Hamster tongue carcinogenesis II. Quantitative morphologic aspects of preneoplastic epithelium

Analysis of images for detection of oral epithelial dysplasia: A review

This paper provides a review of various image analysis approaches that have been previously used for recognition of dysplasia in images of the epithelium of the oral cavity. This domain has become especially admissible with the uncovering of the importance of image analysis which can probably be an aid to subjective diagnosis by histopathologists. Oral malignancy is a rampant form of cancer found among people of the Indian subcontinent due to various deleterious habits like consumption of tobacco, areca nut, betel leaf etc. Oral Submucous Fibrosis, a precancer, whose pathological category falls between normal epithelium and epithelial dysplasia, is caused because of these habits and can ultimately lead to oral cancer. Hence early detection of this condition is necessary. Image analysis methods for this purpose have an enormous potential which can also reduce the heavy workload of pathologists and to refine the criterion of interpretation. This paper starts with a critique of statistics of oral carcinoma in India and distribution of cancer in intra-oral sites and moves on to its causes and diagnostic approaches including causative agents, problems in curative approach and importance of image analysis in cancer detection. The various image analysis methods to appraise the cytological and architectural changes accompanied by Oral Epithelial Dysplasia in the images of the oral epithelial region have been described in relation to 2005 WHO Classification System and it was found that in future, analysis of images based on the mentioned methods has the potential in better interpretation and diagnosis of oral carcinoma.

Histomorphometric study to compare histological changes between oral squamous cell carcinoma and apparently normal adjacent oral mucosa

Despite the advances in surgery, radiotherapy and chemotherapy the annual death for oral squamous cell carcinoma (OSCC) is rising rapidly. The carcinoma has propensity to develop in a field of cancerization. Clinically may it be apparently normal mucosa (ANM) adjacent to squamous cell carcinoma which harbours certain discrete molecular alteration which ultimately reflects in cellular morphology. Hence the aim of the study is to assess histomorphometric changes in ANM adjacent to OSCC. A prospective study was done on 30 each of histologically diagnosed cases OSCC, ANM at least 1 cm away from OSCC, and normal oral mucosa (NOM). Cellular and nuclear morphometric measurements were assessed on hematoxylin and eosin sections using image analysis software. Statistical analysis was done using analysis of variance test and Tukey's post hoc test. The present study showed significant changes in cellular and nuclear area in superficial and invasive island of OSCC compared to ANM. The basal cells of ANM showed significant decrease in cellular and nuclear areas and nuclear cytoplasmic ratio when compared to NOM. Histomorphometry definitely can differentiate OSCC form ANM and NOM. The basal cells of ANM showed significant alterations in cellular area, nuclear area and nuclear cytoplasmic area when compared to NOM suggesting change in the field and have high risk of malignant transformation. These parameters can be used as indicator of field cancerization.

Morphometry of the basal cell layer of oral leukoplakia and oral squamous cell carcinoma using computer-aided image analysis

Objectives:

To study and compare the changes in nuclear and cellular size, shape and nuclear–cytoplasmic ratio of the cells in the basal layer of oral leukoplakia and well-differentiated oral squamous cell carcinoma (SCC) with normal buccal mucosa, using computer-aided image analysis in tissue sections.

Study design:

This was a retrospective study conducted on tissue sections on a total number of 70 cases to determine the various morphometric parameters. The data collected in this study were analyzed statistically by computing descriptive statistics, viz., percentage, mean, standard deviation, standard error of mean, 95% confidence interval for mean. The difference in the control and study groups for various diagnostic variables was compared by means of analysis of variance (ANOVA), Student’s t-test for independent samples, wherever applicable. Mann–Whitney U-test and Kruskal–Wallis test were used where the data were found to be asymmetrical and the standard deviations were also different. The results were considered statistically significant whenever P ≤ 0.05.

Results:

Our results were significant for the morphometric parameter, size. The values of nuclear perimeter and area, cellular perimeter and area increased gradually from the normal buccal mucosa to leukoplakia, reaching the highest value in SCC. There was statistically significant difference in the nuclear and cellular areas to differentiate between leukoplakia and squamous cell carcinoma. Two variables which were used to study the shape, “form perimeter (PE)” and “contour index (CI)”, showed significant difference between normal buccal mucosa and leukoplakia and between normal buccal mucosa and SCC. The morphometric parameter, nuclear–cytoplasmic ratio, in our results showed an increase in leukoplakia and SCC compared to normal buccal mucosa, but the difference was not significant between leukoplakia and SCC.

Conclusion:

The morphometric parameter, size, was useful to differentiate between normal, potentially malignant leukoplakia and SCC.

Morphometric computer-assisted image analysis of oral epithelial cells in normal epithelium and leukoplakia

BACKGROUND

There are very few studies documenting morphometric parameters of normal oral mucosa and leukoplakia. The present study was undertaken to establish the morphometric parameters of the parabasal and spinous cells of normal oral epithelium. Analysis of changes occurring in these cells in leukoplakia was also done.

METHODS

This study was conducted on tissue sections of clinically normal oral mucosa and leukoplakia. Morphometric analysis was done for parabasal and spinous cells. Statistical analysis was done using one way ANOVA and Mann-Whitney test.

RESULTS

Morphometric parameters were greater in the spinous cells than in parabasal cells in normal oral mucosa. Leukoplakia showed greater cellular and nuclear parameters than normal mucosa.

CONCLUSION

Normal oral epithelium showed site-wise difference in cell and nuclear measurements. Nuclear parameters showed a statistically significant change than cellular parameters in dysplasia. These changes were expressed in the earliest stage of transformation to dysplasia.

Preliminary assessment of the epithelial nuclear-cytoplasmic ratio and nuclear volume density in human palatal lesions

We have analysed both the nuclear-cytoplasmic (N/C) ratio and nuclear volume densities (VVN) in defined strata from human hard palate lesions with and without malignant potential to determine the prognostic reliability and/or validity of this parameter. Measurements of cellular and nuclear areas of basal and spinous cells from normal (N) and pathological palatal epithelium were made on histological sections using an image analyser. The lesions comprised fibrous hyperplasia (FH), traumatic inflammation (INF), benign hyperkeratosis (HK), squamous cell papilloma (PP), dysplastic epithelium adjacent to invasive carcinoma (CE) and islands of invasive squamous cell carcinoma (CI). In basal cells, no significant differences were detected in comparisons of N/C and VVN between all pathological groups and the N control group. The mean value for CE was lower than that obtained for N. In spinous cells, the only statistically significant comparison was between IF and FH for both N/C and VVN. Both parameters were lower in CE than in N. Of all groups analysed except CI, the CE group is the only one likely to possess an increased malignant potential. The N/C ratio therefore seems to be of no value as a predictor of malignancy in palatal epithelial lesions.

Histoquantitative study of inflamed tongue mucosa

A quantitative, semiautomatic analysis of histologic features of the specific inflammatory changes occurring on the dorsum of human tongue was made for 37 tongues. Well-documented histologic differences between clinically normal appearing tongue (control), atrophic, geographic and fissured tongue were shown quantitatively. The epithelium of atrophic tongue was thinner compared to the controls. Reduction of the thickness was due to the shortened or totally missing rete pegs. Epithelium of geographic and fissured tongue showed irregular rete pegs. In fissured tongue heavy inflammation seemed to shorten the rete pegs. In atrophic tongue the connective tissue was thicker compared to the controls. This could be due to mild, chronic inflammation causing loose connective tissue described in atrophic tongue. Muscle cells of geographic tongue appeared to be as in the controls, whereas in atrophic and fissured tongue the uppermost muscle cells were small and separated compared to the controls.

Quantification of oral epithelial hyperplasia in rats after topical application of the carcinogen 4-nitroquinoline 1-oxide

Hyperplasia of the palatal epithelium was quantified in two groups of rats exposed thrice weekly to the carcinogen 4NQO for 2 weeks and 2 months, respectively. The lengths and areas of the epithelial layers were measured with a computerized line-following device. In the group treated for 2 weeks the maximum area of the nuclear layer was nearly three times and the maximum length of the epithelial/connective tissue interface almost twice the normal at the end of the carcinogen application period. The maximum area of the cornified layer was three times and the maximum lengths of the epithelial surface and the keratin/nuclear layer interface almost one and a half times the normal 1 week after painting with 4NQO. Thereafter the lengths and areas decreased gradually in both experimental groups. The area of the cornified layer and the length of the epithelial/connective tissue interface in the group treated for 2 months were significantly larger than those in animals treated for 2 weeks. These variables may be two of several indicators of prognostic significance in the assessment of dose-related premalignant epithelial hyperplasia.

Epithelial dysplasia produced by carcinogen pretreatment and subsequent wounding

Golden hamsters in which the tongues were pretreated with DMBA for 4 weeks, subsequently excised, and either received no treatment or received additional postexcisional applications of acetone or DMBA for 9 to 13 days exhibited histologic evidence of epithelial dysplasia; these dysplastic lesions stained positive for papillomavirus genus-specific antigens. Conversely, animals in which the tongues received the same pretreatment yet had no excision failed to show any dysplastic changes, even though the tongues received additional applications of DMBA. Furthermore, papillomavirus genus-specific antigens were not demonstrable. The animals in which the tongues received no pretreatment with DMBA for 4 weeks followed by excisional wounding showed normal healing, even though the tongues were post-treated with DMBA. Papillomavirus genus-specific antigens could not be demonstrated in this last group.

Morphometric analysis of suprabasal cells in oral white lesions

Surgical specimens from the cheek mucosa of 73 patients with white lesions were studied to determine various morphometric parameters that would help differentiate between the various types of oral mucosal white lesions that carry a risk of malignant change. Four cell types were represented: traumatic keratosis, leucoplakia, candidal leucoplakia and lichen planus, in addition to a control group of normal mucosa. The shape and size of the epithelial cells in two cell compartments, parabasal and spinous, were investigated by an interactive image analysis system (IBAS-1). The results showed an increase in the cell size in the parabasal cell compartment of all the white lesions compared with the normal mucosa. In the spinous cell compartment there was an increase in the cell size in lichen planus and traumatic keratosis; leucoplakia and candidal leucoplakia showed a slight decrease in cell size compared with the normal mucosa. Attempts to discriminate between the four groups of white lesions showed that these parameters can provide a high level of separation between lichen planus and the three other groups, but not between leucoplakia, candidal leucoplakia, and traumatic keratosis.

Histomorphometric analysis of epithelial changes in chemically induced oral mucosal carcinogenesis in rats

Quantitative analysis of rat palatal mucosa after the carcinogen 4- nitroquinoline-1-oxide had been applied to the epithelium for varying periods of time showed that there was a significant increase in epithelial thickness, due largely to an increase in thickness of the basal compartment. This alteration was measurable before epithelial dysplasia could be recognised.

Morphometric analysis of basal cell layer in oral premalignant white lesions and squamous cell carcinoma

The size and shape of the cells in the basal cell layer of the oral epithelium in 100 specimens from oral mucosa were studied by using an interactive image analysis system (IBAS-1). Four groups of white lesions (traumatic keratosis, lichen planus, leucoplakia, and a "risk group") in addition to two control groups (normal mucosa and squamous cell carcinoma) were studied retrospectively. The results showed a progressive increase in the dimensions (area, perimeter, and maximum diameter) of the nuclei from normal mucosa through traumatic keratosis, lichen planus, leucoplakia and the "risk group" to carcinoma, with considerable differences. The nucleus in squamous cell carcinoma was twice as large as in normal mucosa. A substantial increase in the dimensions of both the cell and the nucleus was found in the "risk group." The nucleo:cytoplasmic ratio, contrary to what might have been anticipated in risk lesions, did not show considerable differences between the diagnostic groups. Furthermore, it was slightly decreased in the risk group compared with the normal mucosa. The shape factors (form PE and contour index) seemed to be less helpful in the identification of the "risk group." The size of the basal cell and its nucleus can be of diagnostic value for lesions with a high risk of malignant transformation.

Effect of excisional wounding on DMBA-induced hamster tongue carcinogenesis

The purpose of this study was to investigate histologically the effect of wounding on the hamster tongue after pretreatment with DMBA. The animals in which the tips of the tongues were pretreated with DMBA for 8 weeks, subsequently excised, and had no treatment or received applications of acetone, showed epithelial dysplasias. The animals which had the same pretreatment, excision, and received additional post-excision applications of DMBA for 9-13 days, developed squamous cell carcinomas. However, the animals which were pretreated with DMBA for 8 weeks but had no excision, did not show any pathologic changes, even though they received additional applications of DMBA for 9-13 days. The animals which received no pretreatment with DMBA for 8 weeks but had an excision, showed normal wound healing, even though they had a post-treatment with DMBA for 9-13 days. The results of the present study indicated that excisional wounding acted as a promotional stimulus in inducing the appearance of epithelial dysplasias or carcinomas of tongues initiated with the carcinogen DMBA.

Hamster tongue carcinogenesis. I. Characteristics of the experimental model

Thrice weekly applications of DMBA to hamster ventral lingual mucosa, preceded by scratching with a barbed broach, led to tumor development in over 75% of the animals by 28 weeks. Macroscopic ulceration did not appear to be a necessary precursor of epithelial malignancy in this model. Tumors were preceded by a phase resembling human leukoplakia. In addition to developing tumors in the treated area, 60% of the hamsters developed tumors in the floor of the mouth or the area of mucosa on either side of the median lingual frenum.