Synchronous bilateral infiltrating syringomatous adenoma of the breast

Introduction

Infiltrating syringomatous breast adenoma is a rare, benign, infiltrating neoplasm of eccrine origin located in the dermis of the areola and nipple. ¹ It is composed of angulated glandular structures with variable amounts of epidermoid differentiation, which proliferate in a background of dense collagenous stroma. After initial description, more than 30 cases of syringomatous breast adenoma have been reported in the literature. ² In the literature, only one case of bilateral infiltrating syringomatous breast adenoma with asynchronous clinical presentation was described. ³ This is the first case report to describe bilateral, synchronous presentation of this rare breast adenomatous lesion which may mimic carcinoma clinically and radiographically.

Case presentation

Clinical features

Mammographic examination showed microcalcifications in both nipples and retromammilary regions (Figures 1a–b). Ultrasound revealed microcalcifications in both nipples and retromammilary regions, and bilateral heterogeneous zones with dorsal attenuation in retromammilary area (Figures 1c–d). Axillary ultrasound showed no abnormalities. Ultrasound-guided fine-needle aspiration of both lesions was performed. Cytological analysis showed aggregates of atypical epithelial cells and microcalcificates which were consistent with carcinoma.

OPEN IN VIEWER

Figure 1

(a–b) Mammographic examination showed microcalcifications in both nipples and retromammilary regions. (c–d) Ultrasound revealed microcalcifications in both nipples and retromammilary regions and bilateral heterogeneous zones with dorsal attenuation in retromammilary area. (e–h) Histological examination showed angulated glands and solid cords, lined by an inner layer of epithelial cells and by an outer layer of myoepithelial cells, immersed in desmoplastic stroma. (e) Haematoxylin/eosin ×40, (f) E-cadherin (×200), (g) p63 (×200) and (h) CK5/6 (×200)

Discussion

Infiltrating syringomatous adenoma is defined as locally recurrent and locally invasive tumour of the nipple/areolar region of the breast showing sweat duct differentiation. It is composed of infiltrating glandular structures and solid cords of cells with overt squamous differentiation.^1–3 To the best of our knowledge the presented case is the second reported case of bilateral occurrence of this adenomatous lesion, but the first report of synchronous bilateral presentation and patohistological confirmation. In the case reported by Coulthard et al. ³ syringomatous adenoma of the left breast was found six months after excision of the same type of lesion in the right breast. Both lesions were initially reported as tubular carcinomas with foci of squamous differentiation. Interestingly, 20 months after the left breast surgery, a third lesion adherent to the overlying skin was noted in the region of the left axilla. Histological analysis of this lesion showed characteristics typical for benign syringoma, and histological sections of previously excised breast lesions were reviewed with subsequent revisions of initial patohistological diagnoses. ³ Infiltrating syringomatous adenoma of the nipple is often misdiagnosed because clinical presentation, mammographic and ultrasound findings may mimic carcinoma. ³ Some patients had undergone mastectomy and axillary dissection because the lesion was misdiagnosed as a tubular carcinoma or an adenosquamos carcinoma.^3,4 However, tubular carcinoma rarely involves the nipple. Histologically, tumour cells of tubular carcinoma often exhibit apical cytoplasmatic snouts and are often associated with micropapillary or crybriform types of low-grade ductal carcinoma in situ and/or flat epithelial atypia. The basement membrane and myoepithelial cells around neoplastic tubules are absent, which can be confirmed by immunohistochemical stain for p63 and/or smooth muscle myosin heavy chain, in difficult cases. The presence of squamous differentiation is another distinctive feature not observed in tubular carcinomas. ² The differential diagnosis from low-grade adenosquamous carcinoma is not so clearly defined. Low-grade adenosquamous carcinoma is a welldifferentiated tumour with both glandular and squamous differentiation. Although the histological appearance is similar to infiltrative syringomatous adenoma, more peripheral localization in the breast parenchyma and ability to metastasize are two features that characterize low-grade adenosquamous carcinoma. In contrast, infiltrating syringomatous adenoma of the nipple is benign, but locally expansive lesion, with the ability to infiltrate smooth muscle and nerve but not to metastasize. ⁵ It has a tendency for local recurrence as a result of an incomplete excision. ⁵ However, a single case of infiltrating syringomatous adenoma with micrometastasis to a sentinel lymph node was reported. ⁶ Due to localization in differential diagnostic consideration, nipple adenoma should also be included. The main difference is that nipple adenoma often occurs with the necrosis or erosion of the epidermis, and usually exhibits florid ductal hyperplasia, with or without a mild degree of cytological atypia.

Conclusion

Infiltrating syringomatous adenoma is a rare lesion and deserves special attention to avoid misdiagnosis as a malignant process with subsequent unnecessary treatment. Because of simultaneous bilateral occurrence of this entity presented in this report, we believe that finding of infiltrating syringomatous adenoma in one breast should prompt careful examination of the opposite breast with adequate follow-up.