Prognostic significance of tumour budding in Merkel cell carcinoma

Prognostic factors in Merkel cell carcinoma (MCC) are scarce. Tumour budding (TB) has been shown to have a prognostic role in different cancers but has not been explored in MCC. We aimed to determine if TB influences survival in MCC.

We performed a retrospective evaluation of 45 cases of MCC in a cancer centre. This included a survival analysis involving TB in patients with MCC, and we searched for variables associated with TB.

The mean age of the patients was 69 years. Histologically, the average Breslow was 11.36 mm, and the mean mitotic rate was 31.9 mitoses/mm2. The diagnosis was made in clinical stages I and II in 40% of cases, 22.2% in stage III, and 37.8% in stage IV. Tumour budding was low (< 5 buds/0.785 mm2) in 44.4% of cases and high (> 10 buds/0.785 mm2) in 24.4%. There were no clinical or pathological features associated with high TB. Among the prognostic factors for 5-year survival, we found that tumour size and clinical stage were statistically associated with survival (p = 0.031 and 0.021), but TB was not.

No clinical or pathological characteristics of MCC are associated with any degree of TB. Tumour budding does not influence overall survival.