Expression of insulin-like growth factor-I receptor in primary cutaneous carcinomas

Insulin-like growth factor-I (IGF-I) is the principal mediator of growth hormone, exerting its effects through binding of the insulin-like growth factor-I receptor (IGF-IR). Post-receptor activation leads to the production of transcription factors involved in cell proliferation, differentiation, transformation, and survival. Data indicate that IGF-IR is involved in tumorigenesis. To our knowledge, this receptor has not been previously studied in primary cutaneous carcinomas.

Twenty-five cases of primary cutaneous carcinomas consisting of three keratoacanthoma-type squamous cell carcinomas (KAs), two squamous cell carcinomas in situ (SCCs in situ), eight squamous cell carcinomas (SCCs), three conventional basal cell carcinomas (BCCs), two morpheaform basal cell carcinomas (M-BCCs), and seven Merkel cell carcinomas (MCCs) were analyzed for IGF-IR immunohistochemical expression using IGF-IR mouse monoclonal antibody (dilution 1 : 50) using the avidin-biotin-peroxidase complex method.

Normal epidermis was negative for IGF-IR expression. Normal eccrine glands and outer root sheath strongly expressed IGF-IR. All KAs, SCCs in situ, SCCs, and BCCs were negative for IGF-IR expression. Six of seven (86%) of the MCCs stained with IGF-IR strongly, showing cell membrane accentuation and a perinuclear dot-like pattern.

The data suggest that IGF-IR immunopositivity in MCCs might constitute a diagnostic tool in discriminating between SCCs and BCCs. Although the possible pathogenic significance of the perinuclear dot-like staining pattern observed in these neoplasms is unknown, its pattern is similar to what has been previously described with cytokeratin-20 immunostaining.