Background: Esophageal immature squamous metaplasia is poorly reported in the literature. This entity can, however, be misinterpreted as high grade dysplasia or invasive squamous cell carcinoma and hence represent a potential pitfall.
Case presentation: Histopathological examination of a superficial esoophageal lesion removed by endoscopic submucosal dissection revealed a squamous cell carcinoma associated with immature squamous cell metaplasia arising from esophageal glands. Immunohistochemical stainings allowed to distinguish malignant from metaplastic cells.
Conclusions: Immunohistochemistry for Ber-EP4 is helpful in making the distinction between esophageal squamous cell carcinoma and immature squamous metaplasia. This can avoid overstaging and overtreatment, especially in early esophageal cancer.
During the past decade, management of superficial esophageal squamous cell carcinoma (eSCC) using endoscopic submucosal dissection (ESD) and endoscopic mucosal resection (EMR) gained interest. The European Society of Gastrointestinal Endoscopy recommends ESD as the first option for superficial eSCC. EMR may be considered for lesions smaller than 10 mm if an en bloc resection can be assured .
Immature squamous metaplasia (ISM) is widely described in the cervix and represents epithelial changes from a single or multiple layers of reserve cells to an epithelium composed of three or more layers of cells with features of mature non keratinizing squamous epithelium . This condition can be difficult to distinguish from high grade dysplasia, and immunohistochemistry is helpful in this distinction . In the cervix, atypical immature metaplasia is considered as a morphological type of low grade squamous intra-epithelial lesion in regard to immunoprofile as well as outcome .
Esophageal ISM is poorly described in literature but some authors made the hypothesis that esophageal ISM should be considered as a possible site of origin of eSCC development [5, 6].
Here we report the case of an ESD specimen with eSCC associated with ISM, discuss potential pitfalls and describe histopathological and immunohistochemical findings.
A 58-year-old man was referred for management of a superficial esophageal lesion by ESD.
Macroscopic examination revealed a poorly circumscribed, erythematous, ulcerated, flattened lesion measuring 26 mm. The ESD specimen was received fixed in 10% formaldehyde and pinned out on a cork. The deep margin was inked in black and the lateral margins in green. The ESD specimen was completely embedded for microscopic analysis.
Microscopic assessment revealed poorly differentiated eSCC admixed with extensive ISM (Fig. 1). ISM was found in the lamina propria and characterized by the presence of multilayered immature squamous cells covered by columnar and mucus-secreting epithelial cells. These cells formed islets with cystic appearance (Fig. 2a). ISM seemed to originate from ducts and displayed a ductal pattern reaching the superficial epithelium (Fig. 2a). Cells exhibited slight atypia with an increased nucleocytoplasmic ratio. Some mitoses were observed but they were limited to the basal area and no atypical mitosis were noted (Fig. 2b). Immature squamous cells were positive for p63 immunostaining while mucus-secreting epithelial cells were completely negative (Fig. 2c). PAS-diastase staining emphasized presence of mucus without goblet cells (Fig. 2d).
The presence of mucus-secreting cells suggests that ISM took its origin from ducts draining esophageal glands of the lamina propria. Ber-EP4 immunostaining revealed strong and membranous positivity (Fig. 2e). These islets were not invasive and collagen IV immunostaining confirmed the preserved basal membrane surrounding the islets (Fig. 2f). Ki-67 immunostaining showed proliferating cells limited to basal and parabasal compartments (Fig. 2g).
Submucosal glands were drained by ducts lined by monolayered cuboidal or stratified epithelium (Fig. 2h). Submucosal glands contained PAS-diastase positive cells while ducts did not (Fig. 2i). The ducts were positive for p63 immunostaining (Fig. 2j).
The poorly differentiated eSCC invaded the middle third of the submucosa. Tumoural cells were arranged into solid nests and showed a high level of atypia (Fig. 3a). Neoplastic cells were diffusely positive for p63 immunostaining (Fig. 3b) and Ki-67 demonstrated proliferating cells in the majority of the malignant cells (Fig. 3c). Collagen IV immunostaining showed a disrupted basal membrane (Fig. 3d). Neoplastic cells were negative for Ber-EP4 immunostaining (Fig. 3e). Deep and lateral margins were free. The eSCC was staged pT1b according to 8th TNM classification of the UICC.
In this case a poorly differentiated eSCC was associated with florid ISM originating from esophageal gland ducts.
Two types of glands exist in the esophagus: esophageal cardiac-type glands located in the lamina propria which have a duct lined by gastric foveolar-like cells, and submucosal glands which are drained by ducts lined by a single layer of cuboidal epithelium in their proximal part but becoming stratified squamous when penetrating the muscularis mucosae and the epithelium before opening into the esophageal lumen . In our case, stratification of ductal squamous epithelium of submucosal glands was already observed in the submucosa illustrating an early step of ISM. Furthermore, we illustrated that ISM displayed a ductal pattern. ISM with overlying mucus-secreting cells was only found in the lamina propria supporting the fact that this type of ISM developed from esophageal cardiac-type glands located in the lamina propria because the duct-lining cells may extend over the stratified squamous epithelium for variable distances .
Esophageal ISM is poorly reported in literature. About three decades ago, Takubo described reserve cell hyperplasia in 24% of 110 cases of which he analyzed histologically the complete mucosa of the esophagogastric junction . Esophageal ISM could originate from stem cells that are present in esophageal glands and ducts; several studies support the notion that stem or progenitor cells within esophageal submucosal glands and/or ducts can generate both squamous and Barrett’s columnar cells . We observed diffuse positivity for Ber-EP4 immunostaining in ISM while tumoural cells as well as normal esophageal squamous epithelium were negative. In squamous epithelium of endodermal origin Ber‐EP4 could not be demonstrated in mature squamous epithelium, but was focally present in immature, metaplastic and dysplastic squamous epithelium and occasionally also in hyperplastic squamous epithelium .
Esophageal ISM should not be confounded as intraductal spread of eSCC which can occur in nearly the quart of eSCC . Intraductal spread of eSCC that extends to the submucosa should not be staged as submucosal infiltration and it has no impact on 5-year survival . Similarly, esophageal ISM should not be considered as invasive cancer and we demonstrated in our case a preserved basal membrane surrounding the islets of ISM. Being aware of this pitfall can avoid overstaging and, so, overtreatment.
Classification of esophageal ISM as preneoplastic or dysplastic lesion (as in the cervix) is at this moment difficult due to lack of data in the literature.
In conclusion, extensive description of esophageal ISM is lacking in the literature; however, this entity needs to be recognized in order to avoid misinterpretation as cancer, and Ber-EP4 immunohistochemistry is a helpful immunohistochemical staining. Furthermore, data with regard to classification of esophageal ISM as possible preneoplastic or dysplastic entity are lacking. Co-occurence of ISM with eSCC as in the present case suggests that this subject merrits further investigation.
Ethics approval/ Consent for publication : Patient signed a written informed consent upon admission to the hospital. Patients chose at admission whether to opt in or to opt out of providing consent, which affirms that physicians have the right to use patient’s surplus biological material for research. Consent has been established by the local ethics committee (ethics committee Erasme-ULB) and is in accordance with Belgian and International law (Helsinki declaration).
Availability of data and materials: not applicable.
The authors declare that they have no competing interests.
Funding : not applicable
Authors' contributions : VH and AL performed ESD technique, LV realized macroscopic examination, LV and PD carried out microscopic examination. LV, VH, AL and PD wrote the manuscript. All authors read and approved the final manuscript.