Ultrastructure of oral squamous-cell carcinoma

Usefulness of Five-Parameter System Reconfirmed for Cytopathology of Oral Squamous Cell Carcinoma regardless of Differentiation Degree

BACKGROUND

We previously introduced the Five-Parameter System (FPS), which exclusively evaluates keratinized cellular findings, for use in cytology examinations of oral well-differentiated squamous cell carcinoma (SCC) and carcinoma in situ (CIS) specimens, as they occasionally lack nuclear atypia and can be challenging for categorization by The Bethesda System (TBS). This study was conducted to determine whether FPS parameters are detectable even in oral SCC/CIS specimens with apparent nuclear atypia.

SUMMARY

Oral cytology specimens were obtained together with biopsy tissue samples. They were obtained from 59 malignant (HSIL and SCC) and 29 not-definitely malignant (NILM to ASC-H) specimens diagnosed using TBS. Following re-confirmation of the original TBS categorization, the specimens were re-evaluated using FPS. One or more of the FPS parameters were noted in 69 of 70 malignant specimens examined, of which 11 had been diagnosed by TBS as not-definitely malignant. The remaining one malignant specimen was diagnosed as SCC with only TBS. FPS parameters #1 (concentric arrangement), #2 (large cell number), #3 (bizarre-shaped cells), #4 (keratoglobules), and #5 (uneven filamentous cytoplasm) were observed only in malignant cases, while none were revealed in not-definitely malignant specimens. Finally, TBS supplemented with FPS achieved sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of 100%.

KEY MESSAGES

FPS parameters are included in most examinations of oral cytology specimens. Thus, FPS is highly recommended for use in cytology examinations of oral SCC regardless of differentiation degree to confirm judgment based on TBS, a mandatory standard, as well as to cover its limitation of mainly evaluating nuclear atypia. FPS is considered to be an important diagnostic tool for oral cytology, especially in triage cases, which are challenging for TBS. Cytopathology should not be limited to only nuclear findings but be based on whole-cell morphology.

Characterization of oral squamous cell carcinoma based on higher-harmonic generation microscopy

In vivo higher-harmonic generation microscopy (HGM) performed on healthy human oral mucosa not only provides images with a <500 nm lateral resolution at a 280 μm penetration depth, but also leaves no photodamages in the tissues. These advantages suggest that HGM could serve as an ideal virtual biopsy tool for in vivo, in situ, and immediate histopathological diagnosis of oral cancer. However, translation of such mechanism for clinical cancer diagnosis requires evidence based algorithm capable to differentiate cancerous tissues from normal. It is thus critical to investigate if the endogenous contrast provided by the HGM would be high enough to differentiate cancerous versus normal tissues in human oral mucosa. In this report, ex vivo HGM study was performed on the cancerous mucosa from 10 patients with oral squamous cell carcinoma. Compared with histology, HGM revealed histopathological features including the cytological abnormalities, loss of differentiation, interruption of basement membrane, and irregular epithelial stratification in all 10 specimens. In addition, distinct patterns of collagen fibers and increased distribution area of actin filaments in tumor cells were noted. These results indicate HGM holds great potential for the optical biopsy screening of oral cancer lesions.

Ultrastructural changes of the palatal mucosa following application of 4-nitroquinoline-l-oxide (4NQO) in rats subjected to major salivary gland excision

OBJECTIVE

It has been suggested that saliva exerts a protective role against the carcinogenic effect of various substances in the oral cavity. The objective of this study was to examine the ultrastructural changes of the palatal mucosa caused by the application of 4-nitroquinoline-l-oxide (4NQO) in the presence or absence of saliva.

STUDY DESIGN

Wistar-Furth rats subjected and not subjected to total bilateral excision of the major salivary glands were either painted with an aqueous solution of 4NQO or with propylene glycol only (controls). Two animals of each group were humanely killed periodically. The areas of the palatal lesions were immediately sliced and processed for TEM examination.

RESULTS

Ultrastructurally, the progressive changes to squamous cell carcinoma were observed in the animals painted with 4NQO. In the desalivated animals group, the ultrastructural alterations appeared earlier than in the group with salivary glands.

CONCLUSIONS

Saliva appeared to delay but not hinder tumor induction by 4NQO.

An immunohistochemical and ultrastructural study of syringocystadenoma papilliferum

BACKGROUND

Syringocystadenoma papilliferum is a benign hamartomatous tumour of the skin. The histogenesis of this tumour is still controversial. There have been few reports regarding immunohistochemical investigations using only a limited range of antibodies and ultrastructural studies on this rare tumour.

OBJECTIVES

To elucidate the immunohistochemical and ultrastructural properties of this tumour.

METHODS

We investigated the immunohistological patterns of 12 different anticytokeratin (CK) antibodies and several other markers in five cases of this tumour, comparing them with the patterns in adult sweat glands. One of these cases was also evaluated ultrastructurally.

RESULTS

The luminal columnar cells of the tumour were mostly positive for CK7 and more than 70% were positive for CK19. These cells showed the heterogeneous expression of CK1/5/10/14, CK14 and CK5/8. These patterns were also observed in the luminal cells in the secretory or the ductal portion of the adult sweat glands. The basal cuboidal cells of the tumour almost constantly expressed CK1/5/10/14, CK5/8, CK14 and CK7 (except for one case), similar to the patterns of basal cells in the transitional portion and myoepithelial cells in the sweat glands. However, the basal tumour cells expressed CK19 and vimentin heterogeneously, and alpha-smooth muscle actin focally (three cases). Ultrastructurally, the constituent epithelial cells were mainly divided into three types: luminal cells, basal cells and clear cells. The luminal tumour cells bore features of the secretory or ductal luminal cells of sweat glands, although they were somewhat immature in appearance. The basal tumour cells were fundamentally basaloid in nature. The clear cells were undifferentiated or primitive in appearance, suggesting stem or progenitor cell properties. Transitional forms between the clear cells and the other two cell types were also identified.

CONCLUSIONS

The tumour epithelium was composed of several cell types demonstrating various developmental stages from the primitive clear cells to the basal cells demonstrating a tendency to differentiate toward basal cells in the apocrine transitional portion or myoepithelial lineage, or luminal cells toward the ductal or secretory epithelium. These results support the classical concept that syringocystadenoma papilliferum is a hamartomatous tumour that arises from pluripotent cells.

Ultrastructural changes in malignant transformation of oral mucosa

Transmission electron microscopy (EM) has been used to identify the ultrastructural details of normal and cancerous human oral mucosa. However, inconsistent reports of structural descriptions have rendered transmission EM valueless in the diagnosis of oral squamous cell carcinoma (SCC) or as a prognostic indicator. To identify features of dysplasia for diagnostic purposes, normal mucosa, severe dysplasia, oral SCC and normal margin adjacent to oral SCC were used to compare the ultrastructural features of normal and premalignant oral mucosa and oral SCC. The preparatory stages of dehydration, embedding, cutting and positive staining for transmission EM were modified and tested to improve ultrastructural definition. Thin and discontinuous basal laminas were found in mucosa with severe dysplasia and normal margin adjacent to oral SCC. No basal lamina was identified in oral SCC. This study has shown that there are some ultrastructural changes during malignant transformation of oral mucosa. Together with other laboratory investigative techniques, transmission EM may be helpful in detecting malignant changes in oral mucosa.

Oral cancer: role of the basement membrane in invasion

Invasive growth of cancer cells is a complex process involving specific interactions between tumour cells and the orderly, integrated complexes of the extracellular matrix. Basement membranes have been proposed as one constituent of extracellular matrix which carries responsibility for regulating invasion and metastasis. Using a chemically induced rat tongue carcinoma model, it has been shown that components of the basement membrane and its overall structure are altered during tumour invasion, and methods have been developed to quantitate some of these differences. Since the basement membrane can be specifically characterized by its fibrous protein network of Type IV collagen and laminin, which is embedded in a heparan sulphate-rich proteoglycan matrix, these components have been targeted. In particular, the current paper presents results in the context of current concepts of early changes in neoplastic invasion of underlying connective tissues. In consequence, further elaboration of the underlying mechanisms of epithelial migration in oral cancer may allow an exploration of the use of alterations in expression of basement membrane components as prognostic indicators.

Ultrastructural analysis of the adjacent epithelium of oral squamous cell carcinoma

Fifteen biopsies of the immediate adjacent epithelium of oral squamous cell carcinoma were examined under light and electron microscopy. Light microscopic examination of one micron thick sections revealed that the majority of lesions (67%) had hyperplastic or mildly dysplastic epithelium while the remaining (33%) had moderate to severe dysplasia. Ultrastructural observations showed that all these lesions had subcellular alterations similar to those seen in frank malignant oral tissue, particularly in the lower half of the epithelium. Important ultrastructural changes observed included bizarre nuclei of basal and lower spinal cells, enlarged and multiple nucleoli, presence of interchromatin and perichromatin granules, loss of desmosomes and marked spongiosis as well as disturbed cellular maturation sequences in the keratinocytes evidenced by abnormal and irregular distribution of maturation markers such as keratohyalin granules and tonofilaments. The present study thus shows the value of electron microscopy in the detection of malignant changes in the adjacent epithelium of oral squamous cell carcinoma.

Ultrastructure of oral squamous cell carcinoma: a comparative analysis of different histological types

Twenty-five oral carcinomas and five normal oral epithelial specimens were studied using light and electron microscopy. All histological types (well differentiated squamous cell carcinoma, moderately differentiated squamous cell carcinoma, poorly differentiated squamous cell carcinoma, verrucous carcinoma and spindle cell carcinoma) were seen in the study sample. In addition, 1 case of carcinoma in situ was also present. The normal oral epithelium consisted of three keratinising types (gingiva) and two non-keratinising types (buccal mucosa). The ultrastructural features of oral carcinomas showed good correlation with the features seen in light microscopy. The differentiation status of the lesions showed a relationship with cell and nuclear size, tonofilament and keratin content as well as few other cellular abnormalities. It was also observed that the fine details revealed by electron microscopy were often a means of explaining the characteristic histopathological features of oral carcinoma.

Oncogenes, tumor suppressors and viruses in oral squamous carcinoma

The pathogenesis of oral squamous cell carcinoma involves recognised carcinogens in tobacco and/or alcohol but other factors, including viruses, may also have a role. This paper reviews the gene changes revealed in oral carcinoma, the evidence implicating viruses, and mechanisms whereby viruses may affect gene function.

Ultrastructural features of normal epithelium and 4-nitroquinoline 1-oxide-induced carcinomas of the rat tongue

An electron microscopical examination of normal rat lingual mucosa and 4-nitroquinoline 1-oxide (4NQO)-induced tongue carcinomas was undertaken. In normal rat tongue, the epithelium of papillae and interpapillary regions exhibited two distinct keratohyalin granule types and essentially similar ultrastructural cellular features in the different epithelial compartments. The interface between epithelium and connective tissue showed a continuous basal lamina. Compared with normal rat tongue epithelium, 4NQO-induced oral carcinomas revealed cellular and nuclear pleomorphism, atypical tonofilament aggregates, increased and swollen mitochondria, dilated intercellular spaces, local discontinuities and thickening of the basal lamina.

Viruses in the aetiology of oral carcinoma? Examination of the evidence

This paper examines the evidence for an aetiological role for viruses in the development of oral carcinoma. Several viruses have been sought in oral cancer and evidence found for some, particularly herpes simplex and human papillomavirus. However, the evidence also suggests that these viruses are ubiquitous agents and a number of criteria must be met before these potentially oncogenic agents can reliably be implicated in human carcinogenesis. In contrast, there is no evidence that viruses such as adenovirus, Epstein-Barr virus, and retroviruses play any role in oral carcinogenesis.

Viruses and chronic disorders involving the human oral mucosa

Viruses have been implicated in the etiology of several chronic disorders of the oral mucosa. Most of these associations have been with DNA viruses, particularly certain herpesviruses, which are associated, for example, with some cases of erythema multiforme and with hairy leukoplakia. Papillomaviruses are associated with various papillomatous lesions, focal epithelial hyperplasia, and possibly with some carcinomas. Viruses may possibly be associated with recurrent aphthae, Behçet's syndrome, and some dermatoses. The literature concerning these possible associations is reviewed. However, much more research needs to be done before the full story of viral associations with oral mucosal disorders can be written.

Oral cancer

In the U.S. oral cancer accounts for 2.1% of all cancers and 1% of cancer deaths. Two to three times as many males as females are affected. Blacks have more intra-oral cancer than whites, and their incidence and mortality rates have increased in recent years. The etiologic process very likely involves several factors. The major etiologic agents are tobacco (all types) and alcoholic beverages. Herpes simplex virus, human papilloma virus, and Candida have been implicated. Host factors include poor state of dentition, nutritional aberrations, cirrhosis of liver, lichen planus, and immunologic impairmant. Cellular changes include amplification of some oncogenes, alterations in antigen expression, production of gamma-glutamyl transpeptidase, and disturbance of keratin and involucrin production. Experimentally, cancer is readily produced on the hamster cheek pouch and rat oral mucosa. Unlike oral cancer in humans, most experimental lesions are exophytic, and they rarely metastasize.

Evaluation of histopathologic parameters in predicting cervical lymph node metastasis of oral and oropharyngeal carcinomas

A retrospective study of 53 patients with squamous cell carcinomas of the oral cavity and oropharynx was undertaken to evaluate histopathologic parameters in predicting cervical lymph node metastasis. Biopsy and surgical specimens were examined for degree of differentiation, pattern and depth of stromal invasion, lymphatic-vascular invasion, and lymphoplasmacytic response in relation to metastasis. The incidence of lymph node metastasis in tumors showing grade III type diffuse invasion (71.4%) and with stromal invasion of more than 8 mm in depth (83.3%) was significantly higher than that of tumors with well-demarcated boundaries (44.4% to 5.2%) and superficial invasion (35.3% to 8.3%). Lymph node metastasis also increased in the presence of lymphatic-vascular invasion by tumor cells, whereas the degree of differentiation and lymphoplasmacytic response was not related to metastasis. Thus, the pattern and the depth of stromal invasion and the presence of lymphatic-vascular invasion were important indicators in prediction of cervical lymph node metastasis. Prophylactic neck dissection is advocated when grade III type diffuse invasion, invasion exceeding 8 mm in depth, or grade II type invasion accompanied by a 4 mm to 8 mm depth of invasion is observed in a biopsy specimen.

Herpes simplex virus type 1 proteins in human oral squamous cell carcinoma

Although considerable evidence has accumulated linking herpes simplex virus (HSV) to carcinoma of the uterine cervix, only fragmentary evidence exists linking HSV to oral cancer. The purpose of this study was to search for HSV type 1 (HSV-1) proteins in tissue sections of 132 oral squamous cell carcinomas and 56 age- and site-matched controls. All tissues were incubated in rabbit anti-HSV-1 serum with the use of a modified direct immunoperoxidase technique. More than 42% of the cancers, but none of the controls, reacted positively. Thirteen selected oral carcinomas that exhibited positive polyclonal staining were incubated with the use of a peroxidase-antiperoxidase technique with a mouse monoclonal antibody raised against the 89 kilodalton HSV-1 envelope protein. None of these tissues exhibited a positive reaction. Similarly, no unequivocal ultrastructural viral particles were found in 11 oral carcinomas that stained positively with the polyclonal antibodies. These results are interpreted to indicate partial expression of a noninfectious viral genome. The presence of this genome in a high proportion of lesions in this study lends strong statistical support to the oncogenic relationship between HSV-1 and oral squamous cell carcinoma.

Ultrastructure of oral leukoplakia and lichen planus. I. Basal region and inflammatory cells

Nine cases of homogenous leukoplakia and 21 cases of lichen planus (11 reticular and 10 erosive) were studied under the electron microscope. The changes found in leukoplakia were limited to occasional breaks in the basal lamina and modest changes in the cytoplasm of the basal cells. The basal lamina in lichen planus was found to exhibit 3 distinctly different pictures reflecting the clinical types of lichen planus. The structural abnormalities in the basal cells increased with increasing severity of the lesions. The inflammatory infiltrate in lichen planus was found to contain mainly small-to-medium-sized lymphocytes but plasma-cells with widely dilated rough endoplasmic reticulum containing a granular substance were frequently seen. Similar changes are seen in other disorders and, therefore, specific diagnostic criteria cannot be established on the basis of the present material.

Microfilaments in human cementoblasts and periodontal fibroblasts

An electron microscopic survey was carried out on the human periodontal ligament (PDL), including a part of the gingival connective tissue attached to extracted tooth roots (11 functioning premolars and 6 nonfunctioning third molars) in order to examine the characteristics of microfilaments (6 nm) in cementoblasts and PDL fibroblasts. Microfilaments which were grouped in bundles with semiperiodic dense nodes or in meshworks just beneath the cell membrane were seen predominantly in the cells characterized by their ultrastructurally immature appearance. These microfilaments were more commonly observed in third molar PDL than in premolar PDL and, in general, more conspicuous in cementoblasts than in fibroblasts. The significance of microfilaments in human PDL is discussed, particularly in relation to cell differentiation and morphogenesis.

Histodifferentiation and ultrastructure of oral squamous cell carcinoma in HMT rats

Seven oral squamous cell carcinomas developed in HMT rats were studied with light and electron microscopy. Two carcinomas in extra-oral sites were also described. Histodifferentiation of oral squamous cell carcinomas ranged from well-differentiated to poorly-differentiated, comparable to that of the same disease in humans. Ultrastructural features characteristic of human oral carcinomas were observed in the HMT rat carcinomas.

Canalicular adenoma of the buccal mucosa. An ultrastructural and histochemical study

A canalicular adenoma that occurred in the minor salivary glands of the buccal mucosa in a 62-year-old black man was examined by electron microscopy and histochemistry. The ulcerated bowl-shaped tumor consisted mostly of ductlike tubules of columnar and cuboidal epithelial tumor cells which resembled intercalated duct cells ultrastructurally. Tumor cells resembling myoepithelial cells were not associated with these tubules. Less frequently, there were narrow tubules and cords adjacent to the capsule. Occasional cells in these cords contained variable amounts of microfilaments, often associated with focal densities, and thus resembled myoepithelial cells in varying stages of differentiation. Other noteworthy ultrastructural findings in this neoplasm included marked replication of the basal lamina of capillaries and the presence of a single, luminally oriented cilium in a tumor cell lining a tubule.

An ultrastructural study of epidermolytic leukoplakia

A leukoplakic lesion of the lip showing the histologic features of epidermolytic hyperkeratosis above solar elastosis was investigated by electron microscopy. The ultrastructural alterations observed in the upper epidermal layers corresponded in the main with those of epidermolytic hyperkeratosis in other skin diseases. The keratinocytes showed irregularly formed tonofilaments, a marked intracellular edema, and premature cornification. In addition, there were discrete subcellular signs of premalignancy in the cells of the basal and suprabasal layers. These alterations suggest that the epidermolytic leukoplakia represents a rare histopathologic variant of actinic cheilitis.

Ultrastructural changes of epithelium-connective tissue junction in experimental lingual tumors

In this study, plaque-like lesions, epithelial hyperplasias, and papillary invasive carcinomas were produced in the tongues of hamsters by the application of DMBA combined with trauma for 16 weeks. The junction between the neoplastic epithelial cells and the connective tissue was studied ultrastructurally. In plaque-like lesions, the basal lamina was partially decreased in both thickness and density or partially discontinuous. In epithelial hyperplasias, cytoplasmic projections were observed in the portion of the basal cell near the intercellular space, and the basal lamina was absent around these cytoplasmic projections. In papillary invasive carcinomas, however, numerous cytoplasmic projections extended from various portions of the basal surface of the basal cells into the underlying connective tissue. The basal lamina was also absent around these projections. In epithelial hyperplasias and papillary invasive carcinomas, some of the cytoplasmic projections appeared almost empty, some contained a small number of tonofilaments and ribosomes, and others were filled with a large number of ribosomes but did not contain the tonofilaments. The collagen fibrils were markedly reduced in number in the area around cytoplasmic projections. The cytoplasm of some fibroblasts in that area contained many intracellular collagen fibrils.

Morphologic changes in rat parotid following isoproterenol administration and fractionated x-irradiation

The effects of fractionated X-irradiation following isoproterenol (IPN) administration on rat parotid gland were studied 4, 8, and 12 weeks post-irradiation. Degenerative and necrotic changes of the acinar cells were observed at all three time intervals as a result of the radiation. These changes were more obvious 4 and 8 weeks post-irradiation and isoproterenol administration. The necrotic acinar cells were replaced by fibrous connective tissue, especially conspicuous at 12 weeks. Reparative changes were observed along with the degenerative and regressive phenomena of the gland. Enlarged acinar cells and nuclei were observed as early as 4 weeks post-irradiation. This change was focally distributed at the 4-week interval but more widespread 8 and 12 weeks post-irradiation. Mitochondrial hyperplasia with alteration of mitochondrial cristae was observed 12 weeks post-irradiation. Proliferation of cells of ductal origin and nodular proliferation of ducts were observed 12 weeks after isoproterenol administration plus X-irradiation. These proliferative phenomena may represent an early stage of tumor formation resulting from the combined effect of isoproterenol and X-irradiation on rat parotid gland.

Oral cancer and herpes simplex virus--a review

Numerous studies have suggested that patients with oral cancer have an increased immune response to herpes simplex virus. However, the number of cases has always been small, and essential controls have not always been included. Laboratory experiments have shown that herpes simplex virus can be carcinogenic or cocarcinogenic under certain circumstances and so must be considered as a possible etiologic agent in oral cancer. This article reviews past research and suggests priorities for future investigations.

Ultrastructural alterations in experimental lingual leukoplakia and carcinoma

Epidermoid carcinomas, preceded by dysplastic leukoplakic lesions, were produced on the right lateral borders of the tongues of Syrian hamsters by the application, three times per week, of DMBA in acetone after the area had been scratched with a root canal broach. Animals were killed at 12 to 13 weeks and 15 to 16 weeks. Electron microscopic studies of both the dysplastic leukoplakic lesions and the well-differentiated epidermoid carcinomas revealed clumping of tonofilaments and widening of intercellular spaces, in addition to the cellular pleomorphism, altered nuclear-cytoplasmic ratio, and prominent nucleoli observed with the light microscope. In the carcinomas, there were variations in the morphology of mitochondria, with tubular forms in evidence. The basal lamina in the carcinomas was discontinuous. Pseudopodia arising from basal cells were seen in areas of basal lamina discontinuity.

Demonstration of actin in oral epithelial cells

Two human sera with antibodies against smooth muscle were used to investigate the distribution of actin in moving oral epithelial cells by immunocytochemical methods. Epithelial outgrowths from explants of rat and human oral mucosa showed a constant positive staining in the peripheral parts of the marginal cells but not in the more central parts of the epithelial sheet. This is in agreement with theories of the importance of the marginal cells in the migratory behavior of the epithelial outgrowth. Subcultured epithelial cells from the human explants showed positive staining of fine fibers in the cytoplasm. During healing of experimental oral wounds from humans and monkeys actin fibers could be demonstrated in only one of 18 cases in the epithelial cells adjacent to the wound, though positive staining of various cells was seen in the underlying tissue. This is in contrast to the evidence presented in previous studies of cells taking part in the re-epithelialization process.