Evidence based information
Written  by Dr. Sanjana V.B

[Medical editorial team head SIAHMSR]

Malignant acanthosis nigricans

   Acanthosis Nigricans  is a benign skin pigmentation disorder manifested as dark patch of skin with a thick, velvety texture. Dark, thick and velvety patches are usually found on skin folds and on areas like armpits, back of your neck, groin, elbows, face, knees, knuckles, and soles of the feet and underneath female breasts.

 Acanthosis nigricans appear as velvety hyper-pigmented patches with poorly defined borders on these areas. It is often a sign of underlying disease.  Acanthosis nigricans is strongly associated with pre-diabetes, insulin resistance, diabetes, polycystic ovarian syndrome, metabolic syndrome and obesity.

 Sometimes, acanthosis nigricans can be a warning sign of serious disease conditions such as cancers in a few percentages of people. It may be a paraneoplastic syndrome associated with  gastric adenocarcinoma  and other cancers. This is called as malignant acanthosis nigricans. Malignant acanthosis nigricans was first described in 1890 by Pollitzer (1891) and Janowsky (1891).

  It is considered as a warning sign of cancer although it is seen in less serious conditions also. Malignant Acanthosis nigricans is associated with gastrointestinal cancers and cancers of prostate, breast, and ovary. Lung cancer and lymphoma are also associated with acanthosis nigricans rarely. Malignant acanthosis nigricans may precede, accompany, or follow the onset of internal cancer and is manifested suddenly with itching [4].

How to diagnose Malignant  acanthosis nigricans?

 Acanthosis nigricans is diagnosed by clinical examination of the patient and confirmed with a skin biopsy. On biopsy, hyperkeratosis, leukocyte infiltration, epidermal folding, and melanocyte proliferation may be seen. Biopsy of acanthosis nigricans is not routinely done, but it is ordered in suspected cases of malignancy or cancers.

 As acanthosis nigricans can be associated with pre diabetes, diabetes, metabolic syndrome and polycystic ovarian syndrome etc. certain investigations like fasting blood sugar, hormonal assays & ultrasonography of pelvis are done.

Blood tests, endoscopy, or x-rays may be required to eliminate the prospects of diabetes or cancer.

 Measuring glycosylated hemoglobin is also recommended to rule out diabetes and insulin resistance.

Differential Diagnosis

·        Seborrhea

·         Tinea

·         Erythrasma

·         Candidiasis

·         Pellagra

·         Ichthyosis

·         Linear epidermal nevus

·         Granular parakeratosis

·         hyperpigmentation of Addison's disease

 Management

 Treatment of acanthosis nigricans  generally focuses on addressing the underlying conditions  causing it, specifically risk factors and diseases causing insulin resistance are addressed.If obesity is the major cause weight reduction may help to reduce the dark patches of acanthosis nigricans [5].

Insulin resistance associated with diabetes, poly cystic ovarian syndrome and metabolic syndrome  is managed with medications, exercise programs, stress reduction techniques ,life style and dietary modifications.

Acanthosis nigricans associated with insulin resistance may be treated with drugs such as metformin and rosiglitazone which are insulin-sensitizing agents by conventional medicine doctors [6]. The exact pathogenesis still unknown.

Acanthosis nigricans associated with malignancy may resolve if the causative tumor is removed successfully.

References          

1.       https://pubmed.ncbi.nlm.nih.gov/29184811/

2.       https://pubmed.ncbi.nlm.nih.gov/29209995/ 

3.       https://pubmed.ncbi.nlm.nih.gov/27921251/

4.       https://www.ncbi.nlm.nih.gov/books/NBK431057/

5.       https://pubmed.ncbi.nlm.nih.gov/15186199/

6.       https://pubmed.ncbi.nlm.nih.gov/18492785/

7.        https://pubmed.ncbi.nlm.nih.gov/29706998/