Paget's disease of nipple with dermal invasion: A case report

Abstract Background Invasive mammary Paget's disease (MPD) is an extremely rare eczematous eruption on the nipple and areola with an invasion of the dermis by Paget cells. This entity can often be misdiagnosed and overtreated for invasive carcinoma of the breast. Case A 34‐year woman presented with a 2‐year history of right nipple eczema and right axillary lump for a month. Breast ultrasound revealed dilated intra‐nipple lactiferous duct and an enlarged right axillary lymph node. Histopathology from biopsy revealed MPD with ductal carcinoma in situ (DCIS) whereas final histopathology after right modified radical mastectomy revealed Invasive MPD with DCIS and axillary metastasis. She underwent adjuvant chemotherapy and is under hormonal therapy with complete remission for 18 months. Conclusion Awareness of invasive MPD is important to avoid misdiagnosis and probable radical treatment. Close follow‐up is warranted due to limited knowledge regarding treatment and prognosis of invasive MPD.


| INTRODUCTION
Paget's disease of the breast also known as mammary Paget's disease (MPD) accounts for about 1%-3% of primary breast cancer. 1 An underlying invasive carcinoma or ductal carcinoma in situ (DCIS) is present in most of the MPD. 2 MPD with nipple skin involvement and extending from lactiferous duct without basement membrane invasion is considered to be DCIS whereas invasion of tumor cells into the dermis by breaching basement membrane is considered invasive MPD. 2 Invasive MPD is an extremely rare condition with only around 35 patients reported until date. [3][4][5][6] In addition, only six cases of invasive MPD with axillary node metastasis have been reported. 3,4 Here, we report a case of a 34-year female who presented with nipple eczema and a right axillary lump for a month. Histopathology of the excised breast showed invasive MPD with lymph node metastasis.

| CASE REPORT
A 34-year female, P 3 L 2 D 1 , last childbirth 2 years back, presented with the complaint of right nipple eczema for 2 years and right axillary lump for 1 month. Initially, she noticed skin peeling off her right nipple associated with a pricking sensation. The lesion gradually increased involving the whole nipple associated with darkening of skin and irritation. There was no history of discharge, bleeding, or pruritus from the right nipple and it was unrelieved by any topical medications. She had no history of breast trauma. In addition, she noticed a lump in her right axilla for one month, gradually increasing in size and without any overlying skin changes. She had menarche at the age of 13 years with a regular cycle of 28-30 days.
She breastfed all her children for 2 years. There was no history of use of any hormonal contraceptives and she underwent tubal ligation during her last childbirth. Moreover, there is no family history of breast, ovarian, and prostate cancer. On examination, she had an eczematous lesion confined to the right nipple associated with darkening of skin without visible discharge. In the right axilla, a single, mobile, hard, non-tender mass of about 1 cm was present. Left breast and left axillary examination were normal. Examination of other systems was unremarkable and all the laboratory investigations were within normal range.
Ultrasound of the right breast and axilla showed dilated intranipple lactiferous duct showing sludge and an enlarged right axillary lymph node (30 mm Â 12 mm) with loss of fatty hilum. The left breast had a normal scan with normal axilla. Due to inconclusive findings, a full-thickness wedge biopsy from the right nipple and excision biopsy of a right axillary lymph node was done. A diagnosis of Paget's disease of the right breast with lymph node involvement was established.
The patient was 34 years old, so an MRI breast was planned. Due to financial reasons, she refused MRI breast. Following this, a contrast-enhanced CT chest and abdomen was done which did not reveal any lesion in the left breast. No distant metastasis was found.  (microinvasion) or T1a. 10 Since the treatment and prognosis of these two entities are different, each case should be carefully evaluated and staged accordingly. 11 Our patient had underlying DCIS and nodal positivity, however, was negative for any other organ metastasis.
Histopathologically, invasive MPD and skin involvement of breast cancer with pagetoid spread can have similar findings. 3 Dermal invasion is an important histopathological criterion for the diagnosis of invasive MPD like extramammary Paget's disease. 7 Pathologically, isolated or clustered Paget cells that have invaded the dermal-epidermal junction is the characteristic feature of MPD with dermal invasion. 12,13 If the depth of invasion is <1 mm from the dermal-epidermal junction or basement membrane, invasive MPD is again known as minimally invasive MPD. 14 However, a distinction should always be made between secondary Paget's disease and Paget's disease with

ETHICS STATEMENT
Not applicable.

CONSENT FOR PUBLICATION
Written informed consent was obtained from the patient before the submission of the report. The signed Institutional Consent Form is on file.

DATA AVAILABILITY STATEMENT
Data sharing is not applicable to this article as no new data were created or analyzed in this study.