What is malignant acanthosis nigricans (AN)?

Updated: Oct 14, 2020
  • Author: Jason H Miller, MD; Chief Editor: William D James, MD  more...
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Malignant acanthosis nigricans, which is associated with internal malignancy, is the most worrisome of the variants of acanthosis nigricans because the underlying neoplasm is often an aggressive cancer (see the Table in Pathophysiology).

Acanthosis nigricans has been reported with many kinds of cancer, but, by far, the most common underlying malignancy is an adenocarcinoma of gastrointestinal origin, usually a gastric adenocarcinoma. In an early study of 191 patients with malignant acanthosis nigricans, 92% had an underlying abdominal cancer, of which 69% were gastric. Another study reported 94 cases of malignant acanthosis nigricans, of which 61% were secondary to a gastric neoplasm.

Malignant acanthosis nigricans in pediatric patients has been described with gastric adenocarcinoma, Wilms tumor, and osteogenic sarcoma. [1]

In 25-50% of cases of malignant acanthosis nigricans, the oral cavity is involved. The tongue and the lips most commonly are affected, with elongation of the filiform papillae on the dorsal and lateral surfaces of the tongue and multiple papillary lesions appearing on the commissures of the lips. Oral lesions of acanthosis nigricans seldom are pigmented.

Tripe palms may show altered dermatoglyphics due to alteration of epidermal rete ridges

Malignant acanthosis nigricans is clinically indistinguishable from the benign forms; however, one must be more suspicious if the lesions arise rapidly, are more extensive, are symptomatic, or are in atypical locations.

Regression of acanthosis nigricans has been seen with treatment of the underlying malignancy, and reappearance may suggest recurrence or metastasis of the primary tumor.

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