Conspicuous and frank dilated vascular spaces: A marker of malignant transformation in oral submucous fibrosis

Abstract

Histo-morphological alterations observed at mucosal surgical margins can be envisaged as potential markers of malignant transformation. In this paper, we have presented a very striking observation at the mucosal surgical margins of oral squamous cell carcinoma arising in the background of oral submucous fibrosis (OSCC-OSMF). Out of 38 cases of OSCC-OSMF, 22 (57.89%) showed conspicuous large dilated vascular spaces lined by endothelial cells in the background of dense fibrosis. These large dilated areas were engorged with red blood cells and were located at the juxta-epithelial and submucosal regions. Since surgical margin tissues are biologically close to malignant transformation, we proposed this unique feature as a potential predictive marker for oral submucous fibrosis that will aid in the early detection of OSCC. Future cohort studies are warranted to prove the authenticity of the present observations.

Highlights

• •Surgical margin tissues are biologically close to events related to malignant transformation.
• •Surgical margin tissues of OSCC-OSMF were histologically evaluated.
• •Significant number of cases (57.89%) showed conspicuous and frank dilated vascular spaces.
• •Presence of such vascular spaces can be envisaged as potential marker of malignant transformation.

1. Introduction

Histological assessment of surgical margins is a routine event in day-to-day surgical oncology practice. By virtue of close proximity to cancerous tissue, surgical mucosal margins are regarded as morphologically and biologically close to carcinogenesis and malignant transformation. Hence, any molecular, histological or clinical alterations seen at the mucosal margins can be envisaged as potential predictive biomarkers of malignant transformation.¹

Due to the rise in betel quid chewing habit, the incidence of oral submucous fibrosis (OSMF) is increasing every year and so is increasing the incidence of oral squamous cell carcinoma in the background of OSMF (OSCC-OSMF).² Hence, it becomes important to target this group of OSCC to identify the marker for early detection of malignant transformation in OSMF patients.³ Unfortunately, due to the atrophic nature of the epithelium, grading of epithelial dysplasia is not possible in OSMF tissues and hence, they cannot be envisaged and tested further as a marker of malignant transformation.¹ However, in our pathology practice, we observed a very remarkable and conspicuous feature in the connective tissue (stromal) component of the surgical margins in OSCC-OSMF patients, that otherwise is not present routinely in OSMF tissues.

2. Observations and discussion

From the archives, we analyzed mucosal surgical margins of a total of 96 OSCC cases. Total 38 (39.5%) cases were designated as OSCC-OSMF with the presence of typical histopathological features of OSMF at the surgical margins such as atrophic epithelium, flattening of rete ridges and dense collagen bundles in the connective tissue stroma. Out of 38 cases, 22 (57.89%) showed conspicuous large dilated vascular spaces lined by endothelial cells. In all the cases, these large dilated spaces were engorged with red blood cells and were located at the juxta-epithelial and submucosal regions (Fig. 1). Apart from the regular small compressed capillaries, total 7.31 ​± ​4.88 such large vascular spaces were seen per high power field. Intriguingly, the dilated and engorged vascular spaces were seen in the background of fibrous stroma suggesting histological evidence of OSMF (Fig. 1C and D). One case showed an extremely high number of such vascular spaces which gave a false impression of capillary hemangioma (Fig. 1B and D). The majority of the cases were reported as well-differentiated OSCC (n ​= ​11) followed by moderately differentiated (10) OSCC. A poor grade of tumor differentiation was reported in one case. However, no significant histomorphological variations were observed in various grades of OSCC. The other demographic details of these 22 cases are presented in Table 1. Due to this frequent observation at the surgical margins of OSCC-OSMF, we speculated that this could be a good histopathological predictive marker of malignant transformation in OSMF cases.

Fig. 1.

Photomicrograph of mucosal surgical margin associated with oral squamous cell carcinoma in the background of oral submucous fibrosis showing atrophic epithelium (black arrow) and dilated vascular spaces (white arrow) (A and B). The vascular spaces are surrounded by fibrosis (red arrow) associated with oral submucous fibrosis (C and D). (Hematoxylin and Eosin stain; Total magnification: 100x [A & B] and 400x[C & D]).

Table 1.

Demographic details of the OSCC-OSMF cases which showed frank and conspicuous vascular spaces at the mucosal margins.

Parameter	Sub-parameters	n
Number	22	–
Age	Range	32–80 years
	Mean	56.63 ​± ​13.1 years
Gender	Male	20 (90.9%)
	Female	2 (9.09%)
Site	Gingivo-buccal complex	19 (86.3%)
	Alveolar mucosa	2 (9.09%)
	Buccal mucosa	1 (4.5%)
Mouth opening	19.59 ​± ​6.2	–
TNM stage	II	1 (4.5%)
	IV	21 (95.4%)
Grade	Well differentiated	11 (50%)
	Moderately differentiated	10 (45.5%)
	Poorly differentiated	1 (4.5%)
Vascular spaces/HPF	7.31 ​± ​4.88	–

There are contrasting views about angiogenesis in OSMF. Our recent study has shown a statistically significant increase in neo-angiogenesis (CD105) in OSCC-OSMF cases as compared to OSMF cases.⁴ However, this type of angiogenesis in OSMF is always reported as small-sized vascular spaces or budding of endothelial capillaries. Moreover, the capillaries are obliterated/compressed due to dense fibrosis in the stroma and are not readily noticeable during the histopathological examination.⁵ In contrast, we observed extremely large, dilated and conspicuous vascular spaces at the surgical margins of OSCC-OSMF cases. To the best of our knowledge, to date, there is no report on the nature of vasculature at mucosal surgical margins of OSCC-OSMF. Hence, future studies are recommended in this direction to further authenticate the aforementioned proposition.

Nutritional demand in cancer cells increases many folds during malignant transformation.⁶ In OSCC-OSMF, the carcinogenesis might be initiated by chemical carcinogens in betel quid and mechanotransduction associated with the matrix stiffness.⁷ To further support the carcinogenesis in terms of nutritional demand, there could be a surge in the angiogenesis process. Since dense fibrosis is the main hindrance for the percolation of nutrients down to the transformed cells, the vascular spaces could have enlarged and dilated to meet the increased demand. Thus, this feature could be envisaged as a potential predictive biomarker for malignant transformation in OSMF patients. However, in the present observations, the samples were surgical margins and hence the direct peripheral effect of the primary tumor on causation of frank and conspicuous angiogenesis at those margins cannot be ignored.

Dense fibrosis also leads to a shortage of oxygen supply to the transformed cells. Hypoxia and HIF-1 α (Hypoxia-inducible factor 1- α) which evoke angiogenesis are considered to be one of the many factors triggering the malignant transformation.⁸ An extreme condition of hypoxia in OSMF could lead to dilatation of blood vessels to meet the demand of oxygen supply to the transforming cells. Thus, enlarged blood vessels in a hypoxic environment of OSMF depict the increased need of the transforming cells, which eventually leads to malignancy. Angiogenesis and such effects on the vascular spaces in the background of hypoxia require attention in future studies.

In conclusion, we proposed conspicuous and frank dilated vascular spaces as a marker of malignant transformation in oral submucous fibrosis. However, future studies on larger sample size as well as cohort studies on OSMF are needed for further authentication. If proved, this feature can be used for monitoring the disease progression and determining a follow-up protocol in OSMF patients. By this virtue, early detection of OSCC would also be possible leading to improved prognosis and better quality of life.

Funding source

The authors received no specific funding for this work.

Declaration of competing interest

All the authors associated with the present manuscript declared no potential conflict of interest with respect to the research, authorship, and/or publication of this article.