Discussion
Tailgut cysts (TGCs), also known as retro-rectal cystic hamartoma (RCH)
or epidermoid cysts in presacral and retro-rectal space, are cystic
lesions that occur due to developmental abnormalities in the embryonic
pathways and they are the remnants of the embryonic hindgut. (1) Tailgut
cysts are very rare, have an incidence rate of 1 of 40,000–63,000
patients, and are more common in middle-aged women. (2,3)
Histologically, TGCs are multilocular cysts with squamous, mucinous,
simple, pseudostratified ciliated, or transitional lining cells or may
contain bundles of smooth muscle in the cyst’s wall. Meningeal tissue,
thyroid tissue, and glomus bodies have also been reported (4).
The clinical manifestations of TGC can range from asymptomatic to
atypical clinical symptoms because of compressive effects of mass,
including constipation, rectal filling, dyschezia, infertility, dysuria,
and abdominal pain. The infectious process like repeated urinary tract
infection, abscess, and fistula formation may also occur with symptoms
including high fever, pain, and frequent micturition. (5–11)
Differential diagnoses that should be considered for retro-rectal masses
include anal gland cyst, duplication cyst, endometriotic cyst, sacral
meningocele, or pilonidal sinus. (4)
Although FNA or other cytological biopsies have been recommended in some
older articles, tissue sampling has not been recommended in more recent
data due to the risk of the tumor spreading into the abdominal cavity,
and the role of imaging in preoperative diagnosis has become more
prominent. (12) Tissue biopsy might be considered only for patients with
high surgical risks who are not a candidate for surgery. We may have to
find out about the pathology through the biopsy in this setting. (9)
CT and MRI are required to diagnose and characterize differential
diagnosis and treatment strategies. (10,11) Malignant and benign lesions
show different characteristics on MRI examination, especially on
T2-weighted images (12). Sarkar et al. believed that radiological
examination could contribute to diagnosing cystic lesions in the
presacral space; however, the definitive diagnosis can only be achieved
by surgical exploration and histological examination (13).
Malignant transformation in TGCs can occur but are rare, and the clear
pathogenesis remains unknown. The most frequent histological types
include adenocarcinoma and neuroendocrine tumors. Others include
carcinoid tumors, squamous cell carcinoma, endometrioid carcinoma,
adenosquamous carcinoma, transitional cell carcinoma, and sarcoma were
rarely reported (5,9,14). Squamous cell carcinoma was previously
reported in just four reports (15–17), and our case was the fifth.
Generally, the reported incidence rate of malignant tumors arising from
epidermoid cysts is 0.011 % –2.2 % (6,7). However, a higher rate of
malignant transformation has been reported in some reviews of TGCs. Feng
Liang et al. have mentioned in a review article that about 30 % of
reported cases of TGCs in the literature were malignant. (8) It could be
probably due to the higher chance of developing symptoms in these
malignant cases. Therefore they are more likely to be diagnosed.
Similarly, K. Nicoll et al. have also reported that the overall rate of
neoplastic transformation was 26.6% and noted the low metastatic rate
in these malignancies. (18) We have found only 2 cases of metastasis in
the literature review which were SCC and NET. (15,19)
The treatment of choice for all TGCs is complete surgical excision.
Additional chemotherapy or radiation therapy treatments are given if
malignancy is detected based on the pathology report. The minimally
invasive transanal or transrectal approach is indicated for small
low-lying, non-infected cases because of the risk of pelvic infection in
these surgical approaches (20). A transabdominal surgery approach is
preferred in patients with suspected malignancy because of better access
and visualization for a complete oncological surgery(20).
In the case of pre-rectal cysts, of which Tailgut cysts can be one, the
possibility of malignant transformation should be considered, and in
this case, surgical resection and complete evacuation of the cyst with a
suitable margins may be the best measure for potential diagnosis and
treatment of these lesions. In our case, complete oncological surgery
was not performed, leading to early disease progression and metastasis
despite chemo-radiation therapy. This case highlights the critical role
of extensive surgery, and if it is not expected to be possible,
neoadjuvant treatments may facilitate this goal. If surgery is done
first, it would be logical to consider adjuvant therapies. Eventually,
there is no conclusive guideline or standard policy on adjuvant
treatment indications in malignant tailgut cysts. Further research is
needed, so treating such patients in a multidisciplinary team is
reasonable.