Since SCT and CS are associated with different pathological findings, this study hypothesized that their prognosis is likely to be different. Comorbidities, perioperative factors, and long-term outcomes were significantly different from those of isolated SCTs and presacral tumors in CS. This is the first study to directly compare the background and prognosis of SCT and CS.
In our study, we defined the CS group as having presacral tumors with one or both anorectal malformations and sacral dysplasia. CS with the Currarino triad of anorectal malformations, sacral abnormalities, and presacral tumors was first proposed by Currarino et al. [13] in 1981. The classification of CS was first reported by Martucciello et al. [17] in 2004. According to this classification, our CS group had complete CS in seven cases with Currarino triad and mild CS in three cases with only presacral tumors and sacral dysplasia. Therefore, this study may be regarded as a comparative study of SCT and CS. In recent years, the MNX1 gene was discovered to be responsible for CS, and there are some reports on its penetrability and phenotype diversity [18]. However, there is no clear gene responsible for SCT. Besides, presacral tumors in CS arise from incomplete separation of the endodermal and ectodermal layers during early embryonic development [13]. SCTs originate from pluripotent cells (Hensen’s node) located at the tip of the coccyx [19]. Thus, from a developmental perspective, the two tumors should be considered different.
There was no difference in the background characteristics of SCT and CS in terms of sex and perinatal factors, and the results were similar to those reported previously [20, 21]. CS is associated with some comorbid malformations, with tethered cord syndrome being especially common [22]. In this study, tethered cord syndrome was significantly more common in the CS group. Although there were no significant differences in other comorbid malformations, it was more common in the CS group with three cases of urinary system malformations and one case of body surface malformations. There was one case of neuromuscular disease in the SCT group. The fact that the time to surgery was significantly longer in the CS group may be due to later diagnoses in the CS group compared that in the SCT group. This is because the diagnosis of Altmann classification type IV tumors, such as CS, is often delayed compared to the more easily diagnosed Altmann classification types I–III SCTs. Although, there are reports of CS cases of Altmann classification type II, in this study, all CS cases were Altmann classification type II, actually [23]. Additionally, the diagnosis of CS, especially in cases of mild anorectal malformations, can be easily missed when a small sacral defect is masked by a rectum loaded with stool [22].
Early postoperative complications were significantly more common in the CS group, especially dysuria. Dysuria was transient and improved over time; however, at the time of follow-up, four of the six cases had not yet improved. The main cause is thought to be intraoperative damage to the pelvic plexus. Barakat et al. [24] reported that 15 cases of Altman classification types I–II had no urinary or defecation disorders, but 5 of 7 cases (71%) of Altman classification types III–IV had urinary disorders, soiling, or constipation [24]. However, there are reports that the complications do not change according to Altmann classification [25], and it may only be a problem when the tumor occupies the deep pelvic region. Regarding long-term outcomes, defecation disorders were significantly more common in the CS group, and dysuria was not significant, but tended to be more common in the CS group. Dewberry et al. [26] reported that compared to patients with isolated SCTs, patients with a presacral mass and anorectal malformation had worse bowel function outcomes. Additionally, it has recently been found that CS is associated with a higher occurrence of dysuria than that reported in previous studies [16]. These negative reports on the long-term outcomes of presacral tumors in CS support our findings.
Although no tumor recurrence and similar histology were observed in both groups in our study, SCT is well-known for its recurrence and malignant transformation. Dirix et al. [27] examined the malignancy and recurrence risk in SCT and presacral tumors associated with CS. Their results showed that in isolated SCTs, the malignancy and recurrence risk were significantly higher in SCT than in CS. This suggests that even if the histological types of the tumors are similar, malignancy may be more common in SCT.
CS is often associated with comorbidities, such as anorectal malformations and tethered cord syndrome. Therefore, it was not possible to make a true comparison between tumors in this study, although low-type anorectal malformations, such as anorectal stenosis and anocutaneous fistulas, are often associated with good postoperative defecation control, and in this study, all tethered cord syndrome cases underwent detethering treatment. Besides, in this study, the number of cases was limited because of the rarity of the disease and the single-institution survey. This may be caused by the absence of lower limb disorders and fewer complications in the SCT group in our study than previously reported. Similarly, with regard to long-term outcomes, the follow-up period was 10 years or less, and future large-scale research is required.