A 52-year-old man presents with a pigmented lesion on his back that has been growing over the past 6 months. Dermoscopy and biopsy confirm 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 Cutaneous Melanoma in Indian Patients **Key Point:** In Indian (and other Asian/dark-skinned) populations, **acral lentiginous melanoma (ALM)** is the predominant subtype, occurring on the palms, soles, and subungual regions — making the **lower extremity (plantar surface/sole)** the most common site of primary cutaneous melanoma. ### Anatomical Distribution in Indian Patients | Site | Frequency | Notes | |------|-----------|-------| | Lower extremity (sole/plantar) | ~40–60% | **Most common** — ALM subtype predominates | | Upper extremity (palm/subungual) | ~15–25% | ALM on hands/nails | | Head and neck | ~10–15% | Lentigo maligna type; older patients | | Back/Trunk | Less common than in Caucasians | Most common in Caucasian populations, NOT in Indians | **Clinical Pearl:** Unlike Caucasian populations where superficial spreading melanoma on the trunk/back predominates, Indian and other pigmented-skin populations have a higher proportion of acral lentiginous melanoma (ALM). ALM arises on non-hair-bearing glabrous skin — predominantly the plantar foot — and is not related to UV exposure. This explains why the lower extremity is the most common site in Indians. **High-Yield:** The distribution of melanoma subtypes differs significantly by ethnicity: - **Caucasians:** Superficial spreading melanoma on trunk/back is most common - **Indians/Asians/Africans:** Acral lentiginous melanoma on lower extremity (sole) is most common **Mnemonic:** In **dark-skinned** populations — think **"Sole Survivor"** — the sole of the foot is the most common melanoma site. ### Why Lower Extremity is Most Common in Indians 1. ALM is the dominant subtype in Indian patients (accounts for ~50–70% of melanomas in Indians vs. ~5% in Caucasians) 2. ALM preferentially affects the plantar surface of the foot 3. Not UV-dependent — occurs in non-sun-exposed glabrous skin 4. Often diagnosed late due to location and lack of awareness [cite: Fitzpatrick's Dermatology 9e; Robbins & Cotran Pathologic Basis of Disease 10e Ch 25; ICMR epidemiological data on melanoma in India]