Oral carcinoma cuniculatum, an unacquainted variant of oral squamous cell carcinoma: A systematic review

Gingival Carcinoma Cuniculatum: A Case Series of Seven Cases with Emphasis on Immunohistochemical and Histochemical Features

Oral carcinoma cuniculatum (CC) is a rare distinct variant of oral squamous cell carcinoma (OSCC) displaying unique clinical and histopathological features. CC is a locally aggressive malignancy with lower metastatic potential and has a tendency to invade the underlying bone yielding nonspecific clinical presentation resembling fungal/bacterial infections or osteomyelitis. Seven rare cases of gingival CC are reported with special emphasis on immunohistochemistry and special stains. Clinical and demographic profile were analysed and all cases were subjected to Ki-67 and p53 immunostaining and Ayoub-Shklar histochemical staining. For comparison, age and gender matched seven cases of conventional OSCC with bony involvement were recruited. IBM SPSS statistics software version 26 (IBM Analytics, Armonk, New York, U.S.) was used to analyse the data. All cases of CC lacked p53 expression in contrast to OSCC and demonstrated intermediate to high proliferation index in stroma also. The keratin staining and cytokeratin profile in OSCC and CC were also found to be statistically different. CC is a rare well differentiated variant of OSCC with different pathways involved in the pathogenesis. Local aggressive and invasive nature could be the result of unique interaction between epithelium and stromal elements. Oral health care provider must be familiar with this uncommon variant of OSCC.

Management and treatment of four cases of oral carcinoma cuniculatum

Objectives

Oral carcinoma cuniculatum (OCC) is a rare variant of squamous cell carcinoma (SCC). It has similar clinicopathological characteristics to SCC and verrucous carcinoma (VC). We present a case series of OCC and analyse its unique features, diagnosis, and management. Patients and.

Methods

We retrospectively reviewed the medical records of oral cancer patients treated by Oral and Maxillofacial Surgery department from 2009 to 2020 with OCC biopsy findings. The clinicopathological characteristics and management of the OCC cases were analysed.

Results

Four patients were identified with histologic findings of OCC, including three on the alveolar ridge mucosa and one on the tongue. Imaging revealed that two of the lesions located in the maxilla had osseous lysis. All four patients were all treated with radical excision, and the histopathology showed findings of SCC cuniculatum. It was decided that no further treatment was necessary. None of the patients has experienced recurrence during follow-up.

Conclusion

OCC is a distinct entity that is more locally aggressive than VC but is associated with good prognosis. Radical surgical removal is considered appropriate for OCC. Emphasis should be given on an early diagnosis, as it remains challenging.

"Salivary LINC00657 and miRNA-106a as diagnostic biomarkers for oral squamous cell carcinoma, an observational diagnostic study"

BACKGROUND

Early detection and diagnosis of malignant tumors is critical for improving the survival rate and treatment outcomes of oral cancer. Thus, the current prospective investigation was designed to verify the role, sensitivity, and specificity of salivary LINC00657 and miRNA-106a as diagnostic markers in oral squamous cell carcinoma patients as compared to oral lichen planus (as an example of oral potentially malignant disorders) and normal individuals, and to show LINC00657 relation to miR-106a.

METHODS

A total of 36 participants were included, subdivided into 3 groups: Group I: 12 patients diagnosed with oral squamous cell carcinoma (OSCC). Group II: 12 patients diagnosed with oral lichen planus (OLP). Group III: 12 systemically free individuals with no oral mucosal lesions. Unstimulated salivary samples were collected from all participants to evaluate level of LINC00657 and miR-106a in different groups using quantitative real-time PCR.

RESULTS

OSCC showed the highest LINC00657 and lowest miR-106a fold change among included groups. Receiver Operating Characteristic (ROC) curve analysis of the two biomarkers for detecting OSCC revealed that LINC00657 had higher diagnostic accuracy (DA) (83.3%) compared to miR-106a (80.4%). As for detecting OLP, ROC analysis showed that miR-106a had higher (DA) (61%) compared to LINC00657 (52.5%). To discriminate OSCC from OLP, the diagnostic accuracy of both markers is the same (75%). Moreover, differentiating OSCC grades II and III, ROC analysis showed that miR-106a had lower (DA) (60%) compared to LINC00657 (DA) (83.3%).

CONCLUSIONS

Salivary LINC00657 and miR-106a could be promising diagnostic markers for oral squamous cell carcinoma. Salivary LINC00657 may differentiate oral squamous cell carcinoma from oral potentially malignant disorders with considerable diagnostic accuracy. Moreover, low levels of salivary miR-106a could have the potential to indicate malignancy.

TRIAL REGISTRATION

The study was retrospectively registered on clinicaltrial.gov with NCT05821179 (first trial registration in 26/3/2023), date of registration: 19/4/2023.

Oral carcinoma cuniculatum, a rare variant of squamous cell carcinoma

INTRODUCTION

Carcinoma cuniculatum (CC) is a rare variant of squamous cell carcinoma (SCC). Lack of awareness of this tumor and its difficult diagnosis delay management and complicate treatment. The aim of this study is to describe the clinical and histological features, predisposing factors, treatment and survival rate of oral carcinoma cuniculatum.

MATERIAL & METHOD

All patients with histologically confirmed CC of the oral cavity treated between January 2013 and August 2022 in a specialized center were retrospectively included. Patients were identified using the database ADICAP ("Association pour le Développement de l'Informatique en Cytologie et Anatomie Pathologique"). Once identified, the charts were reviewed.

RESULTS

Ten patients were included. CC lesions were mainly located in the mandibular or maxillary gingiva, while the 2 remaining lesions were located in the mobile tongue. The tumor showed local aggressiveness: mandibular or maxillary osteolysis was systematically found for gingival CC, while tongue lesions were classified cT3. Fifteen biopsies were performed in these 10 patients, histological diagnosis is difficult on a limited tissue sample. All patients underwent curative management with oncological excision surgery combined with neck lymph node dissection, and adjuvant radiotherapy (except one patient).

DISCUSSION

The main problem is the difficulty of diagnosis when biopsies are performed, which leads to a significant delay in diagnosis compared with SCC. In the event of clinico-histological discordance after biopsy, CC should be considered.

Carcinoma Cuniculatum of the Maxilla Arising From Oroantral Fistula: A Report of an Extremely Rare Case

Carcinoma cuniculatum (CC) is extremely rare in the maxilla. Here, we report a case of CC arising from an oroantral fistula (OAF). The patient was a 70-year-old Japanese man who was followed up for a non-closing OAF. Although there were no findings based on an intraoral examination, follow-up contrast-enhanced computed tomography and magnetic resonance imaging showed a 22-mm mass in the maxilla close to the OAF. Histologically, cystic and endophytic papillary proliferation of squamous epithelium with abundant keratinization mimicking rabbit burrows occupied the alveolar bone. This tumor was directly connected to the atypical proliferation of the covering epithelium of the OAF. The tumor cells showed mild cytological atypia and a few mitoses. Finally, the patient was diagnosed with CC arising from an OAF. CC is often misdiagnosed; nonetheless, the unique endophytic, branching, and tunnel-like structure is a hallmark of this tumor. We present the first well-documented case of CC arising from an OAF, discuss its diagnostic features, and highlight its differences from other common benign and malignant pathological entities.

Epidemiology and incidence of oral squamous cell carcinoma in the Iraqi population over 5 years (2014-2018)

Background

Oral squamous cell carcinoma is one of the most common and life-threatening neoplasms worldwide, and is responsible for approximately 90% of all oral malignancies.

Aim

This study was aimed at providing updated information on oral squamous cell carcinoma in all Iraqi governorates for the 5-year period from 2014 to 2018, including the annual incidence and demographic variables.

Materials and Methods

The total number of oral squamous cell carcinoma cases in Iraq, along with associated demographic information (age, sex, and site), for the 5-year period from 2014 to 2018 was obtained. The statistical analysis consisted of descriptive analysis, including frequency, percentage, and mean ± standard deviation. A χ ² test was performed to compare frequencies between male and female patients, among age groups, and among different OSCC sites. The χ ² test was also used to assess the association of each OSCC site with age and sex. The significance threshold was set at p < 0.05, and the confidence interval was set at 95%. The incidence rate of oral squamous cell carcinoma for each year was calculated by dividing the number of OSCC cases per year by the population of Iraq, then multiplying the result by 100,000.

Results

A total of 722 cases were recorded. Statistically, oral squamous cell carcinoma was found to be more prevalent in males and individuals over 40 years of age. The tongue was the most common site of occurrence. Lip squamous cell carcinoma cases were high in males. The incidence rate of oral squamous cell carcinoma was estimated to be 0.4 per 100,000 people.

Conclusion

Males and older people are at relatively higher risk of developing oral cancer. The tongue is the most affected site, but any site in the oral cavity may be involved. Further exploration of the causes of oral malignancy in Iraq is necessary to improve prevention strategies.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Tumours of the Oral Cavity and Mobile Tongue

The fifth chapter of the upcoming fifth edition of the 2022 World Health Organization Classification of Tumours of the Head and Neck titled Tumours of the oral cavity and mobile tongue, has had some modifications from the 2017 fourth edition. A new section "Non-neoplastic Lesions", introduces two new entries: necrotizing sialometaplasia and melanoacanthoma. The combined Oral potentially malignant disorders and Oral epithelial dysplasia section in the 2015 WHO has now been separated and submucous fibrosis and HPV-associated dysplasia are also discussed in separate sections. Carcinoma cuniculatum and verrucous carcinoma are described in dedicated sections, reflecting that the oral cavity is the most common location in the head and neck for both these entities which have distinct clinical and histologic features from conventional squamous cell carcinoma. This review summarizes the changes in Chapter 5 with special reference to new additions, deletions, and sections that reflect current clinical, histological, and molecular advances.

Cuneiform (cuniculatum) variant of oral squamous cell carcinoma revisited: Presentation of two cases and literature review of a rare entity

BACKGROUND

Oral carcinoma cuniculatum (OCC) is a rare, locally aggressive tumor, which tends to invade underlying bone. We present two cases of OCC, one demonstrating invasion of the mandible and the other limited to the tongue.

METHODS

An 87-year-old male presented with a right-sided buccogingival lesion. Biopsy results led to a diagnosis of verrucous hyperplasia, which was later revised to OCC. Additionally, a 94-year-old female presented with a left lateral tongue lesion. A biopsy showed in-situ and invasive keratinizing squamous cell carcinoma that was later defined as a soft tissue OCC.

RESULTS

Following surgical resection, the diagnosis of OCC was established in both patients. We provide a comprehensive literature review of OCC in the context of both case presentations.

CONCLUSIONS

OCC is a rare entity, which has a tendency to be misdiagnosed. We emphasize the importance of recognizing the common features of OCC in order to aid in accurate diagnosis.

Oral carcinoma cuniculatum: an unacquainted entity with diagnostic challenges-a case report

BACKGROUND

Oral carcinoma cuniculatum (OCC) is an unacquainted well-differentiated subtype of oral squamous cell carcinoma, which displays unique clinic-pathological features. Up to date, OCC remains rare with about 75 reported cases, and is frequently missed or even misdiagnosed.

CASE PRESENTATION

The aim of the present work was: to report a case of OCC in mandibular gingiva and to highlight its main clinic-pathological diagnostic features: with an exophytic cobble-stone surface and a characteristic endophytic burrowing architecture, as well as to differentiate between it and other closely similar lesions including verrucous carcinoma, papillary squamous cell carcinoma, and well-differentiated conventional oral squamous cell carcinoma.

CONCLUSIONS

An accurate diagnosis of OCC entails awareness of the clinicians and pathologists about its entity, proper knowledge of the diagnostic clinical and histopathological evidence, and the ability to differentiate it from closely similar lesions.

Carcinoma Cuniculatum of the Oral Cavity: A Series of 6 Cases and Review of Literature

Carcinoma cuniculatum (CC) is a rare variant of squamous cell carcinoma (SCC) that is characterized by minimal cytologic atypia and a unique deeply infiltrative growth pattern resembling rabbit burrows (cuniculi). With less than 75 cases reported in the head and neck, the clinical and pathologic spectrum of this entity remains poorly understood. A retrospective review of the clinical and pathologic features of archival cases of oral CC was performed. A total of six cases of oral CC were identified. Age ranged from 25-77 years; the male-to-female ratio was 5:1. All patients had a long-standing history of tobacco and betel-quid consumption. The tumors were distributed in the gingivobuccal sulcus (n = 2), the tongue (n = 2), buccal mucosa (n = 1), and the palate (n = 1). Histology in all cases typically revealed a tumor composed of well-differentiated squamous epithelium, devoid of atypia, lining deeply infiltrative, large-sized, branching, keratin-filled cavities, resembling rabbit-burrows. Dense lymphocytic infiltrates and discharging micro-abscesses were regular features. Underlying bone invasion and lymph node metastasis were observed in 1 patient. One patient with a tongue tumor developed locoregional recurrence at 10 months while none developed distant metastasis. Oral CC is a rare and under-recognized variant of SCC with locally aggressive behavior. Lack of familiarity with this variant exacerbated by the absence of cytologic anaplasia makes CC susceptible to multiple negative biopsies and erroneous diagnoses. Awareness of this clinicopathologic entity is essential to allow its accurate diagnosis and optimal management.

Carcinoma Cuniculatum of Mandible Masquerading as Odontogenic Keratocyst: Challenges in the Histopathological Diagnosis

Carcinoma cuniculatum is a locally aggressive, low-grade variant of squamous cell carcinoma. Though primarily a tumour of the skin, it has also been found to be arising from various mucosal surfaces including oral mucosa. When it occurs in the mandible it starts as a mucosal lesion which progressively invades the jaw and destroys the underlying bone, often presenting as a cystic lesion. With only around 30 cases reported in the mandible, this entity remains an elusive one for the pathologist and all except a few cases reported so far, had been misdiagnosed initially. The delay in the diagnosis is a major concern as it results in further progression of the disease with extensive involvement of bone and associated soft tissue structures. The aim of this article is to discuss the histopathological challenges faced in arriving at the diagnosis of a case of carcinoma cuniculatum involving the mandible. Owing to its overlapping clinico-pathological characteristics with odontogenic keratocyst the lesion has been misdiagnosed initially resulting in inadequate management, leading to multiple recurrences and unexpected complications. As a few cases like the present one had been erroneously diagnosed as odontogenic keratocyst previously, it becomes important to identify the varied clinical presentation and unique histopathological characteristic of carcinoma cuniculatum of mandible to help us in recognizing this often-missed entity at an earlier stage, so that it can be managed effectively.

Cystic Squamous Cell Carcinomas of the Jaws: Twelve Cases Highlighting Histopathological Pitfalls

Cystic squamous cell carcinomas (SCCs) of the jaws, including carcinoma cuniculatum, are rare, slow growing, and relentlessly invasive. The aim of this article is to present 12 cases, 4 of which were designated as carcinoma cuniculatum on the basis of deeply endophytic, anastomosing channels of cystic stratified squamous epithelium and keratin microabscesses. The other 8 were also cystic, but more heterogeneous morphologically and were diagnosed as well differentiated SCCs. Six patients were female, 6 were male (mean age = 74.0 years, range = 50-94 years). Six tumors affected the mandible, 6 the maxillary alveolus with or without extension into the hard palate. All patients underwent primary resection with neck dissection and were staged as T4a N0 M0. In 4 patients, diagnosis was delayed as a result of superficial biopsies and/or confusing histopathology. Cystic SCCs of the jaws can be difficult to diagnose and clinicoradiological correlation is essential. Long-term follow-up is mandatory.

METTL3 Facilitates Oral Squamous Cell Carcinoma Tumorigenesis by Enhancing c-Myc Stability via YTHDF1-Mediated m6A Modification

N⁶-Methyladenosine (m⁶A) is the most common internal modification of eukaryotic messenger RNA (mRNA) that occurred on the N⁶ nitrogen of adenosine. However, the roles of m⁶A in oral squamous cell carcinoma (OSCC) are still elusive. Here, we investigate the function and mechanism of methyltransferase-like 3 (METTL3) in OSCC tumorigenesis. Clinically, METTL3 was significantly upregulated in tissue samples and correlated with the poor prognosis of OSCC patients. Functionally, loss and gain studies illustrated that METTL3 promoted the proliferation, invasion, and migration of OSCC cells in vitro, and METTL3 knockdown inhibited tumor growth in vivo. Mechanistically, methylated RNA immunoprecipitation sequencing (MeRIP-seq) illustrated that METTL3 targeted the 3′ UTR (near to stop codon) of the c-Myc transcript to install the m⁶A modification, thereby enhancing its stability. Furthermore, results revealed that YTH N⁶-methyladenosine RNA binding protein 1 (YTH domain family, member 1 [YTHDF1]) mediated the m⁶A-increased stability of c-Myc mRNA catalyzed by METTL3. In conclusion, our findings herein identify that METTL3 accelerates the c-Myc stability via YTHDF1-mediated m⁶A modification, thereby giving rise to OSCC tumorigenesis.