Idiopathic granulomatous mastitis

Thirty-three years old female with acute mastitis on the right breast started two months ago, treated with oral antibiotics. After treatment, she responds partially to skin inflammation and shows a palpable mass, induration, pain, and skin ulceration.

Axial T2 and STIR images showed a slight skin retraction and ulceration on upper union quadrants of the right breast, peri-lesional parenchymal oedema, and an irregular hiperssinal on T2 mass. (Fig. 1a,1b).

Because of the clinical symptoms of breast pain, induration, and skin ulceration in a young patient, mammography was postponed. The MRI and biopsy were performed on the same day.

The dynamic study Axial T1 fat-sat first-minute post-contrast and sagittal MPR reconstruction demonstrate high heterogeneous enhancement of the mass and the skin. (Fig. 2a,2b)

MIP of the first minute shows a spiculated mass and vascular ectasia of the left breast. (Fig. 3)

Multiparametric map MSI (maximum slope increase) shows coloured in red the highest contrast enhancement areas (Fig. 4a)

The kinetic evaluation presents ascendant curve type I. (Fig. 4b)

Diffusion imaging shows restricted Diffusion (ADC=0.855 × 10−3 mm2/s). (Fig. 5)

Ultrasound confirms the presence of a solid irregular mass with small cysts collections, perilesional fat oedema, and peripheric vascularization on power doppler images. (Fig. 6a, 6b)

Background

Granulomatous mastitis is a rare inflammatory disease known as nonpuerperal mastitis or granulomatous lobular mastitis. [2]

The pathogenesis and aetiology are unknown, although it was observed that it usually affects young parous premenopausal women and is clinically associated with hyperprolactinemia [including drug-induced]. Has been suggested by some authors an infective or immune aetiology.[4][5][6]

Clinical Perspective

Granulomatous mastitis usually manifests as a tender palpable mass, breast induration and inflammation, skin erythema, oedema, and ulcerations; it also may manifest with isolated abscess with or without draining skin sinus. The disease may be bilateral, and the nipple is seldom involved. Reactive lymphadenopathy may be present. [2] [3] [4]

Imaging Perspective

A core biopsy was performed to exclude breast carcinoma. The histopathological analyses revealed a chronic noncaseating granulomatous inflammation, giant cells, leukocytes, macrophages, and abscesses without infection. 

Mammographic features are nonspecific and variable from new asymmetric densities, focal asymmetries, ill-defined masses, or negative mammograms in dense breasts. [1][4].

The ultrasound presented a unique large mass with small collections and subcutaneous fat obliteration, skin thickening, and fistula. Although the features can vary, our case didn't show others' findings, such as focal regions of inhomogeneous patterns associated with contiguous hypoechoic tubular lesions or multiple and confluent lesions. [1] [4]

The MRI features are heterogeneously enhancing mass [or masses] or rim-enhancing lesions that could be associated with segmental or regional non-mass enhancement. The lesions can demonstrate irregular or well-defined borders, and most of the masses have a T2-hyperintense sign. [1][4]The enhancement kinetic is nonspecific; most of them are progressive or plateau curves. Diffusion images show restriction. [1]

Associated imaging findings include axillary adenopathy, nipple and skin thickening, sinus tracts, parenchymal distortion, and oedema. [1]

Outcome

The patient was treated with an oral anti-inflammatory drug and presented a complete clinical response after two months of treatment. Although the reported recurrence rates were up to 50%, our patient didn't show recurrence after seven months of follow-up. Others treatment options are surgical excision, steroid therapy, or methotrexate. [4]

Take-Home Message, Teaching Points

Granulomatous mastitis is a very rare inflammatory disease, but the diagnosis should be considered in young parous premenopausal women with refractory inflammatory mastitis symptoms. 

At imaging can present a variety of nonspecific appearances, which often mimic malignancy requiring biopsy to exclude breast carcinoma. The MRI can study the extension of the disease but does not accurately differentiate an inflammatory lesion from neoplasia.

Written informed patient consent for publication has been obtained.