Acral Melanoma in Chinese: A Clinicopathological and Prognostic Study of 142 cases

Abstract

Acral melanoma (AM), as a peculiar subgroup of melanoma, is rare in Caucasians but has higher incidence in Asians. Large series of study on AM with clinicopathological features and prognostic factors is still limited, especially in Asian population. We retrospectively collected clinical, pathological and follow-up data of 142 AM cases. All patients were Chinese, with the age ranging from 24 to 87 years (mean 62.0; median 62.0). The Breslow thickness of primary lesions ranged from 0.6 to 16.3 mm (mean 4.9; median 3.7). 85.9% of the patients had acral lentiginous histologic subtype. Plantar was the most frequently involved site, followed by heels. Statistically, duration of the lesion before diagnosis (≤2.5 years), Breslow thickness >4.0 mm (T4), high mitotic index (>15 mm(-2)), presence of vascular invasion, regional lymph node metastasis at diagnosis and pathologic stage (II/III/IV) were found to be independent prognostic factors in both univariate and multivariate analyses. The prognosis of AM in Chinese is extremely poor. Our 5- and 10-year disease-specific survival (DSS) rates were 53.3% and 27.4%, respectively. Therefore, AM in Asians represents a more biologically aggressive melanoma subtype and is thought to carry a worse prognosis when compared with other races or cutaneous melanomas in other anatomic sites.

Figure 1

(a) AM on the heel, showing a rapidly expanding plaque with irregular margins and ulceration. (b) AM on the plantar, the tumorigenic vertical growth phase nodule is present within a background pigmented macule. (c) AM on the plantar, showing foci of satellites (arrows) discontinuous from the main irregular and pigmented lesion. (d) Achromic melanoma on the heel resembling granuloma pyogenium. (e) SUM showing pigmented strip on the index finger. (f) SUM on the little finger, thickening, splitting and destruction of the nail plate. (g) SUM on the thumb, spreading to the skin of the digit proximally, laterally, and distally (Hutchinson sign). (h) SUM on the great toe, the entire nail matrix and nail bed are occupied by irregular pigmented mass involving the ungual fold and periungual skin.

Figure 2

(a) ALM in situ. Lentiginous proliferation of atypical melanocytes along the basal epidermis (original magnification ×100). (b) ALM with vertical growth phase, Clark level IV (original magnification ×100). (c) Ulceration (original magnification ×100). (d) Scattered mitoses in dermal lesion of melanoma (arrows) (original magnification ×400). (e) Vascular invasion by melanoma cells in septa of adipose tissue (original magnification ×200). (f) Melanoma metastasis with prominent pigment in regional lymph node (original magnification ×40).

Figure 3. Kaplan-Meier analyses of DSS for the entire group of patients according to different stratums by prognostic factors.

(a) Duration of the lesion. (b) Breslow thickness. (c) Clark level. (d) Ulceration status. (e) Mitotic rate. (f) Vascular invasion. (g) Regional lymph node status at diagnosis. (h) Pathologic stage.