Which histologic findings are characteristic of necrobiosis lipoidica?

Updated: Mar 06, 2020
  • Author: Cheryl J Barnes, MD; Chief Editor: George T Griffing, MD  more...
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Answer

Histopathologically, necrobiosis lipoidica presents with interstitial and palisaded granulomas that involve the subcutaneous tissue and dermis. At low magnification, lesions of necrobiosis lipoidica have a very characteristic appearance. The granulomas are arranged in a tierlike (layered) fashion and are admixed with areas of collagen degeneration. The granulomas are composed of histiocytes (some of them multinucleated), lymphocytes, occasional plasma cells, and eosinophils. Reduction in the number of intradermal nerves is an additional feature of necrobiosis lipoidica.

The main findings on histopathology are thickening of the blood vessel walls and endothelial cell swelling found in the middle to deep dermis, characteristics shared with diabetic microangiopathy.

Direct immunofluorescence microscopy of necrobiosis lipoidica has demonstrated immunoglobulin M (IgM), IgA, C3, and fibrinogen in the blood vessels, which cause the vascular thickening. [5] In nondiabetic patients with necrobiosis lipoidica, the vascular changes are not as prominent.

A study by Ramadan et al indicated that dermoscopy can aid in differentiating cutaneous sarcoidosis from necrobiotic granulomas, even in patients who have undergone treatment with systemic steroids. The investigators found that although some dermoscopic features overlap between these conditions, cutaneous sarcoidosis differs dermoscopically from necrobiotic granulomas by its association with a pink homogenous background, translucent orange regions, white scarlike depigmentation, and fine white scales. Moreover, a significant association was found between necrobiotic granulomas and a mixed pink, white, and yellowish background. In addition, features distinguished in patients treated with systemic steroids did not significantly vary from those found in untreated patients. [14]


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