DP15: Rates of perineural invasion in cutaneous squamous cell carcinoma in an Irish cohort of renal transplant recipients versus immunocompetent patients

Claire Doyle, Kira Casey and Siona Ni Raghallaigh

Beaumont Hosptial, Dublin, Ireland

Cutaneous squamous cell carcinoma (cSCC) is characterized by the malignant proliferation of epidermal keratinocytes. High-risk prognostic features that predict both local recurrence and distant metastases include tumour diameter (≥ 2 cm) depth of invasion (≥ 6 mm), invasion beyond subcutaneous fat, tumour site (ear and lip), poorly differentiated tumours, lymphovascular invasion, perineural invasion (PNI) and immunosuppression. Rates of perineural invasion observed in cSCC are between 2·4% and 14%. PNI in cSCC is seen more frequently in males, recurrent tumours, location on the face, poorly differentiated histology and deep tumour extension. It has been reported in the literature that there is an increased rate of PNI in the cSCCs of transplant patients. We report our experience in an Irish cohort. The histological features of 45 cSCCs in renal transplant recipients (RTRs) were compared with 46 cSCCs in immunocompetent patients. Mean age of the RTR cohort was 70 years vs. 77 for the immunocompetent cohort. Seventy-one per cent (n = 32/45) of the RTR cohort were male vs. 59% (n = 28/46) of the nontransplant cohort. Ninety-one per cent (n = 41/45) of the RTR had a prior keratinocyte cancer vs. 26% (n = 12/46) of the immunocompetent patients. Mean tumour diameter was 14·5 mm (range 2–40) for the RTR cohort and 15 mm (range 4–35) in the nontransplant group. Histological features of the cSCCs in the RTR cohort revealed that 31% (n = 14/45) were well differentiated, 51% (n = 23/45) cSCCs were moderately differentiated and 18% (n = 8/45) were poorly differentiated. Twenty per cent (n = 9/45) had evidence of PNI. Two per cent (n = 1/45) had evidence of lymphovascular invasion. In the immunocompetent cohort, 35% (n = 16/46) were well differentiated, 50% (n = 23/46) were moderately differentiated and 15% (n = 7/46) were poorly differentiated. Four per cent (n = 2/46) had evidence of PNI. No patients had evidence of lymphovascular invasion. Clinical follow-up was for a time period of 3 years after diagnosis. In the RTR cohort with PNI, 33% (n = 3/9) had evidence of local tumour recurrence treated successfully with further excision. Thirty-three per cent (n = 3/9) had metastatic cSCC with 11% (n = 1/9) dying from metastatic cSCC. In the immunocompetent cohort with PNI 0% had local tumour recurrence. Fifty per cent (n = 1/2) had metastases treated with completion neck dissection. There were no deaths in the immunocompetent cohort. This small cohort study shows that rates of PNI were higher in cSCCs in Irish RTRs than in an immunocompetent cohort. In the subgroup of RTRs and PNI the tumours were more locally aggressive and more likely to metastasize. In the event of cSCC metastases, it was more likely to be fatal in the RTR cohort vs. the immunocompetent cohort. Our findings are in keeping with published cohorts from other populations. It is important to consider that patients with both PNI and transplant status will likely need more intensive clinical follow-up due to higher rates of local recurrence, distant metastases and tumour-specific death.