Teaching Case

A 68-year-old woman with no personal or family history of breast cancer consulted for a painful indurated mass in the left breast, accompanied by erythema of the overlying skin on the upper outer quadrant of the breast. No fever or history of trauma was noted. During the physical examination, similar smaller lesions were identified affecting the left forearm and both thighs.

Initial bilateral mammography (Figure 1) revealed a focal asymmetry in the upper outer quadrant of the left breast, accompanied by pre-glandular fatty tissue reticulation and localised skin thickening. There was no associated nipple retraction. No suspicious mammographic signs were found in the right breast.

Subsequently, a breast ultrasound (Figure 2) was conducted, demonstrating a non-vascularized area of fat-tissue hyperechogenicity affecting the upper outer quadrant of the left breast, corresponding to the palpable lesion reported by the patient and underlying an area of skin erythema. Focal skin thickening could also be identified. No axillary lymphadenopathies were noted.

A targeted ultrasound study of the extramammary lesions (Figure 3) revealed findings that overlapped with the breast study.

The 3-month follow-up breast ultrasound (Figure 4) demonstrated an improvement of the findings, with a residual subcutaneous band-patterned hyperechoic area containing millimetric oil cysts in the affected area.

Background

A punch biopsy of the breast skin was performed. The histopathologic examination revealed a lobular granulomatous panniculitis, consistent with Erythema Induratum of Bazin. The Interferon-Gamma Release Assay test came back positive, indicating tuberculous infection (not distinguishing active from latent).

Erythema Induratum of Bazin, also known as nodular vasculitis, is a specific form of granulomatous panniculitis associated with tuberculosis exposure (latent or active), which entails a hypersensitivity reaction with features of both type III (immune-complex-mediated) and type IV (delayed-type) hypersensitivity reactions.

As any other form of panniculitis, it causes an inflammation of the subcutaneous fat that manifests as violaceous subcutaneous nodules with tendency to ulcerate, typically affecting the lower extremities, being the breast involvement very rare [1].

Clinical Perspective

Fat necrosis is one of the most common benign lesions affecting the breast tissue. It is an inflammatory process that occurs secondarily to saponification of local fat and, due to its connection with surgical procedures, it is becoming more prevalent nowadays.

Despite its association with traumatic causes (both iatrogenic or non-iatrogenic), it has also been related to other clinical conditions, including local pathologies, such as plasma cell mastitis, and systemic diseases, predominantly linked to various forms of panniculitis. Therefore, before assuming a local traumatic source, a broader differential diagnosis should be considered.

Imaging Perspective

On mammographic studies, these lesions manifest with variable appearances depending on the temporal evolution, including focal asymmetries or even spiculated masses that mimic malignant entities [2].

Ultrasonography typically reveals a non-specific hyperechogenicity of the affected subcutaneous fat, corresponding to the acute phase of fat necrosis. This finding may progress to cystic and subsequently calcified lesions (oil cysts), even after successful treatment [3].

As imaging findings are non-specific, the certain diagnosis relies on the combination of visual characteristics of the lesions, evidence of systemic latent or active tuberculous infection and histopathological findings.

Thus, the diagnostic process always requires an appropriate evaluation of patients’ medical history, as the presence of systemic involvement and the multiplicity of the lesions may alter the initial diagnostic approach.

Outcome

Although Erythema Induratum is not a life-threatening disease, early diagnosis of this condition remains crucial, as it could be the first manifestation of a disseminated active tuberculous disease, which implies a significant morbimortality. This cutaneous manifestation tends to show a favourable response to multi-drug anti-tuberculosis therapy.

In the present case, systemic involvement was excluded, and symptomatic treatment led to a favourable evolution of the lesions.

Learning Points

1. Despite its predominantly primary and post-traumatic aetiology, breast fat necrosis may also be developed as a manifestation of systemic diseases.
2. The multiplicity of the lesions and the clinical history can lead the diagnostic process of breast-involving systemic pathologies.
3. Tuberculous granulomatous panniculitis (Erythema Induratum of Bazin) is a rare cause of breast fat necrosis.

All patient data have been completely anonymised throughout the entire manuscript and related files.