Acral Lentiginous Melanoma - Beware of the Pigmented Lesion on the Asian Foot
BULLETIN FOR MEDICAL PRACTITIONERS
Dr Tan Boon Tiong, Assistant Registrar
Dr Chua Sze Hon, Consultant
National Skin Centre
Introduction
There are a few conditions that present as a pigmented lesion on a foot - acral lentiginous melanoma being one of them. In Asians, the presentation of melanoma is slightly different from that seen in the Caucasian population. This case report highlights a common presentation of melanoma in Singapore.
Case Report
The patient, an 88-year old Chinese male who was a retired school teacher, presented to the National Skin Centre (NSC) via a polyclinic referral with a 3-month history of an enlarging pigmented ulcer on his right sole. There was no trauma or mole prior to the ulcer. He did not have any personal history of dysplastic nevi, excessive sun exposure or immunosuppression. There was no family history of any malignancy of note. The ulcer was initially treated with antiseptic creams by the primary level physician without any formal diagnosis. As the ulcer failed to respond to the topical therapy given and was progressively enlarging in size, he was referred to NSC for further evaluation and management.
Examination revealed an otherwise healthy elderly gentleman with a shallow ulcer measuring 21mm by 18mm on the lateral margin of the right mid-sole in the weight bearing area. The ulcer had a pigmented base with slightly raised edges (Fig. 1). There were no palpable regional lymph nodes, hepato-splenomegaly or any clinically suspicious melanocytic nevi on systemic examination.
An skin biopsy was performed. Histology revealed acanthosis with atypical malignant cells of irregular hyperchromatic nuclei and prominent nucleoli lining the basal layer with occasional nests. The clinico-pathological picture was that of an acral lentiginous melanoma (ALM). He was subsequently referred to the oncology surgeons at the National Cancer Centre, where he underwent wide local excision of the lesion.
Discussion
The differential diagnosis of a pigmented lesion on the sole includes benign lesions such as lentigo simplex and melanocytic nevus; superficial fungal infection e.g. tinea nigra and malignant lesions such as pigmented basal cell carcinoma and acral lentiginous melanoma (ALM). ALM must always be considered and excluded in an Asian patient presenting with a suspicious pigmented lesion on the acral parts of the body. If in doubt, a skin biopsy for histological diagnosis should be performed early.
Melanoma is one of the most lethal skin cancers. Fortunately, it is not a common skin malignancy in Singapore. The prevalence is about 0.4 per 100,000 for males and 0.5 per 100,000 for females 1 . The majority of the lesions are on the foot. The peak age of presentation is the 7th decade with a mean of 59. A recent review of melanoma cases seen in NSC 2 showed 41% being ALMs and 41% nodular melanomas. Common clinical presentation of ALM includes a non-healing pigmented ulcer or a bleeding pigmented nodule. The sole, thumb and the big toe 3,4 are most commonly affected. ALM has a relatively poorer prognosis; this being related to a later presentation and correlating with a thicker lesion with more advanced Breslow and Clarks prognostic classification 5 .
The preponderance of ALM in the Asians is due to the lesser risk of melanoma formation in other body sites. Melanoma in Caucasians tends to be in the areas of intermittent intense sun exposure e.g. on the upper back, distal limbs and face. The type of melanoma in Caucasians is predominantly superficial spreading melanoma (70%) as opposed to ALM (10%)6 . The majority of melanomas seen in countries with strong awareness programs are usually thinner and associated with a better prognosis. In Singapore, the survey of melanoma patients revealed a poor awareness rate for the danger signs of melanoma; the referral pattern from primary care physicians also suggested a low rate of clinical suspicion in most cases 2 .
Prognosis of melanoma relates to the patient’s characteristics and presentation, where younger age, female, peripheral lesions (with the exception of acral tumor), the lack of lymph node involvement and ulceration having a better diagnosis. Histological prognosis involves the extent of depth invasion (Clark’s level) or tumor thickness (Breslow microstaging), presence of lymph node involvement and microscopic satellite invasion.
Treatment of all melanoma involves excision of the primary lesion with a 1cm margin for lesions less than 2mm 7 thick and wider if the thickness exceeds 1mm. The survival of patients with ALM has been reported to be as low as 35% in 5 years in Japan to as high as 71% in Germany 5,6 . Metastases have been reported to occur as late as 13 years after initial wide excision, suggesting that life-long follow-ups may be necessary. In some countries, sentinel lymph node biopsy for thicker lesions has been shown to be of important prognostic value. In advanced cases, selective excision of specific metastasis, hyperthermic regional limb perfusion with melphalan with IL-2 and interferon alpha treatment have been shown to be of beneficial palliative value. Currently, for advanced disease, there are new biochemotherapeutic agents and regimes that are being assessed; they include combination of IL-2 with chemotherapy, temozolomide, oral decarbazine along with various experimental melanoma vaccine 8 .
Conclusion
Melanoma, although uncommon in Singapore, deserves better public awareness among patients and primary health care physicians. Melanoma should be considered in all pigmented lesions especially if they occur in the acral areas. It is important to diagnose melanoma early as this has the greatest impact on survival after excision.
References
- Chia KS, Seow A, Lee H P, Shanmugaratnam K. Cancer incidence in Singapore 1993-97. Singapore. Singapore Cancer registry 2000: report no.5.
- Tan E, Chua SH, Lim J, Goh CL. Malignant melanoma seen in a tertiary dermatological centre, Singapore. Annals, Acad of Med Singapore 2001:30(4) 414-8.
- Seiji M. Takematsu H. Hosokawa M. Obata M. Acral melanoma in Japan. Journal of Investigative Dermatology 1983 Jun:80 Suppl:56s-60s.
- Chen YJ. Wu CY. Chen JT. Shen JL. Clinicopathologic analysis of malignant melanoma in Taiwan. J Am Acad Derm 1999, 41(6):945-9.
- Kuchelmeister C. Schaumburg-Lever G. Garbe C. Acral cutaneous melanoma in Caucasians: clinical features, histopathology and prognosis in 112 patients. Br Journal of Derm 2000, 143(2):275-80.
- Kato T. Suetake T. Tabata N. Takahashi K. Tagami H. Epidemiology and prognosis of plantar melanoma in 62 Japanese patients over a 28-year period. Int Journal of Derm 1999, 38(7):515-9.
- Kanzler M. Mrag-Gernhard S. Primary cutaneous malignant melanoma and its precursor lesions: Diagnostic and therapeutic overview JADD 2001, 45(2):260-276.
- Reintgen D, Cruise C and Atkins M. Cut. malignant melanoma. Clinics in Dermatology 2001:19,253-9.
DEDICATED TO EXCELLENCE IN DERMATOLOGY
By National Skin Centre (Singapore)
Copyright (C) 1995 - National Skin Centre (Singapore)
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