Epithelial islands associated with mandibular nerves. Report of two cases in the walls of mandibular cysts

The juxta-oral organ of Chievitz (organum yuxtaorale) updated: Embryology, anatomy, function and pathology

BACKGROUND

The Chievitz's organ or juxta-oral organ is a mysterious bilateral structure, phylogenetically preserved, which develops from the mouth epithelium as an invagination that loses connection to it in the prenatal period. It is located laterally to the walls of the oral cavity in an imprecise anatomical location and receives abundant innervation from the buccal nerve. Structurally it consists of non-keratinizing squamous-like neuroepithelial cells surrounded by two layers of connective tissue with nerve fibers and different morphotypes of sensory corpuscles. Its function is completely unknown although based on its rich innervation it is assumed that works as a mechanoreceptor.

METHODS

We have performed immunohistochemistry for axonal and Schwann cells, and the putative mechanoproteins ASIC2, TRPV4 and Piezo2 in sections of fetal juxta-oral organ.

RESULTS

Intraparenchymatous nerve fibers and sensory corpuscles were observed as well as immunoreactivity for Piezo2 in both nerve fibers and epithelial parenchymatous cells.

CONCLUSIONS

We add indirect evidence that the juxtaoral organ is a mechanoreceptor because in addition to its dense innervation, the epithelial cells and sensory nerve fibers display immunoreactivity for the mechanogated ion channel Piezo2. Based on current knowledge, the functional and clinical importance of the juxta-oral organ should be further investigated.

Perineural Pseudoinvasion: An Unusual Phenomenon in Nonmalignancies

Perineural invasion (PNI) is characterized as tumoral or nontumoral cells invading in or around the nerves. The neural invasion is considered as a histopathologic characteristic for malignancy and is considered a mechanism for its spread. Both of these patterns usually portend a poor prognosis and very often are markers to prompt additional treatment. There are also some nonmalignancies representing PNI, including benign neoplasms, mimicking lesions, and disorders, such as chronic pancreatitis and endometriosis. The previously recommended terms are PNI, spread, or infiltration. To distinguish PNI in malignancies from that in nonmalignancies, we propose the term "perineural pseudoinvasion" to convey their nonmalignant behavior. Despite the low prevalence, awareness of this benign pseudoinvasion is necessary to avoid aggressive treatment and its misdiagnosis with malignancies. We conducted a systematic search in PubMed and Scopus databases up to December 2015 to find articles reporting PNI in nonmalignancies. After screening, 63 articles were identified as relevant. There were also 2 review articles discussing PNI in nonmalignancies. We aim to present an overview of the perineural pseudoinvasion and to discuss the previously published review articles.

Pitfalls and procedures in the histopathological diagnosis of oral and oropharyngeal squamous cell carcinoma and a review of the role of pathology in prognosis

Histopathological assessment of formalin-fixed biopsy tissue and surgical resection specimens remains the cornerstone of cancer diagnosis and pathological staging in routine clinical practice. In recent years, standard protocols for reporting head and neck cancer have been widely used and these have improved the general level of the pathological assessment. In this article, we look beyond the standard protocols and deal with potential difficulties and pitfalls in the assessment of incisional biopsy specimens, surgical resection specimens and neck dissections. We draw attention to possible shortcomings and issues requiring clarification. Emphasis is given to precise histopathological definitions, histopathological detection and differential diagnosis. The approach is a practical one--a consideration of common experiences and dilemmas faced by the reporting pathologist, and where possible, we offer guidance and practical tips. The article concludes with a brief consideration of the prognostic value of accurate histopathological staging.

Morphogenesis of the juxtaoral organ in humans

The juxtaoral organ was studied using light microscopy in 55 human embryos and 90 fetuses at different stages of development. The juxtaoral organ arises from the epithelium at the bottom of the transverse opening of the primitive mouth during O'Rahilly stage 16 and becomes detached from the epithelium after O'Rahilly stage 18. The juxtaoral organ is innervated by the buccal nerve from O'Rahilly stage 20 onward, and its connective tissue capsule is clearly visible after week 11 of development. This study enabled us to describe three main periods of juxtaoral organ development: (1) the period of epithelial condensation and invagination, at O'Rahilly stages 16-17; (2) the period during which the juxtaoral organ becomes detached from the oral epithelium and is innervated, at O'Rahilly stages 18-23; and (3) the period during which the connective tissue capsule is formed, after week 11 of development. We also analysed the juxtaoral organ of five additional fetuses by immunohistochemistry with anti-NF-200 to verify their innervation. The results show that the juxtaoral organ may have a function in the mechanical activity of the region.

Neuroepithelial hamartoma of the oral cavity

We report a previously undescribed gingival lesion composed of squamous epithelial islands in close association with bundles of nonmyelinated nerves. A review of the pertinent literature is presented and the histologic differential diagnosis is discussed. We suggest the term neuroepithelial hamartoma for this lesion.

Nerves and Neurotropic Carcinomas

Neurotropism by a carcinoma in the head and neck refers to invasion in, around, and through peripheral nerves. This invasion may be along planes of least resistance in the connective tissue coverings of the nerve or less frequently by endolymphatic spread. The only lymphatics associated with a nerve are those in the perineural covering and in the epineurium. Such malignant neurotropism is to be distinguished from benign epithelial inclusions simulating neural invasion.

Intraneural epithelial islands associated with a periapical cyst

Epithelial islands associated with nerve bundles have been reported in the mandible and maxilla. An example of such intraneural rests is reported in association with a radicular cyst. The differential diagnosis of intraneural epithelial islands must include benign odontogenic rests, remnants of nasopalatine duct in the anterior maxilla, the organ of Chievitz, and neural invasion by a carcinoma.

A microscopic focus of traumatic neuroma with intralesional glandular structures: an incidental finding

A 50-year-old man received radiation therapy and chemotherapy for squamous cell carcinoma of the right floor of the mouth. Histologic examinations of surgical materials revealed the presence of benign ductal epithelial structures containing mucinous material within a small traumatic neuroma of the mandibular alveolar mucosa. Presumably, the residual salivary ducts of the sublingual glands may become incorporated during the development of a traumatic neuroma secondary to the destruction of tissue. Our search of the literature has failed to reveal a similar recorded occurrence.

Intraneural and perineural epithelial structures

The fact that numerous embryologic epithelial remnants are a normal occurrence in the oral region is well known. That some of these epithelial remnants occur within peripheral nerves is less well known. This study presents examples of intraneural epithelial rests from 3 different anatomic sites: the soft tissues of the jaws (a juxtaoral organ of Chievitz), the posterior maxilla (an ondotogenic rest), and the anterior maxilla (a nasopalatine duct remnant). The purpose of this paper is to draw the attention of surgical pathologists to this phenomenon in the head and neck in order to avoid extensive unnecessary surgery.