Mucosal Schwann Cell Hamartoma of the Gall Bladder.

Mucosal Schwann cell hamartoma (M-SCH) of the intestinal mucosa is a rare entity and incidental finding in histological examination. Histological characteristics are Schwannonian cell proliferation in lamina propria with S100-positivity. M-SCH-like lesion in the gall bladder is even rarer and is a recently reported entity. We report this extremely rare lesion in a cholecystectomy specimen of a 4-year-old boy, which makes it the youngest patient to be having M-SCH-like lesion in the gall bladder. Copyright:

INTRODUCTION

Benign nerve cell tumors have been characterized in detail for superficial lesions in the body, but they are rare in the gastrointestinal tract. With the wide-scale usage of colonoscopy for the screening of colorectal pathologies, Mucosal Schwann cell hamartoma (M-SCH) have been found as a histological entity not so uncommonly in the polypoidal lesions of the colo-rectum, usually in the young- to middle-aged individuals.[1] In contrast, M-SCH like lesion in the gall bladder is extremely rare and more so in children.[2] This case report aims to highlight an extremely rare entity of the gall bladder in a young child.

CASE REPORT

A 4-year-old boy presented with symptomatic gallstone disease with a history of recurrent episodes of the right upper abdominal colicky pain for 1.5 years. On examination, the general physical examination was remarkable and so was the examination of the abdomen. An ultrasound of the abdomen was suggestive of gallstones. The liver function tests were within the normal limits, and there was no evidence of hemolytic disease. The child underwent laparoscopic cholecystectomy with a normal postoperative course. He was discharged on the postoperative day 2. The gross histopathological findings of the excised gallbladder showed 6 cm long gallbladder with a wall thickness of 0.1–0.2 cm and 2 calculi, while microscopic findings suggested thinned out gallbladder wall with marked denudation of surface epithelium and lamina propria showing increased Schwannian cells which were positive for S100 cells on immunohistochemistry (IHC) [Figure 1]. The child is on routine follow up and is currently asymptomatic after 12 months of the procedure.

Figure 1

(a) Section shows Spindle cells with buckled nucleus (arrow) in the lamina propria (H and E, ×200); (b) Nuclear positivity of S100 immunohistochemistry in the Schwannian cells (arrow) lying in the lamina propria (×400)

DISCUSSION

The M-SCH got recognition as a separate entity recently.[3] Historically, these were termed as neuroma, perineuromas, Schwannomas, and neurofibroma. These are benign neural lesions of the intestinal mucosa with no syndromic associations. The etiology of the lesion is not clear.[2] There are scattered reports of M-SCH, with most cases that have been reported, occur in the colo-rectum and stomach.[45] The M-SCH-like lesion in gallbladder specimens has been reported recently by Khanna et al., predominantly in adults and the elderly with the mean age being 25 years.[2]

Only means to detect M-SCH is by histopathological examination and subsequent IHC of suspected lesions. Preoperative detection may not be possible, as no morphological abnormalities have yet been described in the literature.[2] In the index case, also, radiologically, only a gallstone could be identified; however, no polyp was noted in gross or histopathological examination.

On microscopy, there was benign mucosal proliferation, which was composed of Schwann cells with infiltrated spindle cell lesion, which expanded the lamina propria. These spindle cells had abundant dense eosinophilic cytoplasm with elongated tapery or wavy nuclei. However, no cellular atypia, pleomorphism, or mitotic activity. No ganglion cells were noted. The lesion was mostly diffusely distributed along the specimen. These lesions extensively stained positive for S100, NSE, and CD56; however, it was negative for other neural stains such as EMA stains, CD34, CD117, smooth muscle actin, synaptophysin, and chromogranin.[12] These findings are characteristics of an M-SCH, as proposed by Gibson and Hornick.[3] Our patient had no features of neurofibromatosis1 or other hereditary diseases; therefore, we diagnosed our case as an M-SCH.

The differential diagnosis for M-SCH is perineuroma, ganglioneuroma, neurofibroma, and gastrointestinal Schwannomas. All these can be excluded histopathologically and IHC by their classical features.[4] To put this into perspective, perineuroma are positive for EMA and negative for S100, ganglion cells are present in ganglioneuroma in contrast to M-SCH, where ganglion cells are absent. Also to note neurofibroma is unlikely to involve mucosa, and they show the focal positivity of S100 in contrast to diffuse positivity in M-SCH.[2] Although proliferation of Schwann cells is observed in M-SCH, these hamartomas can be differentiated from Schwannomas with no specific findings of Verocay bodies, Antoni A and Antoni B regions, lymphoid cuffs, and lymphoid infiltrations.[1] M-SCH in other parts of gastrointestinal tracts can also be found, as enumerated earlier, but they present with polypoid mucosal lesions in addition to the histological characteristics of M-SCH.[3]

M-SCH are incidentally detected and are not associated with any clinical syndrome. The grossly insignificant presentation can be a histological surprise. An exact theory to explain the occurrence of M-SCH is elusive, but it is postulated that mechanical obstruction and chronic inflammation induce propagation of LGR5-positive stem cells of the intestinal epithelium. The plasticity of these stem cells may lead to regeneration and hypertrophy of nerve fibers in the gastrointestinal tract and also in the gall bladder, ultimately developing into an M-SCH.[26]

The significance of these lesions is still unestablished and hence, the importance of long-term follow-up, as this may unearth the natural history of these lesions in future. This very fact highlights the importance of our report, which is directed to sensitize the pediatric surgical and pathology colleagues about this rare, seemingly benign, but unknown late effects. Recurrences are not been described as yet with these lesions.

CONCLUSION

The M-SCH-like lesion of the gallbladder is a rare mucosal lesion which can be incidentally detected in pediatric gallstone disease. Both treating pediatric surgeons and pathologists must be aware of this entity to not to miss them and ignore them. A long-term follow-up is suggested, as the true significance of these lesions is still not elucidated.

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.