A 52-year-old man from Mumbai presents with a pigmented lesion on his back that has been enlarging over 6 months. Dermoscopy shows asymmetry, irregular borders, and mixed colors. Excision biopsy confirms cutaneous melanoma with a Breslow thickness of 2.8 mm and no ulceration. Which is the most common site of primary cutaneous melanoma in Indian patients?

Explanation

## Most Common Site of Primary Cutaneous Melanoma in Indian Patients ### Ethnic Variation in Melanoma Site Distribution **Key Point:** In Indian (and other Asian/darker-skinned) populations, the most common site of primary cutaneous melanoma is the **acral region — palms, soles, and subungual areas** — corresponding to the acral lentiginous melanoma (ALM) subtype. This contrasts sharply with Caucasian populations, where the trunk (back/chest) and lower extremities predominate. ### Site Distribution: Indians vs. Caucasians | Site | Frequency in Indians | Frequency in Caucasians | |------|----------------------|-------------------------| | Palms, soles, subungual (acral) | 40–60% | 2–5% | | Back and trunk | 15–20% | 25–30% | | Lower extremity | 15–20% | 35–40% (women) | | Head and neck | 10–15% | 15–20% | **High-Yield:** Multiple Indian studies (including data from AIIMS, Tata Memorial, and regional cancer registries) consistently show that acral lentiginous melanoma accounts for the largest proportion of melanomas in Indian patients. This is a well-established epidemiological fact cited in Indian dermatology textbooks (Valia & Valia, IADVL Textbook of Dermatology) and corroborated by global reviews of melanoma in non-Caucasian populations (Cormier et al.; Bradford 2009, *Arch Dermatol*). ### Why Acral Melanoma Predominates in Indians - Acral sites lack the photoprotective effect of overlying hair follicles and have a distinct melanocyte biology - UV radiation is **not** the primary driver of ALM (unlike superficial spreading melanoma in Caucasians), explaining why sun-exposed trunk is not the dominant site - Genetic and molecular differences (e.g., KIT mutations more common in ALM) underlie this ethnic predilection ### Clinical Pearl **Clinical Pearl:** Because acral melanoma is the most common type in Indians, clinicians must carefully examine the soles, palms, and nail beds during skin cancer screening — areas often overlooked in routine examination. Subungual melanoma may mimic onychomycosis or subungual hematoma, leading to diagnostic delays. **Mnemonic:** In **I**ndians — **A**cral is **A**lways first (Palms, Soles, Subungual). ### Relevance to This Case The patient in this vignette has a trunk melanoma (Breslow 2.8 mm, no ulceration → Stage IIB per AJCC 8th edition), which, while clinically significant, represents a less typical site for Indian patients. Awareness of the predominance of acral melanoma in this population is essential for population-level screening strategies. *Reference: IADVL Textbook of Dermatology, 4th ed.; Bradford PT. Arch Dermatol. 2009;145(4):427–434.*