Acanthosis nigricans

Background

Normal dermal anatomy.

Dermatology Nomenclature

Small lesions (<0.5cm)

Name	Raised/Palpable	Fluid-Filled	Other Description	Diagram
Macule	No	None	flat, cirumscribed, colored
Papule	Yes	None	Solid
Vesicle	Yes	Clear
Pustule	Yes	Pus	Leukocytes or keratin

Large lesions (>0.5cm)

Name	Raised/Palpable	Fluid-Filled	Other Description	Diagram
Patch	No	None	Large macule (flat, colored)
Plaque	Yes	None	Superficially raised, circumscribed solid area
Nodule	Yes	None	Distinct large papule
Bulla	Yes	Clear	Large vesicle/blister or exposed epidermal layer
Wheal	Yes	Edema	Firm and edema of dermis

Other

Ulcer, fissue, and erosion

• Eschar
• Fissure/erosion/ulcer
• Necrotizing rashes
• Multiple forms, but malignant acanthosis nigricans is most important
  • Most commonly associated with colonic adenocarcinoma, gastric cancer, ovarian cancer
  • Also associated with other dermal manifestations of internal cancers
• Associated with GI and GU malignancies, which may have concomitant weight loss
• Non malignant form may be associated with endocrine abnormalities, such as insulin resistance

Clinical Features

Malignant acanthosis nigricans secondary to ovarian cancer

• Hyperpigmented, velvety
• Plaques
• Most commonly intertriginous areas, posterior neck
• May have concurrent acrochordons, skin tags

Differential Diagnosis

Dark raised skin lesions

• Acanthosis nigricans
• Kaposi's sarcoma
• Melanoma
• Nevus
• Seborrheic keratosis

Evaluation

Diagnosis

• Red flags for malignant acanthosis nigricans:
  • Oral involvement (up to 50%)
  • Rapid appearance of lesions
  • Extensive involvement
  • Older adult
  • Unexplained weight loss
  • Lesions in atypical sites such as palms/soles, mucous membranes

See Also

• Seborrheic keratosis
• Dark raised skin lesions

References

• Schwarzenberger K, Callen JP. Chapter 53: Dermatologic manifestations in patients with systemic disease. In: Bolognia JL,‎ Schaffer JV,‎ Cerroni L, eds. Dermatology. 4th ed. Philadelphia, PA: Elsevier; 2017:820.