Immunoexpression of Bcl-x in squamous cell carcinoma and keratoacanthoma: differences in pattern and correlation with...

Bcl-x is an important anti-apoptotic member of the Bcl-2 family. The aim was to determine its immunoexpression in cutaneous squamous cell carcinoma (SCC) and keratoacanthoma (KA).

Sixteen SCCs and 39 KAs were investigated by Bcl-x immunohistochemistry. Bcl-x immunoreactivity was mostly diffuse in SCC (75% of cases), whereas that in KA was typically confined to the mid-to-upper spinous keratinocytes (95%) (P < 0.0001). There was a trend for SCC to have a higher likelihood of immunopositivity (weighted staining score > or =6 of 12) compared with KA (88% versus 59%, P = 0.058). Twenty-nine per cent of regressing KA had immunopositivity, whereas 47% and 82% of its stable and proliferating counterparts, respectively, had equivalent positivity (P = 0.024).

These results provide some insight into the pathobiology of SCC and KA. The generally diffuse and stronger Bcl-x immunoreactivity in SCC suggests that the protein contributes to the survival advantage and aggressiveness of the tumour. In KA, the preferential reactivity of the mid-to-upper neoplastic keratinocytes can plausibly be explained by such differentiated cells attempting to prolong their existence under rapidly evolving circumstances, whereas the reduced reactivity in regressing KA is consistent with the end stage of the tumour.