Alterations in Stromal Reaction During Tumor Progression in Oral Mucosa

Tumor Microenvironment in Oral Squamous Cell Carcinoma: Special Stains and Scanning Electron Microscopic Study

Background

Effect of the oral cancerous epithelial cells on the extracellular matrix (ECM) and vice versa is also responsible for the growth and progression of cancer. The effect of inflammation on the stroma and its association with progression has also been stated in literature.

Materials and Methods

The control group consisted of 10 patients with apparently normal mucosa with no history of habits, the study group consisted of 30 patients with oral squamous cell carcinoma (OSCC) confirmed by examination and incisional biopsy. H and E staining, Masson's Trichrome Staining, and Verhoeff's Van Gieson staining were used to study the inflammation, collagen fibers, and elastic fiber, respectively. A few selected specimens were studied under the scanning electron microscope. The grade of inflammation was statistically correlated with collagen and elastic fibers.

Observation

Grade of inflammation was closely associated with lymphadenopathy and the density of collagenous and elastic components of the ECM. The scanning electron microscopic evaluation of elastic fibers revealed irregular fragmented elastic fibers.

Conclusion

The stroma is the key to complete removal and treatment of OSCC; however, more studies are needed to define the role of each component, therefore improving the prognosis of a patient.

An Immunohistochemical and Polarizing Microscopic Study of the Tumor Microenvironment in Varying Grades of Oral Squamous Cell Carcinoma

BACKGROUND

Invasion of epithelial cells into the connective tissue brings about massive morphological and architectural changes in the underlying stroma. Myofibroblasts reorganize the stroma to facilitate the movement of tumor cells leading to metastasis. The aim of this study was to determine the number and pattern of distribution of myofibroblasts and the qualitative and quantitative change that they cause in the collagen present in the stroma in various grades of oral squamous cell carcinoma (OSCC).

METHODS

The study was divided into two groups with group I (test group, 65 cases) consisting of 29 cases of well-differentiated squamous cell carcinoma, 25 moderately differentiated SCC, and 11 poorly differentiated SCC, and group II (control group) consisting of 11 cases of normal mucosa. Sections from each sample were stained with anti-α-smooth muscle actin (α-SMA) antibodies, hematoxylin and eosin, and Picrosirius red. Several additional sections from each grade of OSCC were stained with Masson's trichrome to observe the changes in collagen. For the statistical analysis, Fisher's exact test, Tukey's post hoc honest significant difference test, ANOVA, and the chi-square test were used, and p < .05 was considered statistically significant.

RESULTS

As the tumor stage progressed, an increase in the intensity α-SMA expression was seen, and the network pattern dominated in more dedifferentiated carcinomas. The collagen fibers became thin, loosely packed, and haphazardly aligned with progressing cancer. Additionally, the mean area fraction decreased, and the fibers attained a greenish yellow hue and a weak birefringence when observed using polarizing light microscopy.

CONCLUSIONS

Myofibroblasts bring about numerous changes in collagen. As cancer progresses, there isincrease in pathological collagen,which enhances the movement of cells within the stroma.

Histochemical analysis of collagen reorganization at the invasive front of oral squamous cell carcinoma tumors

AIM

The aim of the present study was to: (a) analyze the nature of collagen with respect to cohesive and discohesive invasive tumor front (ITF) of oral squamous cell carcinoma (OSCC); (b) analyze the clinicopathological correlation with the nature of collagen at the ITF of OSCC; and (c) correlate the nature of collagen with Broder's and Bryne's histological grading system of OSCC.

METHODS

Tissue sections of 29 OSCC with ITF were stained with hematoxylin-eosin and picrosirius red staining for evaluation under a polarized microscope.

RESULTS

Tumors with a cohesive front had a thick collagen fiber, are predominantly organized, red-yellow in color, well packed, and show strong birefringence (P<.005). A gradual change in the nature of the collagen fiber was observed in the discohesive tumor front, where the collagen fibers were thin, disorganized, yellow-orange to green-yellow in color, loosely packed, and with weak birefringence (P<.005).

CONCLUSION

A cohesive tumor front with organized collagen fibers prevents tumor invasion and metastasis. As it is inhibits an increase in tumor size, it is associated with the initial stage of tumor (I & II), whereas in a discohesive tumor front, the fibers might enhance the movement of tumor cells, resulting in invasion and metastasis.

Expression of immunoregulatory molecules PD-L1 and PD-1 in oral cancer and precancerous lesions: A cohort study of Japanese patients

OBJECTIVE

An association of the programmed cell death-1 (PD-1) and its ligand PD-L1 with various types of malignant tumors has been established. This study aimed to investigate the role of the PD-L1/PD-1 pathway in oral squamous cell carcinoma (OSCC) and oral epithelial precursor lesions (OEPL).

MATERIALS AND METHODS

We examined 106 OSCC and 79 OEPL specimens for PD-L1 and PD-1 expression by immunohistochemistry. The results were compared with clinicopathological features of OSCC patients.

RESULTS

In OSCC and OEPL specimens, PD-L1 expression was detected predominantly in epithelial or carcinoma cells, whereas PD-1 expression was found mainly in infiltrating or stromal lymphocytes. Seventy-two OSCC (67.9%) and 21 OEPL (26.6%) specimens were positive for PD-L1, and 73 OSCC (68.9%) and 23 OEPL (29.2%) specimens were positive for PD-1. PD-L1 and PD-1 expression levels were significantly different between OEPL and OSCC specimens (P < 0.001). There were significant positive correlations between PD-L1 and PD-1 expression in OEPL and OSCC specimens (P < 0.001). PD-L1 and PD-1 immunoreactivity was significantly associated with tumor size (P < 0.05). PD-L1 and PD-1 immunoreactivity in cases with advanced TNM staging was significantly higher than that in low staging cases (P < 0.01). There were significant correlations between PD-L1 and PD-1 expression in OSCC specimens and pathological variables such as stromal lymphocytic reaction (P < 0.05) and invasion depth (P < 0.01).

CONCLUSION

PD-L1 and PD-1 immunohistochemical status may be related to carcinogenesis, tumor progression, and prognosis in oral epithelial lesions. Agents targeting PD-1 and PD-L1 might be useful for OSCC treatment.