Clinicopathological features and prognosis of patients with de novo versus nevus-associated melanoma in Taiwan

Abstract

Studies surveying melanomas associated with melanocytic nevi in Asia are rare. In this study, we examined whether nevus-associated melanomas differ from de novo melanomas in terms of their associations with clinical factors, histologic characteristics, and patient survival in Taiwan. Using data on cancer cases obtained from the Department of Pathology archives and the Cancer Registry of National Taiwan University Hospital, we conducted a retrospective analysis of 103 consecutive melanoma patients who were diagnosed between 2010 and 2015 and received follow-up through November 2016. Approximately 17.5% of the melanomas in question were associated with a nevus. In patients under 65 years of age, non-acral lentiginous melanomas were significantly associated with a higher percentage of nevus-associated melanomas. The superficial spreading subtype, younger patient age, thinner tumor, intermittent solar exposure, and early stage were significant predictors of a melanoma being histologically associated with a nevus. The appearance of a nevus associated with a melanoma predicted better recurrence-free survival compared with de novo melanomas. Although acral lentiginous melanomas (70.9%) constituted the most common histologic subtype, only 9.6% of the acral lentiginous melanomas were associated with a nevus. Furthermore, there was no statistically significant difference between the nevus-associated and de novo acral lentiginous melanomas with regard to clinicopathological factors and survival. In conclusion, nevus-associated melanomas were uncommon among acral lentiginous melanomas. Relatedly, because over half of all melanomas in Asians are acral lentiginous melanomas, Asians are less likely than Caucasians to have nevus-associated melanomas.

Fig 1. Superficial spreading melanoma arising from a nevus.

(A) A 63-year-old man presented with a 5 x 2.5 cm plaque on the left flank with irregular scalloped borders, mottled variegate color, large areas of regression, and a small nodule in the center. (B) Low-powered photomicrograph demonstrating a nodular lesion composed of tumor cells arranged in nests in the dermis with a Breslow thickness of 3 mm. Mitotic figures are numerous. Original magnification x 40. (C) Conventional dermal nevus nests can be noted adjacent to the tumor mass. Original magnification x 100. (D) High-powered photomicrograph reveals nests of tumor cells with vesicular nuclei and prominent nucleoli. Original magnification x 100. (E) Melanoma cells stained positive and nevus cells negative for HMB-45. Original magnification x 40. (F) Melanoma cells stained positive for Ki-67. Original magnification x 40.

Fig 2. Kaplan-Meier curves of survival for 103 primary melanoma patients.

No overall (A) and distant metastasis-free survival (B) differences were found between patients with de novo and nevus-associated melanomas (p = 0.058 and 0.062, respectively). (C) Patients with melanomas arising in association with a pre-existing nevus had better recurrence-free survival than those with de novo melanomas (p = 0.014).

Fig 3. Kaplan-Meier curves of survival for 73 patients with primary acral lentiginous melanomas.

No overall (A), distant metastasis-free survival (B), and recurrence-free survival (C) differences were found between patients with de novo and nevus-associated acral lentiginous melanomas (p = 0.168, 0.159, and 0.091, respectively, log rank test).