Diagnostic and Interventional Radiology in Idiopathic Granulomatous Mastitis

Idiopathic granulomatous mastitis is a chronic, benign, inflammatory disease of the breast. If the radiological findings are known, patients can be referred for biopsy in the early period. The diagnosis of the disease must be based on a histologic confirmation. After diagnostic and therapeutic management, a radiological follow-up is conducted using an appropriate imaging tool. In this study, we highlight the radiologic evaluations for idiopathic granulomatous mastitis and present specific cases.


Introduction
Idiopathic granulomatous mastitis is a chronic, inflammatory, benign disease of the breast.Benign and malignant breast diseases show similarity with regard to clinical and radiological outcomes [1].Therefore, it is essential to evaluate the imaging findings accurately and provide a fast, conclusive diagnostic path [2].A pathologic confirmation not only provides discrimination from malignancy, but also enables the provision of the most appropriate treatment regimen to the patient.

Interventional Procedures
The disease must be diagnosed through a pathological evaluation.Fine needle aspiration is principally supportive in detecting purulent secretions at the early stage.Nevertheless, it could not be satisfactory in distinguishing malignant and other benign inflammatory disorders.A core biopsy should be preferred for this purpose.Although larger tissues can be obtained, vacuum-assisted biopsies may result in fistula development.A diagnostic excisional biopsy is not preferred due to substantial scratching, loss of breast symmetry, breast deformity, and the possibility of unhealed ulcers or sinus tract formation [5,6].
For the diagnostic management of granulomatous mastitis, not only the tool but also method is of great importance.Particularly, as mentioned below, sampling of lesions with different radiological and pathological components, such as edema, inflammation, necrosis, and abscess, requires skill and expertise.Sample collection from the thick walls of the necrotic lesions or abscesses and specimens of inflamed areas having vascular signals will provide an adequate pathological result (Figure 1).With this aim, the radiology of idiopathic granulomatous mastitis is reviewed in the light of literature and exemplary cases.

Ultrasonography
Thickening of the skin, an irregular hypo-echogenic mass with tubular extensions, smoothedged hypo-echogenic mass, hypo-hyperechoic-heterogeneous mass, masses that tend to coalesce, heterogeneous parenchyma, parenchymal edema, distortion, acoustic shadowing, abscess, sinus tract formation or lymphadenopathy may be detected [9] (Figure 3).On a greyscale, granulomatous mastitis lesions are seen as very heterogeneous lesions with a wide range of brightness.Based on this idea, a study on the texture analysis of granulomatous mastitis and carcinoma lesions showed that texture analysis may be a proficient method in differentiating between granulomatous mastitis and breast carcinoma.It may offer measurable statistics about the lesions and an unbiased evaluation compared to a visual inspection [10].
Additionally, ultrasonography is the main followup tool after an appropriate treatment regimen.

Doppler Ultrasonography
Prominent arterial and venous Doppler signals can be found in the inflamed parenchyma [11].In addition, Doppler signals are also helpful for a biopsy guidance.During a classical biopsy procedure, it has to be avoided a biopsy trace falling into any vascular structure.In contrast, if granulomatous mastitis is suspected, biopsy specimens must be obtained from vascularized

Elastography
Compressive sonoelastography in idiopathic granulomatous mastitis shows soft properties with low elasticity scores and strain ratios [12] (Figures 4 and 5).These features can be attributable to the pathologic properties.Non-caseating granulomas concentrated in the lobules, an inflammatory environment, and lymphoplasmocytic migration may be observed.Microab-scesses, necrosis, sinus tracts, and duct ectasia are frequently observed [3,13].Using acoustic radiation force impulse imaging, idiopathic granulomatous mastitis has been reported to have low median marginal and internal velocities compared to malignant lesions [14].

Magnetic Resonance Imaging
Upon magnetic resonance imaging, skin alterations owing to inflammation; T1, T2, and STIR intensity changes; and intense contrast uptake, progressive, plateau or washout pattern; mass lesions with ring enhancement; segmental-re-gional non-mass enhancement; diffusion changes; necrosis-abscess; fistula tracts; skin abscess; dilated ducts with dense content; enhanced ductal walls, and lymphadenopathy can be perceived [5,15,16].Idiopathic granulomatous mastitis is often seen in premenopausal women presenting with signs of mastitis and a mass.Therefore, their initial evaluation is based on ultrasonography rather than mammography and magnetic resonance imaging.An appropriate antibiotic therapy and immediate follow-up are recommended at the first admission.Thereafter, the biopsy has to be performed when there is no clinical improvement.In this clinical setting, magnetic resonance imaging should be used for the evaluation of advanced-aggressive-unresponsive disease when the sensitivity of ultrasonography and mammography is limited due to parenchy- mal edema, biopsy guidance, a standard follow-up imaging tool especially in extensive involvement, evaluation of residual disease after treatment, and evaluation of the other breast [8,17,18] (Figures 6-8).
A recent study on T1 perfusion magnetic resonance imaging showed that the perfusion properties of benign inflammatory lesions, including pathologically proven idiopathic granulomatous mastitis, were similar to those of malignant lesions.K trans is the transfer constant from the plasma to interstitium, K ep is the reverse transfer constant, and V e is the extracellular matrix volume fraction.K trans and K ep values were higher and V e values are lower, similar to malignant lesions [19].
In diffusion-weighted imaging, inflammatory conditions can show diffusion alterations due to edema, inflammatory cell migration, high viscosity, and cellular debris [16,20].

Conclusion
With only imaging findings, idiopathic granulomatous mastitis cannot be easily distinguished from malignancy.Clinical and radiologic features can be confounding and cannot differentiate between particularly diffuse breast carcinomas or specific subtypes of breast carcinoma.Thus, an early pathologic confirmation is a must when antibiotics do not work (Figure 9).The response to treatment must be monitored using ultrasonography.Magnetic resonance imaging is a follow-up tool in aggressive, diffuse, and irresponsive disease.

Conflict of Interest:
The author has no conflict of interest to declare.
Financial Disclosure: The author declared that this study has received no financial support.
Mammography A mammogram may show thickening of the skin, focal or global asymmetry, irregular focal mass, trabecular coarseness or distortion in the parenchyma, smooth-edged mass, calcification, or lymphadenopathy

Figure 1 .Figure 2 Figure 3
Figure 1.a-d.Identification of idiopathic granulomatous mastitis should be established histologically.A tubular, hypo-echogenic, wellbordered lesion without acoustic shadowing is sampled using a core biopsy device (arrow) (a).Lesions having necrotic constituents should be evaluated carefully and necrotic portions (stars) should not be sampled (b).Thick walls (c) and vascularized areas (d) have to be chosen for a proper histologic result during the biopsy procedure

Figure 4 .Figure 5 .Figure 6 .
Figure 4. a-c.Compressive sonoelastography image (a) obtained by the dual mode of an idiopathic granulomatous mastitis lesion demonstrates its soft nature with a low elasticity score (2) and strain ratio (1.23).The Doppler image (b) shows low resistant arterial flow, and core biopsy (c) is performed for this vascular lesion

Figure 7 .Figure 8 .Figure 9
Figure 7. a-d.Multi-loculated, necrotic mass with peripheral and septal intense enhancement is seen in the subareolar region of the left breast (a).A diffusion-weighted image of the lesion shows prominent restriction (b).A coronal STIR image shows enlarged left axillary and oval lymph node (c).Upon compressive sonoelastography (d), the lesion appears very soft (elasticity score: 1, strain ratio: 0.54)