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A 46‐year‐old woman with a rare case of infiltrating lobular carcinoma in ectopic breast tissue on the anterior chest wall is presented. Wide local excision and lymphatic mapping with, consequently, a sentinel node biopsy, seem adequate therapy for ectopic breast cancer.
Ectopic breast tissue arises from the primitive milk line, with an incidence of 0.6–6%.1 Malignant transformation is rare.2 The most frequently occurring manifestation is infiltrating ductal carcinoma, comprising 79% of all ectopic breast malignancies.3 Lobular‐type and medullary‐type carcinomas are seen in <10% of cases.4 Furthermore, most carcinomas in the ectopic breast tissue are located in the vulva and axilla (ie, 55–65%).5 The chest wall is the most unusual location.6
We present a patient with lobular carcinoma in ectopic breast tissue located on the anterior chest wall.
A 46‐year‐old Caucasian woman presented with a subcutaneous mass in a cicatrice of the anterior chest wall approximately 1–2 cm below the caudal rim of the mammary gland. At that location, she had undergone surgical excision of ectopic breast tissue without signs of malignancy, 22 years ago. She had noticed the present swelling 2 weeks previously, without further symptoms. She was premenopausal and had no family history of breast cancer.
Clinical examination and x rays of both breasts and axillae were found to be normal. Clinical examination of the scar on the anterior chest wall showed a firm subcutaneous mass of approximately 4 mm in diameter (fig 11).). Ultrasonography of the mass showed only scar tissue.
Excisional biopsy was performed, and pathology showed a pleomorphic lobular carcinoma of 1.2 cm in size with areas of ductal carcinoma in situ arising from ectopic breast parenchyma. The cells of the pleomorphic lobular carcinoma form a “single file” pattern (ie, aligned in a row) (fig 22).). Immunostaining for E‐cadherin was negative. The tumour was irradically excised, and showed a mitotic activity index of 13 per 2 mm2, Bloom Richardson grade III, negative Her‐2‐neu receptor status and positive oestrogen and progesterone receptors.
Thus, re‐excision of the accessory breast tissue tumour was performed after lymphatic mapping and sentinel node biopsy (fig 33).). One sentinel node was identified in the ipsilateral axilla.
Final pathology showed mammary gland tissue with remnants of the aforementioned lobular carcinoma, now with negative margins. Pathology of the sentinel node biopsy showed metastasis with extranodal growth. Therefore, an axillary lymph node dissection was performed. Final pathology showed no metastases in the second echelon axillary lymph nodes.
To exclude a primary breast cancer, MRI of the mammary glands and axillary regions was performed, showing no pathological features. The patient received adjuvant radiotherapy of the chest wall, chemotherapy (5‐fluorouracil, epirubicin and cyclophosphamide), followed by hormonal treatment.
In a review study on all published cases of ectopic breast cancer from 1865 to 1994, only three cases of ectopic breast cancer arising in the chest wall were found.6 Combining this with the fact that lobular carcinoma in ectopic breast cancer is seen in <10% of cases makes our patient with infiltrating lobular carcinoma in ectopic breast tissue on the anterior chest wall an exceedingly rare case.5
In a study on 90 cases of carcinoma in ectopic breast tissue, radical or modified mastectomy offered no advantage in outcome over wide local excision combined with regional node dissection.7 In our patient, local excision showed irradically excised infiltrating lobular carcinoma, therefore wide local re‐excision was performed with negative margins.
Lymph node status is an important prognostic factor in breast cancer.8 Some authors have even reported an increased incidence of metastasis to regional lymph nodes with earlier involvement in ectopic breast cancer compared with standard breast cancer.9,10 However, the anatomy of lymphatic drainage of the ectopic breast is unclear. The use of lymphatic mapping may show these lymphatic pathways. In a recent study, the sentinel node technique was successful in isolating an unusual group of lymph nodes. This allowed more accurate staging of the disease and more appropriate adjuvant treatment.11 In our patient, the sentinel node was located in the axilla and was positive for metastases. Completion axillary lymph node dissection was therefore performed.
In summary, we present a case of infiltrating lobular carcinoma in ectopic breast tissue on the anterior chest wall. As ectopic breast cancer is a rare entity and literature on the subject is sparse, drawing conclusions about the appropriate treatment is daunting. However, combining the data from our case with previous studies, wide local excision and lymphatic mapping with, consequently, a sentinel node biopsy seem adequate therapy for ectopic breast cancer.
Competing interests: None declared.