INTRODUCTION
The Neurenteric cyst is an infrequent lesion of the spinal axis consisting of heterotopic endodermal tissue. It is congenital abnormality of the spine characterized by the presence of mucus-secreting epithelium suggestive of the gastrointestinal tract. Holcomb and Matson, first coined the term Neurenteric cyst.[1–3] About 0.7-1.3% of all spinal cord tumors are comprised of Neurenteric cyst.[4] Approximately 90% of Neurenteric cysts are localized in the intradural/extramedullary compartment.[5] Posterior fossa and spinal cord are the favored sites. It affects all age groups. Due to their low incidence, Neurenteric cysts are majorly described in the literature as case reports and case series.
CASE HISTORY
We present a case of six-month-old female, with history of cough and intermittent fever. X-ray revealed a cystic shadow in mediastinum which was initially confused for pneumonia. Hence, she received treatment for pneumonia twice without any symptomatic relief. Non-contrast-enhancing magnetic resonance imaging (MRI) showed an extradural cyst in the posterior mediastinum, isointense on T1-weighted and hyperintense on T2 –weighted sequences, measuring 2.5 × 2 cm [Figure 1]. Intraoperatively, the cyst was located in posterior mediastinum, extradural with its bed formed by thoracic vertebral bodies [Figure 2].
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Figure 1: Non contrast enhancing MRI showing an extradural cyst in the posterior mediastinum just anterior to cervical vertebral bodies
Figure 2: Intraoperative image of Neurenteric cyst showing its relation with the esophagus and the adjacent lung
Grossly, the cyst structure measured 2.4 × 1.8 × 1.5 cm. External surface showed smooth surface with mild congestion. On opening the cyst, pale yellowish fluid oozed out and internal surface showed smooth mucinous and brownish areas. The cyst was surgically excised. Microscopically, the cyst was lined by gastric type of mucosa with muscle coat of variable thickness, focal areas of ulceration with lymphocytic infiltration forming lymphoid follicles with germinal centers [Figures 3-6]. With this typical morphology, it was diagnosed as Neuroenteric cyst type B. Following excision, her postoperative recovery was uneventful and she is disease free after two years of regular follow-up.
Figure 3: Neurenteric cyst showing cyst wall with areas of ulceration and inflammation showing hyperplastic lymphoid follicles. Muscle coat of variable thickness is also visible (H&E ×40)
Figure 4: Neurenteric cyst showing gastric type of mucosa lining the cyst wall with muscularis mucosae and a thick layer of muscularis propria (H&E ×40)
Figure 5: Cyst wall lining of Neurenteric cyst demonstrating all layers similar to normal gastric wall (H&E ×100)
Figure 6: Cyst lining details of Neurenteric cyst resembling normal gastric mucosa (H&E ×400)
DISCUSSION
Neurenteric cysts are rare congenital lesions common in the ventral part of the spinal cord in the intradural and extramedullary area of the cervical and thoracic regions.[6] It comprised heterotopic endodermal tissue resulting from failure of complete separation of the notochord and endoderm occurring in the third week of embryogenesis. Neurenteric cysts are predominant in male population and usually present in the second or third decade of life.[6] Grossly, Neurenteric cysts consist of a thick outer membrane filled with straw colored fluid. The cyst fluid may range from being “milky,” “blackish,” “CSF-like clear,” and “clear jelly.”[5,7,8]
Radiology
Patients presenting with signs or symptoms associated with Neurenteric cysts require evaluation by MRI and/or computed tomography (CT). MRI has proven superior in comparison to CT, due to its sensitivity to detect the neural component.[9–11] MRI also helps, as it rules out the confounding bony artefact, usually associated with CT scans. Regardless, CT scan still plays a significant role in the evaluation of Neurenteric cysts secondary to the bony malformations associated with this lesions.[9]
On non-contrast enhancing MRI imaging, Neurenteric cysts are isointense on T1-weighted and hyperintense on T2-weighted sequences.[12] Although these features are considered typical of Neurenteric cysts, many variations are often reported.
Surgical management
Surgical total resection remains the first line of management. However, vertebral anomalies or extensive adhesion to neuronal component suggest opting for partial resection and can cause difficulties in, complete resection resulting in recurrences and also prove hazardous.[13,14] There are three types of approaches for the resection and but the current literature lacks data for the most suitable approach: Posterior, most widely reported surgical approach is associated with few intraoperative complications,[15] Anterior approach is an effective option but is associated with damage to adjacent neurovascular structures, fusion failure, hematoma, and CSF leakage.[12,16] Lateral approach is the least commonly preferred technique and associated with vascular damage.[17,18] Aspiration of cyst fluid has been found to be associated with recurrence and is, therefore, the minimally desirable intervention.[12] According to the literature, incidences of postsurgical recurrence have ranged between 0% and 37%.
Histopathology
Classically, Neurenteric cysts are described microscopically as a central cyst lined by mucin-producing simple columnar or cuboidal ciliated/non-ciliated epithelium with goblet cells. Wilkins and Odom formed classification criteria for Neurenteric cysts, based on three histopathological features [Table 1].[19] Type A cysts comprise either columnar or cuboidal cells, with ciliated and non-ciliated components on top of a basement membrane composed of type IV collagen. Type B cysts comprised all the features of type A in addition to bone, cartilage, lymphatic tissue, adipose tissue, or glandular components. Type C cysts are composed of type A features along with ependymal/glial component. These criteria have been used to categorize the histological subtypes, but it is not related to the site, extent, or outcome after resection of the Neurenteric cyst [Table 1].[19]
Table 1: Wilkins and Odom histopathological classification system for Neurenteric cyst
[ 19 ]We conclude that neurenteric cysts are relatively uncommon, its location in the posterior mediastinum as an extradural cyst, is even rare. The spinal region being the most common location, the presenting symptoms are consistent with those related to the spinal cord and associated nerve root compression. MRI has proved to be a Gold standard investigation, however, a CT scan is helpful in detecting bony abnormalities which may co-exist with displaced remnants of the developing gastrointestinal/respiratory tract. Complete surgical excision is the treatment of choice as partial resection showed chances of reoccurrence and need timely radiological follow-up to assess re-accumulation of cyst contents.
Key messages
Neurenteric cyst should be considered in differential diagnosis of mediastinal cysts.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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