Differences in the vascular patterns of basal and squamous cell skin carcinomas explain their differences in clinical behaviour

Tumour angiogenesis is essential for tumour growth and appears to play an important role both at the transition from hyperplasia to invasive growth and at a late stage in the dissemination process. Basal cell carcinomas (BCCs) and trichoepitheliomas (TEs) are related tumours that share the properties of invasive growth but without the capacity to metastasize. Squamous cell carcinomas (SCCs) of the skin are derived from a similar cell type and they have both invasive and metastatic potential. The aim of this study was to investigate whether the behaviour of these tumours could be explained by differences in their microvasculature. The study looked both qualitatively and quantitatively at the microvasculature of BCCs (n=50) and TEs (n=33) and compared them with normal skin (n=6) and with SCCs of the skin (n=22). Vessel counts were performed using a standard graticule count method after immunohistochemical staining for CD31. Counts were made of blood vessels in the stroma surrounding the tumour and also for vessels in the body of the tumour. The stromal counts for all the tumour groups differed significantly from normal skin. The SCC counts differed significantly from the counts for the BCCs and TEs. There was no significant difference between the counts for different subtypes of BCC or TE groups. While vessels could be found in the body of the SCCs, none was seen in the nodular BCC or the TE groups. There was no correlation between the vascular density and the depth of invasion. Overall, invasive growth correlated with an angiogenic response in the stroma, while metastatic potential correlated with microvessels being present in the body of the tumour.