Acquired Esophageal Strictures in Children: Morphometric and Immunohistochemical Analyses

Abstract

Background:

Esophageal strictures (ES) in children are not well characterized pathologically. We report unique histopathologic analyses of resected acquired ES and control esophagi (CE).

Methods:

Muscle layer thicknesses were measured in intact well-oriented areas; inflammatory cells were counted in the most inflamed high power field (hpf). Sections were stained with relevant antibodies. Results were expressed as median, lower and upper quartiles. Wilcoxon Rank Sums non-parametric test was used to compare groups; P ≤ 0.05 was considered significant.

Results:

All ES (N = 10) showed focal replacement of lamina propria, muscularis mucosa and submucosa by actin+ fibers emanating from muscularis propria. Compared to CE (N = 8), ES displayed significantly thickened muscularis mucosa and propria, and increased mast cells (tryptase- and chymase-positive), and eosinophils in muscle layers (all P ≤ 0.01). Matrix proteins periostin and fibronectin were identified in the muscle layers of CE, and in the extracellular matrix in areas of disrupted architecture in ES.

Conclusions:

Compared to CE, acquired ES in children show significant structural alterations, including obliterative muscularization, inflammatory cell mural infiltrates, and extracellular matrix protein deposits. Therapies targeting connective tissue expansion, mast cells, eosinophils and inflammation may be beneficial to treat ES.

Introduction

Esophageal strictures (ES) in children cause significant morbidity, including poor nutrition and growth retardation, and may require repeated endoscopic dilations or surgical resection to relieve obstruction.¹ Caustic injury, gastroesophageal reflux disease (GERD) or eosinophilic esophagitis (EoE) are common causes of ES.^2,3 Ingestion of caustic substances affects several hundred children in the U. S. annually with an annual related health care expenditure of approximately twenty million dollars.⁴ EoE is a chronic antigen-driven disease characterized by eosinophil-rich inflammation that may be transmural. EoE-related strictures in children may occur anywhere in the esophagus but are most common distally.³ The few available reports of ES resected from adult EoE patients describe numerous eosinophils and mast cells in the esophageal wall,^5–10 and marked muscularis propria hypertrophy simulating a neoplasm.⁷

Greater knowledge of the structural components of acquired ES could aid efforts both to reduce their formation, and to develop effective medical therapies for existing ES.^11,12 We report our structural analyses of acquired ES in children, and compare the findings to transmural necropsy samples of normal esophagi.

Materials and Methods

This study was approved by the Institutional Review Board at Cincinnati Children’s Hospital Medical Center. The surgical pathology database, containing records of pathology specimens from 1968 to the present, was searched for the diagnosis esophageal stricture through April 30, 2013. Only acquired strictures with intact transmural circumferential esophageal resections were included; segmental or piece-meal resections were excluded. Cases in which an ES followed a surgical repair of a congenital anomaly were included. Autopsy controls were age-matched to the ES cases, had the customary longitudinal sample for microscopic examination taken from the esophagus at the esophagogastric junction, and had normal gross and microscopic esophageal appearances described in the final autopsy report. Sections of all specimens were fixed in 10% formalin, routinely processed and embedded in paraffin. Slides stained with hematoxylin and eosin (H&E) of cases and controls were reviewed and a representative paraffin block was selected for histochemical and immunohistochemical stains (Supplementary Table 1). Muscularis mucosa and propria thicknesses were measured on H&E-stained slides at 40× using an eyepiece micrometer containing a linear scale that measured 2.4 mm in length. In all esophagi, maximum muscle layer thickness was measured in a well-oriented area in which identifiable muscle layers displayed distinct margins and there was overlying squamous epithelium. In order to compare results obtained from ES to those from the control esophagi (CE), extravascular inflammatory cells were counted in layers that were identified in both ES and control samples; inflammatory cells in areas of disrupted architecture in ES were not counted because those counts did not have corresponding normal values. Peak number of inflammatory cells (eosinophils assessed on H&E-stained slides slides, and mast cells assessed on slides stained with tryptase or chymase antibodies) was obtained by counting cells in the most inflamed area of each layer of the esophageal wall at 400× magnification (0.3 mm²). Results were expressed as median, lower and upper quartiles. Wilcoxon Rank Sums non-parametric test was used to compare groups and P ≤ 0.05 was considered significant. Clinical information was obtained from chart review.

Results

Twenty-five specimens with a diagnosis of ES included 15 unsuitable for the study because they consisted of slides reviewed in consultation without paraffin blocks (1); a specimen from a patient with a genetic predisposition to esophageal stricture (epidermolysis bullosa-1); mucosal biopsies only (3, 1 with a diagnosis of esophageal web); or disrupted pieces of esophageal wall (10, 5 from previously repaired tracheoesophageal fistulas, 1 following chemical ingestion, and 4 with strictures of unknown causes). The remaining 10 cases were used for the study. At the time the samples were collected, the median age (years) of subjects in the CE group (N = 8; 4 males, 4 females) did not markedly differ from the ES group (N = 10; 6 males, 4 females; 2.5 (0.5–4.9) vs 3.7 (2.5–12.5), P = 0.2) (Table 1). However, 4 subjects in the ES group and only 1 in the CE group were over the age of 9 years. Diagnoses in the CE subjects included congenital anomalies/syndromes (4/8), central nervous system abnormalities (3/8), and infection (1/8). Causes of ES were ingestion of a caustic substance (5/10; mean time interval from ingestion to stricture resection 9 ± 2.6 months), stricture following surgical repair of congenital esophageal anomaly (3/10), and GERD (2/10; one (Table 1, #18) stricture followed surgical repair of an esophageal perforation of unclear etiology in infancy). One patient (Table 1, #10) with an unspecified congenital anomaly repaired at an outside hospital had EoE following the esophageal repair. All strictures were refractory to dilation.

Table 1.

Demographics and Diagnoses.

	Age (years)/Sex	Diagnosis	Time (years) from injury to resection
#1 Control	0.5 / M	Trisomy 21; CHD; S/P Nissen	N/A
#2 Control	14.3 / M	Influenza B; Staphylococcus pneumonia	N/A
#3 Control	0.5 / F	Leukoencephalopathy; NG feeds	N/A
#4 Control	2.6 / M	CP; acute bronchitis/pneumonia	N/A
#5 Control	0.7 / F	CHD; chronic lung disease; gastrostomy	N/A
#6 Control	5.3 / M	Encephalopathy; GER; gastrostomy	N/A
#7 Control	2.4 / F	CDLS; CHD; GERD; gastrostomy	N/A
#8 Control	3.8 / F	CHD	N/A
#9 Stricture	9.9 / M	Caustic ingestion	0.58
#10 Stricture	3.6 / M	Perianastomotic stricture; S/P repair of congenital esophageal anomaly; asthma; EoE	3.58
#11 Stricture	12.2 / F	Caustic ingestion	0.92
#12 Stricture	18.3 / M	GERD; Barrett esophagus; Noonan syndrome	1
#13 Stricture	3.2 / F	Caustic ingestion	1
#14 Stricture	2.3 / M	Caustic ingestion	0.83
#15 Stricture	3.8 / F	Caustic ingestion	0.5
#16 Stricture	2.5 / M	Perianastomotic stricture; S/P TEF repair	2.5
#17 Stricture	0.9 / M	Peristomal stricture; esophageal atresia; S/P esophagogastrostomy	0.83
#18 Stricture	13.4/ F	GERD; S/P resection of stricture following repair of neonatal (? iatrogenic) esophageal perforation	12.75

CHD, congenital heart disease; S/P, status post; NG, nasogastric; CP, cerebral palsy; GER, gastroesphageal reflux; CDLS, Cornelia de Lange syndrome; GERD, Gastroesophageal reflux disease.

Endoscopic Esophageal Appearances

Available archived videos of esophageal endoscopies of one CE patient (Table 1, #6) were normal. Archived videos of ES patients showed erythema, edema, furrowing and cobblestoning above a distal esophageal stricture (Table 1, #10), and mild edema and furrowing distal to a midesophageal stricture (Table 1, #9).

Gross Appearances of Resected Strictures

The length of the resected specimens varied from 1.5 to 7.7 cm. On gross examination 7 of the strictures exhibited thick walls in the area of the stricture, sometimes with loss of normal mural markings. A protruding mass of white tissue compromising the esophageal lumen was described in one stricture (Table 1, #17). The mucosa was red and rough, marked by irregular folds, or normal. Stomas or anastomotic sites were not described grossly in any of the specimens.

Microscopic Appearances

All ES displayed squamous epithelium. Strictures from subjects with GERD also displayed mucosa consistent with Barrett mucosa (Table 1, #12 and #18). Mucosal erosion or ulcer was seen in sections of six ES, and focal necrosis in two additional ES. Basal zone hyperplasia was seen in all ES and intercellular spaces were dilated in seven cases. In areas of intact architecture, the lamina propria showed varying amounts of chronic inflammation in all cases, fibrosis in 5 cases, and abscesses in 2 cases. The submucosa showed chronic inflammation in 6 cases and fibrosis in 3 cases. Foreign body granulomas or foreign body giant cells, consistent with preoperative steroid injection sites, were found in 5 cases.

Muscle Layers Were Markedly Thickened and Altered in ES

In areas of intact architecture, endogenous smooth muscle layers were significantly thickened in ES compared to CE (Table 2, Figure 1(A) to (C)). More remarkably, in all strictures, normal architecture was focally replaced by elongated and spindled cells that replaced lamina propria, muscularis mucosa and submucosa. Many of the fibers in those areas appeared in H&E stains to be smooth muscle fibers continuous with residual muscularis propria (Figure 1(C)). The areas that lacked normal landmarks between epithelium and muscularis propria, and contained fibers consistent with smooth muscle, resembled submucosal obliterative muscularization described in small bowel Crohn disease strictures.¹³

Table 2.

Morphometric Data.

	Control esophagia	Esophageal stricturesa	P value
Muscularis mucosa thickness (mm)	0.2 (0.1–0.3)	1.2 (0.7–1.5) (N = 7)	P = 0.002
Muscularis propria thickness (mm)	1.2 (0.9–1.7)	3.1 (2.7–4.4)	P < 0.001
Peak count tryptase + cells in epithelium	5.5 (4.3–11.8)	3 (0–13)	P > 0.2
Peak count tryptase + cells in lamina propria	10 (6.8–22.5)	8.5 (5.3–18.5)	P > 0.5
Peak count tryptase + cells in muscularis mucosa	11 (7–12.8)	17 (13–26.5) (N = 9)	P = 0.01
Peak count tryptase + cells in submucosa	12 (9.5–17)	16.5 (6–21.3) (N = 6)	P > 0.7
Peak count tryptase + cells in muscularis propria	4.5 (4–8.3)	40.5 (31–55.8)	P < 0.001
Peak count tryptase + cells in myenteric plexus	0.5 (0–2)	6 (2.8–7.3)	P = 0.002
Peak count chymase + cells in epithelium	2 (1–3)	6.3 (2–7.9)	P > 0.8
Peak count chymase + cells in lamina propria	10.5 (6–18.8)	8 (4.3–9.8) (N = 8)	P = 0.4
Peak count chymase + cells in muscularis mucosa	9 (5.5–10)	13 (9–18) (N = 7)	P > 0.2
Peak count chymase + cells in submucosa	14 (9–20.3)	21 (10–30) (N = 6)	P = 0.5
Peak count chymase + cells in muscularis propria	4.5 (2.5–13.3)	34 (23.5–49.5)	P < 0.001
Peak count chymase + cells in myenteric plexus	1 (1–2)	2 (1–6) (N = 9)	P > 0.2
Peak eosinophil count in epithelium	0 (0–0)	1 (0–6)	P = 0.013
Peak eosinophil count in lamina propria	0 (0–1.5)	3 (0–7) (N = 9)	P = 0.06
Peak eosinophil count in muscularis mucosa	0 (0–3.8)	2 (0–4.5) (N = 9)	P > 0.4
Peak eosinophil count in submucosa	0 (0–0)	1 (0–25.8)	P = 0.028
Peak eosinophil count in muscularis propria	0 (0–0)	11.5 (1.5–39.5)	P = 0.002
Peak eosinophil count in myenteric plexus	0 (0–0)	1 (0–2.3)	P < 0.013

Median (lower, upper quartile).

^aN = 8 for all control esophagi measurements, and N = 10 for esophageal strictures measurements unless otherwise indicated. All peak counts are per high power field (0.3 mm²).

Figure 1.

A, In this CE, squamous epithelium lines the surface at top, lamina propria resides beneath the epithelium, muscularis mucosa (white bar) is beneath the lamina propria, submucosa is beneath muscularis mucosa, and muscularis propria (black bar) is the outermost layer, covered externally by adventitia (except for the intraabdominal esophagus that is invested in serosa). 40×. B, In contrast, the wall of this ES does not show distinct layers except for squamous epithelium and muscularis propria (black bar). The tissue between the epithelium and the muscularis propria is composed largely of fibers resembling smooth muscle fibers. The wall is exceedingly thickened and half the magnification of Supplementary Figure 1A is required to include the entire wall. 20×. C, A closer view of another area of this ES shows squamous epithelium at the top (black arrow), and the inner edge of the muscularis propria at the bottom of the photo (black edge arrows). The lamina propria, muscularis mucosa and submucosa are not distinguishable, and are replaced by fibers, some of which appear continuous with the muscularis propria (black edge arrows at bottom right). 40×.

Immunophenotyping Identified Smooth Muscle Fibers and Myofibroblasts in Altered Areas in ES

Among actin isotypes, alpha actin is normally expressed in gastrointestinal muscle and blood vessel walls, and gamma actin is expressed in gastrointestinal muscle and to a lesser degree in blood vessel walls. In CE, smooth muscle layers stained with antibodies to alpha and gamma actin isoforms, but not with antibody to vimentin (Figure 2(A), (C) and (E)), a staining pattern that was retained in intact muscle layers in ES. In the foci of obliterated architecture, fibers that appeared on H&E stains to be smooth muscle fibers expressed the immunophenotype of normal esophageal wall muscle layers (alpha actin+, gamma actin+, vimentin−) (Figure 2(B), (D), and (F)). In addition to those fibers, thinner fibers expressed the immunophenotype characteristic of myofibroblasts (alpha actin+, gamma actin−, vimentin+). This staining pattern is consistent with that reported in obliterative muscularization in Crohn disease strictures.¹⁴

Figure 2.

A, Alpha actin antibody decorates the muscularis mucosa and muscularis propria in this CE. Blood vessels walls (arrows) also stain with the antibody. 40×. B, In this first of several serial sections of an area of the ES in Figure 1, nodules of fibers that replace the lamina propria, muscularis mucosa and submucosa stain with antibody to alpha actin (black arrow). Blood vessel walls also stain (white edge arrows). 40×. C, Gamma actin antibody decorates muscularis mucosa and muscularis propria in this CE. Unlike the vascular staining with alpha actin antibody, some blood vessels (arrows) do not stain with the antibody. The inset (100×) illustrates the characteristic globular staining pattern of gamma actin antibody. 40×. D, In ES, some of the fibers stain with antibody to gamma actin (black arrows), and vascular wall fibers do not (white edge arrows). 40×. E, Vimentin antibody does not stain smooth muscle fibers in either the muscularis mucosa or propria but stains thin fibers (inset, 100×) representing fibroblasts in CE. 40×. F, In ES, vimentin antibody stains mainly thin fibers with variable intensity (black arrows) and as well as blood vessel walls (white edge arrows). 40×.

Trichrome stain demonstrated structural collagen in CE and ES, and in addition stained abnormal fibers in altered areas in ES (Supplementary Figure 1A, B, respectively).

Extracellular Matrix Proteins Were Expressed in Acquired ES

Extracellular matrix is vital for tissue form and function and plays a critical role during wound repair.¹⁵ We interrogated the extracellular matrix for components expressed by esophageal connective tissue in vitro, specifically periostin and fibronectin, which perform multiple functions in extracellular matrix. Antibody to periostin and antibody to fibronectin demonstrated the proteins mostly in muscular layers in CE (Figure 3(A) and (C)) but decorated the extracellular matrix in areas showing obliterative muscularization (Figure 3(B) and (D in ES)). In addition, in CE interleukin (IL)-13 and transforming growth factor beta (TGFb), known upregulators of periostin and fibronectin secretion in vitro, were detected sparsely in cells mainly in the inner layers of the esophageal wall (Figure 3(E) and (G)), but more abundantly in cells in ES (Figure 3(F) and (H)) in areas of architectural disruption.

Figure 3.

A, Periostin antibody stains muscularis mucosa and propria and blood vessel walls in this CE. 40×. B, Periostin is present in this area of smooth muscle and myofibroblast proliferation in ES (arrows). 40×. C, Fibronectin antibody decorates the muscularis mucosa and propria of this CE with varying intensity. 40×. D, Fibronectin is present in the same area as periostin in this ES. 40×. E, Antibody to IL-13 decorates cells mostly in the inner layers of the CE wall. 40×. F, In a different ES, cells stain with antibody to IL-13 (arrows). 40×. G, Antibody to TGFb shows a pattern similar to IL-13 in CE, and stained cells had granular cytoplasm (inset, 400×). 40×. H, TGFb antibody also stained cells in ES, and as with IL-13 the cells had granular cytoplasm seen in this high power view (400×), suggestive of mast cells (arrows). I, Tryptase (L) and chymase (R) antibodies decorate mast cells mainly in the inner layers of the CE. (L: 40×; R: 100×). J, Numerous mast cells are detected with tryptase antibody (L, arrows) and with chymase antibody (R, arrows) in the residual muscularis propria of this ES.

ES Displayed Increased Inflammatory Cells

Tryptase and chymase are proteases released from mast cell granules; all mast cells stain with tryptase antibody, and chymase antibody identifies mast cells that typically reside in connective tissue. Tryptase and chymase antibodies decorated mast cells in all layers of the walls of CE and ES (Figure 3(I) left, right). However, mast cells in ES appeared more concentrated in the muscularis propria compared to inner layers, a gradient opposite that observed in CE (Table 2, Figure 3(J) left, right). Compared to CE, in ES, tryptase+ mast cells were significantly increased in both muscularis mucosa and propria, and chymase+ mast cells were increased in muscularis propria. Although not abundant, both tryptase + mast cells and eosinophils were significantly increased in the myenteric plexus of ES compared to CE. Overall, mast cells appeared more plentiful than eosinophils in both CE and ES. Eosinophil infiltrates were found in all ES and were most numerous in muscularis propria (Table 2, Figure 4). In contrast, few scattered eosinophils (≤7 per high power field) were found in the muscularis mucosa and/or lamina propria in only 2 CE, and were not seen in CE submucosa or muscularis propria.

Figure 4.

This box and whiskers plot shows the number of mast cells and eosinophils found in the layers of the wall of the esophagi in CE and ES. *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001.

Discussion

Muscle Abnormalities Are Prominent in ES

Acquired ES in children exhibited marked architectural abnormalities, including significantly thickened muscularis mucosa and muscularis propria, prominent extracellular matrix, and areas of obliterative muscularization comprised of smooth muscle fibers and myofibroblasts. Inflammation was another abnormal feature, with increased mast cells and eosinophils in the muscle layers in ES compared to CE. These data implicate both fibromuscular tissue and inflammatory cells as important in the generation and maintenance of ES. Further larger studies are required to more firmly establish normative data for esophageal stricture in children and adolescents.

We found areas of architectural disruption in ES, enriched with smooth muscle fibers that appeared to be continuous with the muscularis propria and that possessed the immunophenotype of normal esophageal smooth muscle, expressing alpha and gamma isoforms of smooth muscle actin. Similarly, muscle proliferation referred to as obliterative muscularization of the submucosa was reported in a study of small bowel strictures in patients with Crohn disease who had a history of obstruction but not prior surgical resection; alpha smooth muscle actin-positive muscle spanned the wall from the base of the mucosa to the muscularis propria replacing normal structures.^13,14 The similarities between small bowel and ES suggest that mechanisms common to stricture formation may exist throughout the GI tract, which are independent of stricture etiology.

In areas of esophageal obliterative muscularization of the submucosa, lamina propria, muscularis mucosa or submucosa were not present. For some strictures, the injury associated with caustic ingestion likely obliterated these structures, suggesting they are not necessary for stricture formation or maintenance. Also, since those structures are absent from areas of obliterative muscularization, endoscopic esophageal biopsies containing tissue deep to the epithelium could demonstrate pathologic alterations that suggest the diagnosis of stricture.

Esophageal Connective Tissue Secretes Components of the Extracellular Matrix

Extracellular matrix modulates multiple functions of tissue injury and repair including cell adhesion, communication and differentiation, and fibroblasts and smooth muscle are particularly active secretors of components of intercellular extracellular matrix.¹⁶ Periostin is a matricellular protein that performs numerous activities following tissue injury including facilitating cell migration¹⁵ and myofibroblast differentiation.^15,17 The abnormal architecture in ES suggests extension and/or migration of smooth muscle fibers from muscularis propria, and includes myofibroblasts. Periostin may have contributed to these phenomena in ES we studied. In vitro, primary stimulated esophageal fibroblasts produce periostin¹⁸ and therefore may have been the source of the extracellular periostin identified in areas of abnormal architecture in ES in our study. We demonstrated periostin in esophageal muscularis mucosa, as has been done previously (https://images.proteinatlas.org/12306/29397_B_4_1.jpg); we also demonstrated periostin in esophageal muscularis propria. Esophageal smooth muscle therefore may have been a source in addition to fibroblasts for matricellular periostin, as well as cofacilitator with esophageal fibroblasts of myofibroblast differentiation.

We also detected another component of extracellular matrix, fibronectin, in smooth muscle in CE and ES. Fibronectin facilitates cell adhesion and migration.^19,20 Both primary esophageal fibroblasts and smooth muscle cells secrete fibronectin at baseline culture conditions and increase secretion following stimulation.^21,22 Fibronectin and periostin were detected immunohistochemically in visceral smooth muscle but not normal submucosa in CE, but were markedly reduced or absent in visceral smooth muscle in ES (not shown), consistent with ES smooth muscle having secreted them into the extracellular matrix in the architecturally altered areas in ES. Fibronectin was identified in the extracellular matrix of ES in addition to periostin, and esophageal fibroblasts and smooth muscle cells could have been sources.

Periostin and fibronectin positively interact in the extracellular matrix: periostin binds directly to fibronectin and promotes eosinophil binding to fibronectin.^15,18 That binding may further increase fibronectin secretion: in vitro, primary esophageal fibroblasts and smooth muscle cells co-cultured with eosinophils or exposed to eosinophil products increase fibronectin secretion.^21,22

Accumulation of Esophageal Mast Cells, Eosinophils and Pro-Inflammatory Cytokines

Mast cells were significantly increased in endogenous muscle layers in ES. Experimental evidence links mast cells to smooth muscle proliferation and contractility. In experimental models of EoE, mast cells increase muscle proliferation following antigen challenge;²³ prominent MIB1 staining of muscle fibers in the acquired ES in this study is consistent with increased proliferation (Supplementary Figure 1 C, D) and may have been a consequence of increased mast cell activity. Increased numbers of TGFb-expressing mast cells occur in the muscularis mucosa of endoscopic esophageal biopsies of children who have EoE,²⁴ and TGFb increases contractility of primary human esophageal smooth muscle cells in culture.²⁴ TGFb also mediates the increased secretion of fibronectin by primary esophageal fibroblasts or smooth muscle cells co-cultured with eosinophils or eosinophil products.^18,21,22 Secretion of TGFb may have increased muscle cell contractility and fibronectin secretion in the ES in this study since it was detected immunohistochemically in cells consistent with mast cells.

Another cytokine, IL-13, was detected immunohistochemically in cells consistent with mast cells, and IL-13 is one of the master regulators of eosinophilic esophagitis which is associated with ES in some patients. IL-13 stimulation increases periostin secretion from primary esophageal fibroblasts.¹⁸ Mast cells in ES expressed TGFb and IL-13 and therefore potentially contributed to multiple pathologic features seen in ES. Comparing stricture formation in several different experimental mouse models of EoE indicates that both eosinophils and mast cells contribute to stricture pathogenesis: mast cells may be important for stricture maintenance and the development of dysmotility, and eosinophils for the formation but not maintenance of stricture.²⁵

Implications for ES Treatment

The presence of potentially pathogenic inflammatory cells in strictures suggests that corticosteroid administration following caustic ingestion in pediatric patients may be beneficial,^2,11 and a randomized trial including methylprednisolone to treat pediatric patients with grade IIb esophageal burns following ingestion of corrosive substances resulted in fewer strictures among children treated with the steroid compared to those not treated.²⁶ In children with impassable strictures due to caustic ingestion, four-quadrant injection of corticosteroid permitted passage of an endoscope in most patients two weeks following injection.²⁷ The presence of fibromuscular tissue in the areas of architectural disruption in the strictures suggest that reduction of fibrous tissue might be beneficial. Topical administration of mitomycin C, which has antifibroblastic activity, to long refractory strictures in children following ingestion of caustic substances resulted in greater resolution of dysphagia and reduced numbers of dilations compared to untreated children.²⁸ However there may be long-term oncologic consequences including malignant tumor formation of the use of mitomycin C due to DNA damage;² this is especially concerning since microRNAs related to esophageal tumors were detected in esophageal mucosa samples from children with caustic strictures consistent with increased risk for esophageal carcinoma²⁹ and mild squamous dysplasia is detected, rarely, in mucosal biopsies of children with corrosive strictures.³⁰ Alternative therapies, without known potential for oncology consequences, such as those disrupting TGFb and IL-13 pathways, may be preferred. A recent study of adults presenting with EoE and severe ES showed that achieving histologic remission (<15 eosinophils/high power field) was associated with stricture improvement³¹, potentially avoiding stricture resection, and supporting the concept that anti-inflammatory therapy is an important component of therapy for ES in patients who have EoE, and possibly other causes.

In conclusion, we demonstrate significant fibromuscular alterations in ES that obliterate normal architecture, significant thickening and inflammation in residual normally-present muscle layers, and immunohistochemical evidence that connective tissue and inflammatory cells are potentially sources of important regulators of ES formation. These data suggest pathways that may be important in ES pathogenesis and therefore important targets to disrupt ES.