Characteristics of patients with melanoma with non‑melanoma skin cancer comorbidity: Practical implications based on a retrospective study.

The co-occurrence of melanoma and non-melanoma skin cancer (NMSC) can lead to increased morbidity. However, there has been limited research into the dermoscopic characteristics of melanomas and clinical factors during co-occurrence. A total of 264 patients with melanoma, including 63 with NMSC comorbidity, were enrolled in the present study to retrospectively analyse the coexistence of melanoma morphology, as determined by dermoscopic examination, pathological report, tumour location and clinically manifested risk factors. The frequency of solar lentiginosis (SL) was compared between 264 patients with melanoma and 233 patients with NMSC without melanoma. In 83.4% of cases, skin cancer occurred before or concomitantly with the melanoma. The leading indicators of comorbidity were age (median 70 years; P<0.0001) and SL on the trunk and arms (P<0.0001). Melanomas in patients with NMSC comorbidity were significantly more frequently located on the head and neck [P<0.001; Bonferroni adjusted P-value (P-adj.)<0.01], then on the trunk, but less frequently occurred on the lower limbs (P<0.05). The dermoscopic multicomponent asymmetric pattern was the predominant pattern in both groups. The most characteristic pattern in the NMSC group was facial melanoma (P<0.005; P-adj.<0.05); the spitzoid pattern (P<0.001; P-adj.<0.01) was rare. Dermoscopic regression was more common (P<0.001) in the NMSC group. Regression and the number of nevi were independent of age. Differences in the incidence of SL were evaluated based on the presence of melanoma (P<0.01) and in patients without melanoma based on the presence of squamous cell carcinoma (SCC; P<0.01), multiple basal cell carcinoma (P<0.0001) and multiple SCC (P<0.005). Patients with melanoma were 10 years younger on average compared with patients with NMSC (P<0.0001). The differentiation factors identified in the present study may improve the precision of dermoscopic examinations and potentially lead to modifications in the diagnostic workflow for patients with multiple NMSCs with comorbid melanoma.