What is hyperkeratosis of the nipple?
Hyperkeratosis of the nipple and areola is a warty pigmented thickening of the nipples and areolae [1–4]. It can be primary (idiopathic) or secondary to another disorder (see differential diagnosis).
Hyperkeratosis of the nipple and areola is also called naevoid hyperkeratosis and hyperkeratosis areolae mammae naeviformis.
Hyperkeratosis of the nipple and areola
Who gets hyperkeratosis of the nipple?
Primary hyperkeratosis of the nipple typically presents in adolescent females, with the rate in males being much lower [1,2,3]. No ethnic or geographical links have been reported.
What causes hyperkeratosis of the nipple?
The exact cause of hyperkeratosis of the nipple is not known. Although no hormonal alterations have been found, an endocrinological cause has been proposed due to its association with the female sex, oestrogen therapy, and pregnancy .
What are the clinical features of hyperkeratosis of the nipple?
The clinical features associated with hyperkeratosis of the nipple follow.
- The hyperkeratosis is located on the nipple and areola (although the entire breast can be affected) [1,4]
- It is usually bilateral [1,2]
- It presents as verrucous hyperpigmented plaques [1,3]
- The plaques are generally asymptomatic; and occasionally itchy [1,5].
What are the complications of hyperkeratosis of the nipple?
Hyperkeratosis of the nipple may cause embarrassment and cosmetic concerns . There are reported cases of difficulty breast-feeding from the affected breast .
How is hyperkeratosis of the nipple diagnosed?
Diagnosis of hyperkeratosis of the nipple relies upon the clinical presentation of the hyperkeratotic plaque(s) and findings on skin biopsy if the presentation is atypical.
Histopathological characteristics of hyperkeratosis of the nipple are:
- Othokeratotic hyperkeratosis
- Keratotic plugging
- A mild perivascular lymphocytic infiltrate in the dermis [1,3].
What is the differential diagnosis for hyperkeratosis of the nipple?
Secondary hyperkeratosis of the nipple [1,2,4] is usually unilateral. Examples include:
- Seborrhoeic keratosis — presents as one or more discrete, well-circumscribed lesions
- Papillomatous melanocytic naevus (mole) — onset is in childhood
- Epidermal naevus — a congenital linear warty plaque
- Leiomyoma of the nipple and areola (genital type) — a rare benign neoplasm; a painful solitary nodule 
- Acanthosis nigricans — typically affects skin folds but may involve nipple and areola
- Nipple papillomatosis — in which papules arise from the lactiferous duct
- Jogger’s or cyclist’s nipple — associated with a history of chronic rubbing
- Mammary Paget disease of the skin — unilateral and clinically/histologically distinct
- Malignant skin lesion, such as basal cell carcinoma, squamous cell carcinoma, or melanoma
- Cutaneous T-cell lymphoma (mycosis fungoides) — rare cases confined to the nipple have been described.
Unilateral hyperkeratosis of the nipple associated with pain, bleeding, ulceration, discharge, or nipple retraction should be investigated for breast cancer with breast examination, mammogram, and biopsy.
Bilateral secondary hyperkeratosis of the nipple and areola may occur with:
- Atopic dermatitis
- Darier disease
- Targeted cancer therapies (such as vemurafenib).
What is the treatment for hyperkeratosis of the nipple?
Untreated hyperkeratosis of the nipple does not usually interfere with the normal breast function. However, treatment of the lesion is sometimes requested for cosmetic reasons [3,4].
Cryotherapy is a suitable first-line treatment for hyperkeratosis of the nipple often with a cosmetically satisfactory result [3,4]. It may need to be repeated. Hypopigmentation is the main long-term risk of cryotherapy.
What is the outcome for hyperkeratosis of the nipple?
Without treatment, hyperkeratosis of the nipple persists.