuroendocrine tumours (NETs) arising from tailgut cysts in the prerectal space together with a review of the relevant literature.

Figure 1:

Case 1. Microscopy of the resected tumour in patient 1. Well-differentiated neuroendocrine tumour arising within a tailgut cyst exhibiting a thick, fibrous wall (A) containing residual, disarrayed smooth muscle fibres (A, inset). Tumour cells showed a trabecular pattern of growth (B), diffuse immunoreactivity for synaptophysin (C) but only focal for chromogranin A (C, inset) and a low Ki-67 labelling index (less than 2%) (D).

Figure 2:

Case 2. Histological appearance of the resected tumour in patient 2. Well-differentiated neuroendocrine tumour arising within a tailgut cyst exhibiting a trabecular pattern of growth (A,B) with a residual component of disarrayed smooth muscle fibres (A, inset). Tumour cells were associated with residual glandular epithelium of tailgut cysts (B, inset) and showed faint to moderate immunoreactivity for chromogranin A (C) and a higher Ki-67 labelling index with 18% tumour cells being positive (D).