Imaging of tubercular mastitis presenting as recurrent breast nodules and abscesses: a rare case report

Tubercular mastitis could be a rare diagnostic find clinically. It is largely seen in Asian, African and alternative non-developed countries and might occur with coincident primary tuberculosis of the respiratory tract or spine. Primary breast tuberculosis (TB) is even rarer and presents with non-specific clinical signs of continual breast masses, inflammation and sinus tracts. It can be similar to bacterial inflammation/abscess and malignant pathologies on imaging. The key to identification could be a holistic combination of imaging, clinical, biochemical and histopathological analysis. We discuss a case of a 41-year-old lady who conferred at the start with tender breast nodules that progressed to continual, multiple abscesses and sinus tract formation. It had been an unusual and unanticipated presentation in breast followed by uncommon events throughout the course of the treatment forcing us to re-evaluate the primary diagnosis. A sequence of multiple diagnostic imaging and histopathological evaluations confirmed the identification of tubercular mastitis. Following prolonged treatment, there was vital reduction within the range and size of nodules and abscesses. Such cases imitate bacterial abscess and cancer in their clinical presentation and imaging findings and are imperative to be diagnosed via a myriad of diagnostic tests with histopathology. Such a clinical presentation should warrant a differential of granulomatous inflammation of the breast in cases of non-responders to incision and drainage, prolonged antibiotic medical therapy and prolonged anti-tubercular treatment up to twenty four months after assessment of the individual response.


Background
Tuberculosis is a communicable disease caused by Mycobacterium tuberculosis bacillus which might survive and duplicate within the macrophages of the host [1]. Though tuberculosis primarily attacks the lungs, different organs also are in danger of infection [2]. The primary case of breast TB was reported in 1829 by an outstanding English medical professional (surgeon) Sir Astley Cooper, who delineated it as a "scrofulous swelling of the bosom. " [3].
Here, we intend to report a case of a 41-year-old woman with repeated breast masses having atypical Breast Imaging Reporting and Data System (BIRADS) three lesions each on mammography and ultrasound that underwent resolution in terms of range and size. On anti-tubercular treatment (ATT), recurrent fine-needle aspiration cytology (FNAC) and diagnostic biopsy characterized them as benign tubercular mastitis. A case presenting with nodular-type lesions, resulting in multiple abscess formation with rupture into fistulous tract and skin involvement, has not been reported hitherto within the literature to the best of our knowledge.

Case presentation
A 41-year-old woman, multipara with no history of recent lactation, presented to the OPD with complaints of multiple tender nodules and pain in bilateral breasts since one week in the month of October in 2019. On clinical examination, a medical diagnosis of breast abscess was considered and she was started on a course of antibiotics and anti-inflammatory medication. No imaging was suggested then. After 4 months, there was decrease in pain, but the nodules persisted. A mammogram with ultrasound was performed for the patient in January 2020 which revealed multiple hyperdense masses in bilateral breasts with partly circumscribed and partly obscured margins (Figs. 1, 2). Ultrasonography showed corresponding well defined wider than taller heteroechoic regions with circumscribed margins showing internal mobile debris. A few of these lesions showed conglomeration. Multiple intra-mammary nodes were also noted scattered throughout bilateral breast parenchyma, few showing necrosis within (Figs. 3,4). Axillary necrotic and conglomerated lymph nodes were also noted bilaterally. A BIRADS score of 3 was given in bilateral breasts.
On subsequent FNAC of the mass lesion, cytological evidence of epithelioid cell granulomas, lympho-histiocytic aggregates and Langerhans's giant cells without caseous necrosis was found leading to the diagnosis of tubercular mastitis. The diagnosis of primary tubercular mastitis was confirmed on the basis of positive QuantiF-ERON TB assay. A screening evaluation of the lung, cervical lymph nodes and the spine was done to look for primary site of involvement, which were all negative. Anti-tubercular treatment was started for the patient (Category 2) with intensive therapy for 2 months followed by continuation therapy.
The patient showed worsening of symptoms on starting the treatment. There was increase in pain, formation of breast abscess which ruptured and presented as multiple discharging sinuses. Dressings were done, and patient was motivated to continue the oral medications alongside. Within a month, the patient showed improvement of symptoms with reduction in the size of the masses and absence of active discharge. She was continued on medication for 2 more months.
Her axillary nodes resolved followed by subsidence of pain in 4 months. By 8th month, there was reduction in the size and number of the breast nodules as well.
Serial ultrasound post one year of dedicated treatment in January 2021 showed marked reduction in the masses in bilateral breasts with resolution of axillary lymph nodes. However, skin thickening and few small residual masses remained in bilateral breasts.
Patient was continued on treatment with follow-up mammogram and ultrasound in January 2022. They showed marked reduction in the size of masses in the right breast with intra-mammary nodes remaining in the left breast (Fig. 5).
Patient is doing fine currently in March 2022. She has been advised to stop ATT and is advised to follow-up every 6 months.

Discussion
Breast TB accounts for fewer than 0.1% of all breast pathologies [4] and has been reported as 3-4.5% of breast pathologies requiring surgery in developing countries [5]. Multipara and women practicing lactation between the ages of twenty and forty are often affected. Breast TB can be either primary or secondary; however, primary breast TB is extraordinarily rare because the breast parenchyma is impervious against the tubercular bacillus [6]. The primary type of tubercular inflammation is caused by the extension of infection through abrasions within the skin of the breast or through cracks within the breast nipples. The secondary type is caused by the retrograde unfurling of the infection from infected axillary nodes, or by direct spread from tissue within the ball-and-socket joint of the shoulder, costo-chondral cartilage, ribs, sternum or pleural membranes adjacent to the ductal glandular breast tissue [6].
The clinical presentation is variable and ranges from a spectrum of multiple painless lesions that may be adhering to the skin or the chest wall, multiple discharging sinuses, skin inflammation and associated nipple retraction or skin thickening and axillary inflammation or nodal formation. This might cause diagnostic predicament because of similitude with cancer or bacterial breast infection.
In 1952, McKeown and Sir Geoffrey Wilkinson classified tuberculosis of the breast into 5 totally different types: nodular, mastitis obliterans, sclerosing, disseminated and acute military type of inflammation [7]. Caseous nodular type of inflammation is the commonest kind. It presents as a pain-free, oval, well-defined, slow growing, non-vascular hypoechoic mass, mimicking the looks of a fibroadenoma within the early stages of the disease. Later, it evolves to become a fistula within the nipple-areolar complex or on the skin and could closely remind of cancer [7].
On ultrasonographic examination, the nodular type of tubercular inflammation presents as lesion/lesions which take the shape of an indistinctly bordered, hypoechoic, heterogeneous mass which might mimic the looks of a slowly growing fibroadenoma and hence is classified as BIRADS three lesions [9]. Diffuse type of the mastitis shows multiple hypoechoic masses which are not well defined, while the sclerosing type shows exaggerated echogenicity of the breast parenchyma without a typical mass formation; the tissue echogenicity here is reflective of edematous breast tissue and inflammation. Various other common appearances include necrosis of the axillary nodes with caseous pathology with conglomeration, focal or diffuse skin thickening or fistula formation. If there is abscess formation which fistulizes to the skin, the fistula tract may additionally be visible with ultrasound [10].
Computerized tomography (CT) and magnetic resonance imaging (MRI) are considered higher diagnostic modalities and helpful with the analysis of deep retromammary localization of the breast lesions and associated chest wall involvement. Communication of the fistula tract with pleural membranes, bone and underlying deep soft tissues of the chest can be determined accurately with these imaging modalities.
Biopsy constitutes the gold standard for categorization of the lesions as they show necrotizing inflammation with granulomatous and Langerhans's cells. These also show predominance of acid fast tubercular bacilli (AFB) diagnosed with the Ziehl-Neelsen stain, thus confirming the diagnosis [11]. There is no medical treatment specific to tubercular mastitis with anti-tubercular treatment forming the backbone of treatment strategy lasting for about six to eighteen months. With emerging resistant strains, the treatment is extended until twenty four months. Surgery (lumpectomy or mastectomy) is additionally a possibility once there is no response to medical treatment betting on the surgeon's preference [12]. Abscesses can be effectively treated with ultrasound-guided external evacuation.

Conclusions
We report a rare case of primary tubercular mastitis in a multiparous female with recurring inflammatory breast masses progressing to breast abscess, overlying skin thickening and multiple sinus formation. Such cases mimic pyogenic abscess and carcinoma in their clinical presentation and imaging findings and need to be diagnosed via a myriad of diagnostic tests including interferon assay for tuberculosis, serial ultrasounds and mammograms with histopathology proving the last nail in the diagnosis. Presence of caseating granulomas with granulomatous tissue inflammation with the tissue samples testing positive for acid fast bacilli on Ziehl-Neelsen staining forms a gold standard. The treatment comprises of anti-tubercular treatment up to 24 months depending on individual response or surgery if required. Such a clinical presentation must warrant a differential of granulomatous mastitis in cases of non-responders to incision and drainage and antibiotic therapy.

BIRADS
Breast Imaging Reporting And Data System ATT Anti-Tubercular Treatment FNAC Fine-Needle Aspiration Cytology OPD Outpatient Department TB Tuberculosis