Abstract:
I would like to present about 50-years-old female who presented erythema and erosion of her left nipple, then she came to our hospital for further examinations. Mammography and Ultrasonography suggested “not breast cancer but cutaneous lesion”.
A core needle biopsy specimen revealed “nipple adenoma (NA)”, and complete local excision was subsequently performed by surgeons.
On, histopathological view, surgical specimen demonstrated a circumscribed nodular lesion with no fibrous capsule border with which composed of a variety of tubular, papillary, and cribriform proliferations with a preserved biphasic epithelial and myoepithelial architecture (LE and ME) accompanied by thin fibrous proliferations in the nipple lesion. Necrosis and mitoses were rarely observed consistent with the previous studies. However, nipple discharge of the origin such as haemorrhage were easily observed by maintaining bilayer LE-ME structure. Based on these histopathological findings, a diagnosis of “nipple adenoma” was confirmed.
Haematoxylin and Eosin (H&E) staining revealed multiple “squamous cell cysts” adjacent to the superficial epidermis, accompanied by surface erosion. Morphologically, continuity between LE cell structure and the metaplastic squamous epithelium of mixed features was demonstrated in one lactiferous duct of some. Previous studies revealed “Syringomatous tumours” of epidermal extension mechanism may resembled almost of the “nipple adenoma” was suggested from previous studies and our case was consistent with “this hypothesised theory”. These theories might be possibly mediated by “LE replacement of squamous epithelium of main lactiferous duct” observations.
In other studies, indicated LE cells might open to the epidermis via continuity by “replacement mechanism”. However, it’s hypotheses are complicated because anatomical studies showed NA of LE cells should not necessarily open to “main lactiferous duct” by replacement style. Now, it might be suggested the theories integrated to LE cells showing “open to sebaceous gland and/or accessory lactiferous ducts (in the textbook, 15-20, however many multiple variations are known) and/or LE cells located the basement membrane of squamous epithelium is known to by anatomical knowledge.
In our case, immunohistochemical analyses demonstrated the coexistence of squamous components and glandular epithelial cells mixed in “one squamous cell cyst”. We have previously reported “the squamocolumnar junction (SCJ) in low-grade ductal carcinoma in situ involving the nipple”. Based on our experiences, we hypothesize that NA, whereby glandular epithelial cells undergo “complex epithelial remodelling” associated with squamous metaplasia, extending across to the SCJ, and contribute to disruption of the nipple epithelium, ultimately resulting in “nipple surface erosion” whereas maintaining bilayer structure, these continuous phenomenon might not be explained only “main lactiferous duct replacement theory”, we speculated.
Based on our presented studies, we aimed to clarify both histopathological and immunohistochemical findings. Together with a review of the reported literature, we propose this potential mechanism would not explained not only “main lactiferous duct replacement theory” but also “another pathway” might be allowed to one speculation theory from our SCJ hypothesis of “complexed pathway”.
