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| Fig. 37.6 Acanthosis nigricans. Velvety hyperpigmented lesions of the neck, axilla, and knuckles in an obese individual. (Courtesy of the Fitzsimons Army Medical Center teaching files.) |
AN may be caused by endocrine disorders (insulin resistance), obesity (Fig. 37-6), medications, genetic abnormalities, or underlying cancer. However, the sudden onset of widespread AN in an adult with weight loss should suggest an underlying malignancy. Many different cancers have been reported with “malignant” AN, but almost 60% of patients have adenocarcinoma of the stomach. In most of these cases, AN develops when the tumor is in an advanced stage. One third of patients have AN before, one third during, and one third present after the discovery of the internal malignancy. In some cases, successful resection of the adenocarcinoma leads to regression of the AN. Gastric adenocarcinoma secrete TNF-α, which inevitably stimulates the epidermal growth factor (EGF) receptor to cause proliferation of keratinocytes.
Malignant AN initially presents abruptly as a darkening and thickening of the skin, occasionally with pruritus. This morphology progresses into symmetrical hyperpigmented, velvety plaques that occur most commonly around the posterior neck, axilla, and groin. Treatment for malignant AN is correction of the underlying pathology.
“Tripe palms” is another form of AN, and refers to AN of the palms in which there is a velvety furrowing of the palmar surfaces. It is almost always associated with internal malignancy. When Tripe palms occurs in the absence of AN, squamous cell carcinoma should be suspected. The sign of Leser-Trélat (increased numbers or the explosive onset of seborrheic keratoses) can also be associated with AN and tripe palms and it stems from the same circulating epidermal growth factors. Leser- Trélat may also be seen with tumors of the female reproductive tract and lymphoproliferative disorders.
Thiers BH, Sahn RE, Callen JP: Cutaneous manifestations of internal malignancy,
CA Cancer J Clin 59(2):85–86, 2009. (Triple palms, Leser-Tréla
