Melanoma — Subtypes and Prognostic Factors

A 45-year-old man with a history of multiple atypical nevi presents with a 1.2 cm dark brown lesion on his back with irregular borders, color variegation (brown, black, and red), and asymmetry. Dermoscopy reveals a multicomponent pattern with peripheral globules and central homogeneous area. Excision biopsy shows a lesion with Breslow thickness of 1.8 mm, Clark level IV invasion, with 3 mitotic figures per mm², and no ulceration. Which of the following is the most accurate prognostic indicator for this patient's melanoma?

A 58-year-old woman with a 10-year history of vitiligo presents with a solitary, rapidly enlarging, darkly pigmented nodule on the dorsal surface of her right foot. Dermoscopy reveals a polymorphous vascular pattern with irregular dots and globules. Histopathology shows nests of epithelioid melanocytes with moderate nuclear pleomorphism, scattered mitotic figures (8 per 10 high-power fields), and a brisk lymphocytic infiltrate at the base. The lesion measures 1.2 cm in maximum dimension. Which of the following is the single most important adverse prognostic factor in this case?

A 58-year-old man presents with a 2-cm dark brown nodule on his left shoulder that has been present for 8 months. He reports recent rapid growth and bleeding. On examination, the lesion is asymmetrical, has irregular borders, and shows variegated pigmentation with areas of black, brown, and red. Dermoscopy reveals a blue-grey veil and atypical vascular patterns. Excision biopsy shows invasion into the subcutaneous fat with a Breslow thickness of 3.2 mm and 8 mitoses per mm². Clark level is IV. What is the most likely melanoma subtype?

A 72-year-old woman with a 20-year history of sun exposure presents with a 1.5-cm tan-brown macule with irregular borders on her left temple. The lesion has been present for 5 years and has slowly enlarged. Dermoscopy shows asymmetrical pigmentation with a rhomboidal pattern and follicular involvement. Excision biopsy reveals atypical melanocytes confined to the epidermis and superficial dermis (Clark level II) with a Breslow thickness of 0.8 mm. Mitotic rate is <1/mm². What is the most likely melanoma subtype, and what is the key prognostic implication?

A 52-year-old man presents with a 1.5 cm dark brown lesion on his back with irregular borders and color variation. Clinical examination suggests melanoma. Which investigation is the gold standard for confirming the diagnosis and determining histological subtype?