Clear Cell Squamous Cell Carcinoma of the Tongue Exhibits Characteristics as an Undifferentiated Squamous Cell Carcinoma

Microscopic findings in oral squamous cell carcinoma with cystic spaces and clear cells mimicking mucoepidermoid carcinoma: A detailed case report

A 62-year-old male was referred for management of oral squamous cell carcinoma (OSCC), previously diagnosed in another service. The patient complained of persistent oral discomfort for 10 months, reported being a social drinker, and denied smoking. Intraoral examination revealed a vegetating, hardened lesion, measuring 3.0 cm, in transition between the retromolar trigone, soft palate, and buccal mucosa. Microscopic examination of the incisional biopsy performed previously revealed malignant epithelial cells proliferate and invade the surrounding stroma as islands and cords of epithelial cells, with the presence of cystic spaces and clear cells, resembling mucoepidermoid carcinoma (MEC). The histological findings led to a diagnosis of MEC or OSCC. Based on the correlation between the morphological, immunohistochemical, and histochemical findings, the diagnosis of OSCC with cystic spaces and clear cells was supported. The patient was referred for further therapeutic intervention. Recognizing the histological variants of OSCC is important, due to the similarity with other neoplasms.

Prognostic implications across histological subtypes of head and neck squamous cell carcinoma: An update

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is one of the most common malignancies worldwide, arising from the mucosal epithelium of the oral cavity, oropharynx, hypopharynx, nasopharynx, larynx, and sinuses. In addition to the conventional morphologic pattern characterized by the degree of cellular atypia and squamous differentiation, HNSCC is classified into eight histopathologic subtypes: basaloid, spindle cell, adenosquamous, cuniculatum, verrucous, lymphoepithelial, papillary, and acantholytic.

METHODS

This review provides a comprehensive review of the literature on the prognostic implications of the histological subtypes of HNSCC.

RESULTS

Although there is extensive literature on HNSCC, few studies specifically focus on the treatment and prognosis of its histopathologic subtypes. Among these subtypes, verrucous squamous cell carcinoma and carcinoma cuniculatum generally have a favorable prognosis, while others, such as basaloid and spindle cell squamous cell carcinoma, tend to follow a more aggressive clinical course.

CONCLUSION

In this review, we delve into the histopathological subtypes of HNSCC and explore their clinicopathological, molecular, and prognostic findings. Further molecular investigations aimed at identifying targeted therapies for these subtypes are necessary. Moreover, it is crucial to recognize the emerging histopathological variants documented in the literature, considering the ongoing limitations in prognostic assessment.

Chlorogenic acid exhibits antitumor effect in patient-derived xenograft models and hydrogel-embedded tissue culture drug susceptibility test of tongue cancer

Chlorogenic acid (CGA) is one of the effective components of Chinese medicine plant such as honeysuckle and Eucommia ulmoides. CGA can inhibits various cancer types, but its effectivity against tongue cancer remains unknown. In the present study, we utilized patient-derived xenograft (PDX) models in conjunction with hydrogel-embedded drug sensitivity tests (HDST) to demonstrate the inhibitory effects of CGA on tongue cancer tissues in both in vivo and ex vivo experimental paradigms. Immunohistochemical (IHC) analysis and TUNEL staining revealed that CGA downregulated the expression of CD31 and Ki-67, while concurrently promoting apoptosis. Furthermore, the involvement of the EGFR-AKT-MMP9 signaling cascade in the tumor-suppressive effects of CGA was confirmed using network pharmacology analysis and immunofluorescent validation techniques. Overall, our findings indicate that CGA robustly inhibits tongue cancer in cellular and organismal models. The EGFR-AKT-MMP9 axis plays a highly significant role in mediating this bioactivity, thereby positioning CGA as a promising candidate for further investigation in oncology. The multifaceted therapeutic potential of CGA, as evidenced by its ability to disrupt angiogenesis, suppress cell proliferation, and induce apoptosis, underscores its value as a novel therapeutic agent for the treatment of tongue cancer.

Decoding the Rarity: A Unique Case of Clear-Cell Variant of Oral Squamous Cell Carcinoma

The clear-cell variant of oral squamous cell carcinoma is an extremely rare histological variant and an incompletely understood entity. Clear cell appearance in squamous cell carcinoma may be attributed to hydropic degeneration of neoplastic cells. We report a case of a 32-year-old male patient who presented with an ulceroproliferative growth in the left maxillary posterior region on the hard palate and gingiva, obliterating the buccal vestibule. Histopathologic examination revealed thick anastomosing strands of round to ovoid neoplastic cells with predominantly clear cytoplasm and marked cellular and nuclear pleomorphism infiltrating into the fibro-cellular connective tissue stroma. Special staining and immunohistochemistry (IHC) were performed to rule out the differentials of clear-cell variants of different sites such as salivary gland, odontogenic origin, and metastatic tumors. The clear cells were negative for periodic acid Schiff (PAS) and mucicarmine. The malignant clear cells showed positive reactions with IHC markers pan-cytokeratin and P63 and yielded negative results for S100 and CD10, confirming the diagnosis as a clear-cell variant of oral squamous cell carcinoma. We emphasize the importance of prompt and comprehensive diagnostic work-up to identify this rare, aggressive, and possibly fatal neoplasm.

Clear cell oral squamous cell carcinoma as a diagnostic conundrum: report of 2 rare cases

The occurrence of clear cell histologic sub-type of oral squamous cell carcinoma in the oral cavity is a distinct and exceedingly rare entity exhibiting aggressive behavior. To date, only 10 cases have been published in the literature. We describe 2 extremely rare cases, both presenting with swelling and ulcerated nodule-like proliferative growth in the mandible. Microscopically, sheets and lobules of neoplastic squamous epithelial cells showing clear cell differentiation were appreciated in both patients. Periodic acid-Schiff and mucicarmine revealed negative staining. Immunohistochemical (IHC) analysis for antibody for renal cell tumor marker CD 10 was immune-negative. The malignant clear cells in both cases showed intense positive reactions with IHC markers pan-cytokeratin and epithelial membrane antigen, confirming the diagnosis as a clear cell variant of oral squamous cell carcinoma (CCOSCC). The first patient was unwilling for treatment and eventually died within 2 months of the diagnosis. In the second patient, right hemi-mandibulectomy with level 1A and 1B lymph nodes was performed. Adjuvant chemotherapy with low-dose methotrexate was initiated. Follow-up after 2 months of surgery was uneventful. Current rare reports emphasize the significance of prompt and extensive diagnostic work-up of clear cell neoplasms, as the CCOSCC may be fatal.

The IL-1β-p65 axis stimulates quiescent odontogenic epithelial cell rests via TGF-β signalling to promote cell proliferation of the lining epithelia in radicular cysts: A laboratory investigation

AIM

Cyst formation of the jaws is frequently accompanied by the proliferation of odontogenic epithelial cells located in the periodontal ligament (PDL), which consists of heterozygous cells and includes the most fibroblasts. The lining epithelium of radicular cyst, an odontogenic cyst of inflammatory origin, is derived from the proliferation of the remnants of the Hertwig epithelial root sheath (odontogenic epithelial cell rests of Malassez; ERMs) in the PDL. ERMs are maintained at a lower proliferative state under physiological conditions, but the regulatory mechanisms underlying the inflammation-dependent enhanced-proliferative capabilities of ERMs are not fully understood. The aim of this study was to evaluate the effects of cytokine pathway association between TGF-β signalling and IL-1β signalling on the regulation of odontogenic epithelial cell proliferation using radicular cyst pathological specimens and odontogenic epithelial cell lines.

METHODOLOGY

Immunofluorescence analyses were performed to clarify the expression levels of Smad2/3 and Ki-67 in ERMs of 8-week-old mouse molar specimens. In radicular cyst (n = 52) and dentigerous cysts (n = 6) specimens from human patients, the expression of p65 (a main subunit of NF-κB), Smad2/3 and Ki-67 were investigated using immunohistochemical analyses. Odontogenic epithelial cells and PDL fibroblastic cells were co-cultured with or without an inhibitor or siRNAs. Odontogenic epithelial cells were cultured with or without TGF-β1 and IL-1β. The proliferative capabilities and Smad2 phosphorylation levels of odontogenic epithelial cells were examined.

RESULTS

Immunohistochemically, Smad2/3-positivity was increased, and p65-positivity and Ki-67-positivity were decreased both in ERMs and in the epithelial cells in dentigerous cysts, a non-inflammatory developmental cyst. In contrast, p65-positive cells, along with the expression of Ki-67, were increased and Smad2/3-positive cells were decreased in the lining epithelia of radicular cysts. Co-culture experiments with odontogenic epithelial cells and PDL fibroblastic cells revealed that PDL cells-derived TGF-β1/2 and their downstream signalling suppressed odontogenic epithelial cell proliferation. Moreover, TGF-β1 stimulation induced Smad2 phosphorylation and suppressed odontogenic epithelial cell proliferation, while IL-1β stimulation reversed these phenotypes through p65 transactivation.

CONCLUSIONS

These results suggest that IL-1β-p65 signalling promotes odontogenic epithelial cell proliferation through suppressing TGF-β-Smad2 signalling, which would be involved in the pathogenesis of radicular cysts.

Wnt/β-catenin-C-kit axis may play a role in adenoid cystic carcinoma prognostication

Adenoid cystic carcinoma (ACC) is one of the most common malignant salivary gland tumors. ACC is composed of myoepithelial and epithelial neoplastic cells which grow slowly and have a tendency for neural invasion. The long term prognosis is still relatively poor. Although several gene abnormalities, such as fusions involving MYB or MYBL1 oncogenes and the transcription factor gene NFIB, and overexpression of KIT have been reported in ACC, their precise functions in the pathogenesis of ACC remain unclear. We recently demonstrated that the elevated expression of Semaphorin 3A (SEMA3A), specifically expressed in myoepithelial neoplastic cells, might function as a novel oncogene-related molecule to enhance cell proliferation through activated AKT signaling in 9/10 (90%) ACC cases. In the current study, the patient with ACC whose tumor was negative for SEMA3A in the previous study, revisited our hospital with late metastasis of ACC to the cervical lymph node eight years after surgical resection of the primary tumor. We characterized this recurrent ACC, and compared it with the primary ACC using immunohistochemical methods. In the recurrent ACC, the duct lining epithelial cells, not myoepithelial neoplastic cells, showed an elevated Ki-67 index and increased cell membrane expression of C-kit, along with the expression of phosphorylated ERK. Late metastasis ACC specimens were not positive for β-catenin and lymphocyte enhancer binding factor 1 (LEF1), which were detected in the nuclei of perineural infiltrating cells in primary ACC cells. In addition, experiments with the GSK-3 inhibitor revealed that β-catenin pathway suppressed not only KIT expression but also proliferation of ACC cells. Moreover, stem cell factor (SCF; also known as KIT ligand, KITL) induced ERK activation in ACC cells. These results suggest that inactivation of Wnt/β-catenin signaling may promote C-kit-ERK signaling and cell proliferation of in metastatic ACC.

Clear Cell Squamous Cell Carcinoma of the Maxillary Gingiva Associated with PIK3CA and HRAS Mutations: Report of a Case and Literature Review

BACKGROUND

Squamous cell carcinoma (SCC) is the most common oral malignancy, and somatic mutations in some driver genes have been implicated in SCC development. Clear cell SCC (CCSCC) is a rare histological variant of SCC, and various clear cell neoplasms must be considered in the differential diagnosis of CCSCC in the oral cavity. Based on a limited number of CCSCC cases reported in the oral cavity, CCSCC is considered an aggressive variant of SCC with a poor prognosis; however, its genetic characteristics remain unknown.

METHODS

A maxillary gingival tumor in an 89-year-old female was described and investigated using immunohistochemical staining, special staining, fluorescence in situ hybridization, and next-generation sequencing (NGS) with a custom panel of driver genes, including those associated with SCC and clear cell neoplasm development.

RESULTS

Histopathological examination revealed a proliferation of atypical epithelial cells with abundant clear cytoplasm and enlarged and centrally placed round nuclei. The tumor was exophytic with deep, penetrating proliferation. The atypical clear cells were continuous with the conventional SCC cells. Immunohistochemical analysis showed that the clear cells were positive for CK AE1/AE3 and CK5/6 and nuclear-positive for p63. In contrast, the clear cells were negative for αSMA, S100, HMB45, Melan-A, CD10, and p16. p53 immunoreactivity exhibited a wild-type expression pattern. Additionally, the clear cells were positive for periodic acid-Schiff (PAS) and negative for diastase-PAS, mucicarmine, and Alcian blue. Based on these results, the diagnosis of CCSCC was confirmed. Molecular analysis of the clear cells identified PIK3CA p.E542K (c.1624G>A) and HRAS p.G12A (c.35 G>C) somatic mutations classified as oncogenic. No pathogenic variants were identified in TP53, EWSR1, AKT1, PTEN, BRAF, KRAS, NRAS, RASA1, or MAML2.

CONCLUSIONS

We report a case of CCSCC of the oral cavity with PIK3CA and HRAS mutations. The identification of PIK3CA and/or HRAS mutations is rare in SCC; however, both mutations are important potential targets for antitumor therapy. A detailed analysis of gene mutations in CCSCC may lead to a better understanding of its biological behavior and an improved prognosis, as well as a differential diagnosis from other clear cell neoplasms.

Arl4c is involved in tooth germ development through osteoblastic/ameloblastic differentiation

Murine tooth germ development proceeds in continuous sequential steps with reciprocal interactions between the odontogenic epithelium and the adjacent mesenchyme, and several growth factor signaling pathways and their activation are required for tooth germ development. The expression of ADP-ribosylation factor (Arf)-like 4c (Arl4c) has been shown to induce cell proliferation, and is thereby involved in epithelial morphogenesis and tumorigenesis. In contrast, the other functions of Arl4c (in addition to cellular growth) are largely unknown. Although we recently demonstrated the involvement of the upregulated expression of Arl4c in the proliferation of ameloblastomas, which have the same origin as odontogenic epithelium, its effect on tooth germ development remains unclear. In the present study, single-cell RNA sequencing (scRNA-seq) analysis revealed that the expression of Arl4c, among 17 members of the Arf-family, was specifically detected in odontogenic epithelial cells, such as those of the stratum intermedium, stellate reticulum and outer enamel epithelium, of postnatal day 1 (P1) mouse molars. scRNA-seq analysis also demonstrated the higher expression of Arl4c in non-ameloblast and inner enamel epithelium, which include immature cells, of P7 mouse incisors. In the mouse tooth germ rudiment culture, treatment with SecinH3 (an inhibitor of the ARNO/Arf6 pathway) reduced the size, width and cusp height of the tooth germ and the thickness of the eosinophilic layer, which would involve the synthesis of dentin and enamel matrix organization. In addition, loss-of-function experiments using siRNAs and shRNA revealed that the expression of Arl4c was involved in cell proliferation and osteoblastic cytodifferentiation in odontogenic epithelial cells. Finally, RNA-seq analysis with a gene set enrichment analysis (GSEA) and Gene Ontology (GO) analysis showed that osteoblastic differentiation-related gene sets and/or GO terms were downregulated in shArl4c-expressing odontogenic epithelial cells. These results suggest that the Arl4c-ARNO/Arf6 pathway axis contributes to tooth germ development through osteoblastic/ameloblastic differentiation.

The Semaphorin 3A-AKT axis-mediated cell proliferation in salivary gland morphogenesis and adenoid cystic carcinoma pathogenesis

We recently demonstrated that Semaphorin 3 A (Sema3A), the expression of which is negatively regulated by Wnt/β-catenin signaling, promotes odontogenic epithelial cell proliferation, suggesting the involvement of Sema3A in tooth germ development. Salivary glands have a similar developmental process to tooth germ development, in which reciprocal interactions between the oral epithelium and adjacent mesenchyme proceeds via stimulation with several growth factors; however, the role of Sema3A in the development of salivary glands is unknown. There may thus be a common mechanism between epithelial morphogenesis and pathogenesis; however, the role of Sema3A in salivary gland tumors is also unclear. The current study investigated the involvement of Sema3A in submandibular gland (SMG) development and its expression in adenoid cystic carcinoma (ACC) specimens. Quantitative RT-PCR and immunohistochemical analyses revealed that Sema3A was expressed both in epithelium and in mesenchyme in the initial developmental stages of SMG and their expressions were decreased during the developmental processes. Loss-of-function experiments using an inhibitor revealed that Sema3A was required for AKT activation-mediated cellular growth and formation of cleft and bud in SMG rudiment culture. In addition, Wnt/β-catenin signaling decreased the Sema3A expression in the rudiment culture. ACC arising from salivary glands frequently exhibits malignant potential. Immunohistochemical analyses of tissue specimens obtained from 10 ACC patients showed that Sema3A was hardly observed in non-tumor regions but was strongly expressed in tumor lesions, especially in myoepithelial neoplastic cells, at high frequencies where phosphorylated AKT expression was frequently detected. These results suggest that the Sema3A-AKT axis promotes cell growth, thereby contributing to morphogenesis and pathogenesis, at least in ACC, of salivary glands.