Accessory Breast Tissue (Mamma Aberrata) as a Rare Differential Diagnosis of Soft Tissue Swelling in the Axilla

Introduction

Axillary swelling is a common problem in pediatric practice and radiology. It is usually caused by lymph node swelling on the basis of lymphadenitis or lymphoma. In rare cases, it is caused by soft tissue tumors (rhabdomyosarcoma, lipoma, fibroma), vascular lesions (angiodysplasia, aneurysms), or an inflammation of sweat glands ([Table 1]).

Table 1 Most common causes of axillary swelling (Ey K et al. J Ultrasound Med 2009; 28: 923 – 939; Laor T et al. AJR 2004; 183: 1779 – 1781).
Tab. 1 Häufigste Ursache einer axillären Schwellung (Ey K et al. J Ultrasound Med 2009; 28: 923 – 939; Laor T et al. AJR 2004; 183: 1779 – 1781).

differential diagnoses of axillary soft tissue swelling in children
lymphadenitis (also caused by atypical mycobacteria)
lymphoma
abscesses of the perspiratory glands
soft tissue tumors (rhabdomyosarcoma, lipoma, schwannoma etc.)
vascular processes (aneurysms, malformations – arteriovenous fistulae etc.)
accessory breast tissue

However, axillary soft tissue swelling may similarly be caused by accessory breast tissue. It should thus be thought of as a possible differential diagnosis, especially in female adolescents and young women.

Here we describe such a case and present the corresponding characteristic imaging findings.