Background

Accessory breast carcinoma (ABC) occurs anywhere along the milk line, with the axilla being the most commonly involved site, followed by the inframammary area [1]. The incidence of ABC is around 0.2–0.6% and that of male ABC is more insidious [2]. Also, sweat gland carcinoma (SGC) is a rare low-grade malignant skin adnexal tumor [3, 4]. Clinically, it mostly occurs in the head and neck skin, followed by the axillary, chest wall, scrotum, and perianal areas with asymptomatic nodular growth. The clinical prognosis for SGC is poor, as it is prone to local recurrence and distant metastasis [5]. Previous studies have demonstrated that the incidence rate of SGC is about 0.05%, which accounts for about 2.2~8.4% of skin malignant tumors. The age of onset is 40–60 years old, and women are more common than men [6, 7]. Moreover, extramammary Paget’s disease (EMPD) is a rare kind of intraepidermal adenocarcinoma involving Paget cells. It is most common in areas with a lot of sweat glands and eccrine glands, like the vulva, genitalia, and perianal region, with a few cases in the armpit as well [8]. Sweat gland carcinoma with EMPD in the axilla is rarer.

A case of male ABC and a case of male SGC associated with EMPD were described in this article. The clinical features and the treatment process of these two patients were very similar. They both started with axillary mass and then underwent local mass resection in a hospital near their home. In the absence of imaging evidence, the final diagnosis mainly depended on the pathology, for example, the shape and size of cancer cells and immunohistochemical characteristics. We hope that by presenting these two cases, we can bring these rare diseases to the attention of medical practitioners and provide some evidence for their diagnosis.

Case presentation

Case 1

An 83-year-old man, a current smoker (180 packs per year) with a history of hypertension and coronary heart disease for more than 10 years, found a mass in his right axilla 1 year ago without redness, swelling, and ache. Until the tumor gradually increased to about 3 cm in size, the patient went to the nearest hospital and underwent local tumor resection on October 26, 2020. Then, he came to our hospital for further treatment. Imaging examinations such as CT, MRI, and PET/CT showed no abnormal enhancement or mass in the breast, no enlarged lymph nodes in the right armpit, and no distant metastasis (Fig. 1). A 3-cm-diameter nodule with skin was found on postoperative pathology. Histologically, poorly differentiated adenocarcinoma was found in subcutaneous fibrous tissue. Positive immunohistochemical staining for anti-gross cystic disease fluid protein-15 (GCDFP-15), GATA-3, cytokeratin (CK), CK7, and EMA and negative for estrogen receptor (ER), progesterone receptor (PR), prostate-specific antigen (PSA), CK20, CDX2, p504S, p63, P40, TTF-1, NapsinA, PLAP, Syn, and CgA. The expression of HER2 was 2+ by immunohistochemistry, and fluorescence in situ hybridization (FISH) showed no amplification, and Ki67 was 20% positive (Fig. 2). After combining the imaging examination, clinical physical examination, and immunohistochemical index, the patient was finally diagnosed with accessory breast cancer.

Fig. 1
figure 1

Imaging examination findings of a patient with accessory breast cancer. A Breast MRI showed no abnormal mass. B CT showed no enlarged lymph nodes in the right armpit

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Fig. 2
figure 2

Immunohistochemical staining results of a patient with accessory breast cancer. A Photo­micrograph showed poorly differentiated adenocarcinoma (hematoxilin-eosin stain × 20). B GCDFP-15 was positive. C GATA-3 was positive. D CK7 was positive. E CK20 was negative. F FISH showed no HER2 amplification

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A daughter of the patient had a history of breast cancer. The doctor advised the patient to complete the BRCA test, but the patient refused. In the evaluation of cardiopulmonary function, no further lymphadenectomy or chemotherapy was performed because the patient was too old and had coronary heart disease and serious arrhythmia. Finally, the patient was treated with intensity-modulated radiation therapy (IMRT) with 6MV X-ray between November 30, 2020, and January 11, 2021. The right operation area, the right axillary lymph node drainage area, and the right accessory breast area were all included in the radiotherapy area. The planning target volume (PTV) dose was 50 Gy/25 F/5 W, and the postoperative gross tumor volume (PGTVtb) dose was 60 Gy/30 F. From surgery to February 2022, the patient’s disease-free survival (DFS) has been more than 15 months.

Case 2

A 66-year-old male patient was referred to the nearest clinic for further treatment because he accidentally found a 1.5-cm mass in the left armpit, bulging and red in appearance, without pain and ulceration. On June 20, 2020, after a routine examination, left axillary tumor resection was performed in a nearby hospital. When he came to our hospital, our imaging examinations demonstrated that there was no clear mass in bilateral mammary glands, no obvious enlarged lymph nodes in bilateral armpits, and no metastasis of other organs (Fig. 3). The adenocarcinoma cell, which tends to be sweat gland origin, co-existed with Paget’s cells histologically as the principal component of this malignant tumor. Strong positive immunostaining of GCDFP-15, GATA-3, CK, E-cadherin, and P120-tcn and partial positive immunostaining of CK5/6, CK20, and P53 were observed in sweat gland carcinoma and Paget’s cells, whereas ER, PR, P53, Calponin, MelanA, S-100, HMB-45, and MUC2 did not stain. The expression of HER2 was 2+ by immunohistochemistry, and fluorescence in situ hybridization (FISH) showed amplification, and Ki67 was 20% positive. In addition, androgen receptor (AR) was 40% positive (Fig. 4). The patient was assessed for evidence of sweat gland cancer associated with extramammary Paget’s disease based on these findings.

Fig. 3
figure 3

Imaging examination findings of a patient with sweat gland cancer. A Breast MRI showed no abnormal mass. B CT showed no enlarged lymph nodes in the left armpit

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Fig. 4
figure 4

Immunohistochemical staining results of a patient with sweat gland cancer. A Histologically showed adenocarcinoma cells coexisting with Paget cells (hematoxilin-eosin stain × 20). B GCDFP-15 was positive. C GATA-3 was positive. D CK20 was partial positive. E AR was positive. F FISH showed HER2 amplification

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The patient was previously healthy and had no other complications, and his mother had a history of breast cancer. Thirty days after local resection, the patient underwent extended resection of the left axillary tumor and left axillary lymph node dissection. The pathology after operation displayed a small number of atypical cells under the mucosa of the left axillary tumor resection tissue, and no metastasis was found in the axillary lymph nodes (0/14). From September 4, 2020, to November 13, 2020, four cycles of TC (docetaxel and cyclophosphamide) regimen were used as adjuvant chemotherapy. The patients have been followed up on in good health so far, with no signs of recurrence or metastasis. The DFS was more than 19 months long until February 2022.

Discussion and conclusions

To our knowledge, ABC in males is extremely rare, and only a few cases are reported at present [9,10,11,12,35]. The treatment of EMPD depends on adequate surgical excision that should be sufficiently wide in surface and depth to eradicate the entire tumor mass. Although the margin of 1 cm is enough, 2 cm is often recommended as a safe margin because the margin of this type of disease is not very clear [36]. The negative margin on frozen sections and Mohs graphic surgery ensures a low recurrence rate [37]. Combined with the characteristics of the above two diseases, our patient finally underwent extended resection and lymphadenectomy. Besides, we also gave the patient systemic chemotherapy (docetaxel and cyclophosphamide) after surgery. We suggested that he receive anti-HER2 targeted therapy, such as trastuzumab, because of his HER2 gene amplification, but the patient ultimately declined due to financial concerns.

In general, the incidence of these two diseases reported by us is very low, especially when both of our cases are male. Although both patients developed an axillary lymph node mass at the same time, their final diagnoses were different. As the two patients had tumor resection in other hospitals, the information about the initial tumor is lacking, and the later diagnosis mainly depends on pathology.