Nipple adenoma presenting as persistent erosive nipple in a young woman

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Nipple adenoma is a rare benign tumour caused by adenomatous proliferation of the lactiferous ducts. It presents as a unilateral erosion, with or without serosanguinous discharge. Diagnosis relies on histopathological examination, which is characterised by proliferation of tubules lined by both epithelial and myoepithelial cells.¹ Due to its rarity, nipple adenoma is frequently misdiagnosed, making accurate histopathological diagnosis critical for effective management.

A 26-year-old female presented with persistent erosion of the left nipple with occasional serosanguinous discharge for 2 years. She was previously diagnosed with nipple eczema and treated with topical and oral antibiotics and topical steroids without any improvement. Examination revealed an irregular erythematous erosion of size 0.5 x 0.5 cm involving the centre of the left nipple [Figure 1]. There was no palpable mass, active discharge, bleeding, or regional lymphadenopathy. The right breast was unremarkable, and there was no family history of breast cancer. Based on these findings, differential diagnoses of erosive adenomatosis, Paget’s disease of the nipple, and nipple eczema were considered.

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Figure 1:

Irregular superficial erosion involving the centre of the left nipple.

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Ultrasound of the breast showed a well-demarcated hypoechoic uniformly solid nodule in the left nipple [Figure 2]. Contrast-enhanced magnetic resonance imaging (MRI) of the left breast revealed thickening and enhancement of the nipple, showing washout and mild adjoining cutaneous thickening with no retro-areolar mass. An incisional biopsy from the edge of the lesion revealed an unencapsulated tumour comprising adenomatous and cystic structures with ductal proliferation, separated by scant stroma in the dermis [Figures 3a and 3b]. The cystic spaces had an inner lining of columnar epithelium with decapitation secretion, showing occasional intraluminal papillomatosis and a flattened to cuboidal outer layer of myoepithelial cells [Figure 3c]. Immunohistochemical staining showed ductal cells positive for cytokeratin 7 [Figure 3d], while surrounding myoepithelial cells stained positive for calponin [Figure 3e] and p63. Based on the clinico-pathological and radiological findings, a diagnosis of nipple adenoma was made. The nipple was completely excised with reconstruction, and no relapse was noted after one year of follow-up [Figure 4].

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Figure 2:

Ultrasound of breast showing a well-demarcated hypoechoic uniformly solid nodule in the left nipple.

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Figure 3a:

Unremarkable epidermis with dermis showing unencapsulated tumour (Haematoxylin and eosin, 100x).

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Figure 3b:

Tumour comprising of cells arranged in glands or ducts with back to back arrangement and scant intervening stroma (Haematoxylin and eosin, 200x).

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Figure 3c:

Bilayered ductal epithelium with focal epithelial hyperplasia and short papillary projections (Haematoxylin and eosin, 400x).

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Figure 3d:

Luminal ductal epithelial cells were positive for CK7 (CK7 immunohistochemistry, 100x).

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Figure 3e:

The outer layer of myoepithelial cells was positive for calponin stain (Calponin immunohistochemistry, 100x).

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Figure 4:

Clinical image after complete excision followed by reconstruction of the left nipple.

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Nipple adenoma, also called florid papillomatosis of nipple or erosive adenomatosis, is a rare benign tumour resulting from adenomatous proliferation of the lactiferous ducts, accounting for 0.1- 1.7% of benign breast lesions.¹ It mainly affects middle-aged women; however, rare cases have been documented in men and children.² It is characterised by asymptomatic unilateral nipple erosion with serosanguinous discharge. Nipple ulceration, distortion, induration, or tumour formation may occasionally be observed.² Clinically it must be differentiated from Paget’s disease of the nipple, nipple eczema, and lactiferous ductal ectasia.³ Paget’s disease of the nipple typically occurs in postmenopausal women as an oozy erythematous plaque on the breast with bloody discharge and destruction of the nipple-areolar complex. It is typically associated with an underlying breast carcinoma. Characteristic histological findings include large, pale-staining Paget cells within the superficial epidermis. Nipple eczema, by contrast, is characterised by itchy red scaly plaques on one or both nipples. Skin biopsy shows spongiotic dermatitis with lymphocytic infiltration in the superficial dermis.³

Imaging techniques detect subtle changes that may help in evaluating tumour extent and excluding malignancy.¹ Sonographic findings in nipple adenoma may include a hypervascular, well-defined mass, demonstrating variable echogenicity, while mammogram frequently fails to identify these abnormalities.⁴ Histopathological examination reveals a well-circumscribed, non-encapsulated tumour exhibiting adenomatous hyperplasia without cellular atypia. The lining of the duct consists of an inner layer of epithelial cells with an apocrine secretion and an outer layer of myoepithelial cells. This dual cell layer is the main feature that distinguishes it from invasive or in situ carcinoma.² The histologic subtypes described are i) sclerosing papillomatosis pattern; ii) papillomatosis pattern with florid papillary hyperplasia of ductal epithelium; iii) adenosis pattern with myoepithelial hyperplasia; and iv) mixed proliferative pattern, a combination of three patterns.⁵ Immunohistochemical analysis of the inner epithelial layer reveals cytokeratin 7 positivity; conversely, outer myoepithelial cells exhibit positivity for α-smooth muscle actin, p63, calponin, and cytokeratin 5/6.⁶ Histopathological differentials for nipple adenoma include benign apocrine tumours, such as syringocystadenoma papilliferum, hidradenoma papilliferum, and tubular apocrine adenoma [Table 1].⁷

Complete surgical excision with clear margins followed by nipple reconstruction is the recommended treatment for nipple adenoma due to its locally infiltrative nature.² Nipple-sparing approaches such as wedge resection, enucleation, Mohs surgery, and cryosurgery may yield superior cosmetic outcomes. However, a 25-55% recurrence risk with incomplete excision has been reported.¹ Regular monitoring is suggested in view of instances of co-existence of nipple adenoma and breast cancer, and the possibility of recurrence.³

We describe a rare case of unilateral nipple erosion in a young female that warranted exclusion of several potential differential diagnoses. Accurate and timely diagnosis using histopathology is paramount for successful management in such a case.