Basaloid squamous cell carcinoma: a 31-year retrospective study and analysis of 214 cases reported in the literature

Basaloid Squamous Cell Carcinoma, an Aggressive and Rare Cancer of the Oral Cavity: Can We Prevent It at the Primary Care Setting?

Oral cavity cancer represents about 2%-3% of all cancers worldwide, with more than 355,000 new cases per year, one-third of which are reported in developed countries. Oral cancer is also known to be extremely aggressive when detected late, thus presenting one of the lowest cancer survival rates. It is estimated that as much as 90% of oral cancers are attributable to tobacco and/or alcohol consumption and that high-risk human papillomaviruses (HPV) infections pose an independently increased risk for their development. Therefore, it can be a preventable disease when associated with changes in lifestyle and possible modifiable risk factors, combined with early and preventive intervention. Basaloid squamous cell carcinoma (BSCC) constitutes an aggressive and rare form of oral cancer, being one of the rarest and most aggressive variants of squamous cell carcinoma (SCC, the most common), and usually presents as a high-grade disease with a poor prognosis. It is typically associated with heavy smoking and alcohol abuse, occurring most commonly in older men. Here, we report a clinical case of a 60-year-old man with excessive consumption of both tobacco and alcohol, poor oral hygiene, and partial edentulousness who came to our primary health department with complaints of odynophagia twice in a four-year time-lapse. The first time, two whitish ulcerated lesions on the left tonsil were detected and biopsied but revealed a negative histological result. After four years, he came again to our primary health care department with similar complaints of odynophagia and also sore throat with radiation to the right ear, accompanied by globus sensation and anorexia. No suspicious lesions were detected, except a globally hyperemic oropharynx. Considering the history of abusive consumption, no improvement with symptomatic treatment, and persistent clinical signs, an extended diagnostic approach was carried out. After four months, a pharyngeal mass measuring 53 mm was detected on pharyngeal-neck computed tomography (CT), and the diagnosis of a BSCC located in the right tonsillar pillar and base of the tongue was finally determined. Unlike other cancers that have been detected earlier through screening programs, oral cancer is often detected at an advanced stage, compromising survival and quality of life. The opportunity to intervene early and preventively in consumption habits, promote healthy lifestyles, and try to prevent disease is unique at the primary care level. Moreover, opportunistic screening through a thorough examination of the oral cavity is extremely important for timely diagnosis and treatment.

[Clinicopathological study in 28 cases of oral basaloid squamous cell carcinomas]

OBJECTIVE

To investigate the clinicopathologic features and prognostic factors in oral basaloid squamous cell carcinoma.

METHODS

Retrospective analysis of oral basaloid squamous cell carcinomas patients who underwent tumor resection during the period from January 2002 to December 2020 in the authors' hospital, especially the clinicopathologic characteristics of 28 cases with confirmed diagnosis and follow-up data. Immunohistochemistry was performed to define the helpful markers for differentiation diagnosis. The factors influencing the prognosis were evaluated based on Kaplan-Meier method.

RESULTS

The tongue and mouth floor (11 cases, 39.3%) were the most frequently involved sites, followed by gingiva (6 cases, 21.4%), buccal (5 cases, 17.9%), palate (4 cases, 14.3%), and oropharynx (2 cases, 7.1%). The majority of basaloid squamous cell carcinomas were in advanced stage, with 12 cases in stage Ⅱ and 16 cases in stages Ⅲ-Ⅳ. Twelve of 28 patients were identified to have cervical lymph node metastasis, which was confirmed by histopathological examination. The incidence rate of lymph node metastasis was 42.9% (12/28). Nine tumors recurred, with one metastasized to the lung. At the meantime, the 28 conventional squamous cell carcinomas were matched with the same stage, among which 13 cases were identified with cervical lymph node metastasis. The incidence rate of lymph node metastasis was 46.4% (13/28). Five cases recurred, with two cases that metastasized to the lung and one to the brain. The 5-year overall survival rates of the basaloid squamous cell carcinoma and conventional squamous cell carcinoma patients were 54.6% and 53.8%, respectively. Histopathologically, basaloid cells consisted of tumor islands without evident keratinization but frequently with comedo-like necrosis within the tumor islands. CK5/6 and P63 exhibited strongly positive in all the 28 cases, whereas neuroendocrine markers, CgA and Syn, were negative. Eight cases positively expressed P16; one case showed focal SOX10 positive but CK7 negative.

CONCLUSION

The majority of oral basaloid squamous cell carcinomas present in advanced stage with a high tendency to lymph node metastasis, but the overall survival rates are not significantly different from conventional squamous cell carcinomas matched with the same stage. The human papilloma virus (HPV), as HPV-positivity rate is high, correlates to good prognosis. In addition, CK7 & SOX10 immunohistochemistry could contribute to differential diagnosis for basaloid squamous cell carcinoma with solid adenoid cystic carcinoma.

Constitutive Hedgehog/GLI2 signaling drives extracutaneous basaloid squamous cell carcinoma development and bone remodeling

Uncontrolled activation of the Hedgehog (Hh) signaling pathway, operating through GLI transcription factors, plays a central role in the pathogenesis of cutaneous basal cell carcinoma and contributes to the development of several malignancies arising in extracutaneous sites. We now report that K5-tTA;tetO-Gli2 bitransgenic mice develop distinctive epithelial tumors within their jaws. These tumors consist of large masses of highly proliferative, monomorphous, basaloid cells with scattered foci of keratinization and central necrosis, mimicking human basaloid squamous cell carcinoma (BSCC), an aggressive upper aerodigestive tract tumor. Like human BSCC, these tumors express epidermal basal keratins, and differentiation-specific keratins within squamous foci. Mouse BSCCs express high levels of Gli2 and Hh target genes, including Gli1 and Ptch1, which we show are also upregulated in a subset of human BSCCs. Mouse BSCCs appear to arise from distinct epithelial sites, including the gingival junctional epithelium and epithelial rests of Malassez, a proposed stem cell compartment. Although Gli2 transgene expression is restricted to epithelial cells, we also detect striking alterations in bone adjacent to BSCCs, with activated osteoblasts, osteoclasts, and osteal macrophages, indicative of active bone remodeling. Gli2 transgene inactivation resulted in rapid BSCC regression and reversal of the bone remodeling phenotype. This first-reported mouse model of BSCC supports the concept that uncontrolled Hh signaling plays a central role in the pathogenesis of a subset of human BSCCs, points to Hh/GLI2 signaling as a potential therapeutic target, and provides a powerful new tool for probing the mechanistic underpinnings of tumor-associated bone remodeling.

[Modern perspectives of oral squamous cell carcinoma]

The article is devoted to the modern perspectives of the etiology, pathogenesis, diagnosis and prognostic factors in theoral squamous cell carcinoma. In the new edition of the WHO Classification of Head and Neck Tumors of 2017, the concept of potentially malignant diseases is introduced, which include erythroplakia, leukoplakia, oral submucous fibrosis, dyskeratosiscongenita, smokeless tobacco keratosis, palatallesions associated with reverse smoking, chronic candidiasis, lichen planus, discoid lupus erythematosus, syphilitic glossitis and actinic keratosis (liponly). A binary system for assessing oral epithelial dysplasia assessing is proposed. In Chapter 5, a separation of squamous cell carcinoma with a positive and negative reaction to human papillomavirus (HPV) is performed. It has been shown that patients with HPV positive squamous cell carcinoma have a better prognosis of the disease, which confirms the clinical distinction between oropharyngeal tumors and oral mucosa.