From one of the best medical books in the last 40 years or so in my opinion!

Orient, Jane M.. Sapira’s Art and Science of Bedside Diagnosis (Kindle Locations 6737-6754). Lippincot (Wolters Kluwer Health). Kindle Edition.

If you are a medical professional and still working then consider bying this book.

Malignant Melanoma

Malignant melanomas are said to be differentiable from other lesions by examining them for red color (a sign of immunologic reactivity against a “foreign” substance), white color (amelanotic sites indicating depigmentation due to tumor regression), or blue color (said to be peculiar to some melanomas but also occurring in the benign blue nevus). Whatever the correct pathophysiologic explanations for these colors, the clinical significance is correct; they are flags for a possible malignancy. The mnemonic might be the colors of the flags of the US, the UK, New Zealand, or Australia. [my addition: The flag of the Netherlands [Holland] image.png [The writer probably never visited Holland]

Nevertheless, malignant melanoma can be in varying shades of brown. Also, if you see black or thundercloud gray, you must think melanoma. Malignant pigmented tumors tend to be asymmetric and to have a notch. Malignant melanomas are usually larger than a pencil eraser when first diagnosed. It is obviously desirable, however, to diagnose them sooner. The ABCD rule for diagnosing a possible melanoma is A for asymmetry, B for irregular border, C for variation in color, and D for diameter greater than 6 mm. Dr Danehower suggests not waiting for the D; he has diagnosed many melanomas less than 6 mm in size. Stretching a suspicious nevus between two fingers, especially after coating it with a few drops of soap or oil, may make erythema and irregular pigmentation more obvious. It is also important to use adequate lighting, such as direct sunlight or a strong incandescent or quartz halogen light. Fluorescent light hinders diagnostic accuracy because its discontinuous spectrum turns the pink hues of dysplastic nevi to a dull gray (Crutcher and Cohen, 1990). The incidence of malignant melanoma has a complicated relationship with exposure to sunlight (vide infra), but these cancers can occur on any part of the skin or mucous membranes. The plantar surface is a common site in nonwhite persons (Rogers and Gibson, 1997).

Orient, Jane M.. Sapira’s Art and Science of Bedside Diagnosis (Kindle Locations 6737-6754). Lippincot (Wolters Kluwer Health). Kindle Editio