A Case of Cystic Neutrophilic Granulomatous Mastitis in Which Mycobacteroides abscessus Was Detected

Abstract

Introduction: Cystic neutrophilic granulomatous mastitis (CNGM) is characterized by granulomas with cysts that sometimes contain bacteria in the lumen, a surrounding neutrophilic infiltrate, and Langhans giant cells. There are no universally accepted diagnostic criteria for CNGM. Corynebacterium kroppenstedtii, a Gram-positive bacillus, has been reported to cause several infections, but the exact cause remains unclear. We report our experience with a case of CNGM, thought to be due to a rare Mycobacteroides abscessus infection.

Case presentation: We report the case of a 36-year-old Japanese woman with granulomatous mastitis due to Mycobacteroides abscessus who had not undergone surgery and was not immunosuppressed. She presented with a chief complaint of pain and swelling in her left breast for 1 month. Mammography showed asymmetrical focal increased density, and ultrasonography showed an irregular hypoechoic area in the left 3 o'clock position. Contrast-enhanced magnetic resonance imaging showed segmental non-mass-enhancement. Ultrasound-guided vacuum-assisted biopsy with pathology revealed granulomatous mastitis. Ziehl-Neelsen staining revealed red-staining bacilli. The patient was followed up for observation because her breast pain had decreased after the examination, and there was no redness or fever. However, the breast pain has not completely disappeared, and intermittent purulent discharge from the biopsy site persisted for 5 months. Hence, two 12-Fr drains were inserted along the ductal dilatation-like hypoechoic area. Imipenem, amikacin, and clarithromycin were administered for 8 days. After 8 days of this therapy, the patient developed a drug-associated rash; therefore, antimicrobial therapy was discontinued, and the drains were removed. Her symptoms improved, and magnetic resonance imaging after 1 month showed that the previous imaging findings in her left breast had disappeared. At the time of writing, 18 months have passed since treatment, and no recurrence has been observed.

Conclusions: We experienced a rare case of CNGM associated with Mycobacteroides abscessus. This case suggests that a combination of drainage and antimicrobial therapy may shorten the duration of antimicrobial therapy in CNGM.

Keywords: Mycobacteroides abscessus; antibacterial therapy; cystic neutrophilic granulomatous mastitis; drainage; magnetic resonance imaging; ultrasound-guided vacuum-assisted biopsy.

Fig. 1. Mammography findings in a case of cystic neutrophilic granulomatous mastitis caused by Mycobacteroides abscessus. The image shows an asymmetrical focal increased density in the left breast. No evidence of tumor calcification is visible.

CC, craniocaudal; L, left; MLO, mediolateral oblique view; R, right

Fig. 2. Ultrasonographic imaging findings in a case of cystic neutrophilic granulomatous mastitis caused by Mycobacteroides abscessus. (A and B) Ultrasonographic images showing an irregular hypoechoic area extending over the map to replace the mammary tissue in the left breast at the left 3 o’clock position. The hypoechoic area extends partially to just below the skin. (C) The Tsukuba elasticity score was 5, suggesting malignancy. (D) Color Doppler image showing increased blood flow signals around dilated ducts.

Fig. 3. Contrast-enhanced MRI in a case of cystic neutrophilic granulomatous mastitis caused by Mycobacteroides abscessus. (A–C) Contrast-enhanced MRI showing a segmental non-enhanced area measuring approximately 36 × 29 × 89 mm. The contrast pattern increased progressively. Diffusion-weighted imaging shows a high signal intensity, and apparent diffusion coefficient mapping shows some low-intensity signals, strongly suspicious for DCIS or invasive carcinoma with a predominant intraductal component.

DCIS, ductal carcinoma in situ; MRI, magnetic resonance imaging.

Fig. 4. Histopathological findings in a case of cystic neutrophilic granulomatous mastitis, associated with infection caused by Mycobacteroides abscessus. (A) Breast core biopsy results showing large (right side) and small (surrounding the large cyst)suppurative granulomas that are composed of central lipid vacuoles (cysts) rimmed by neutrophils and an outer cuff of epithelioid histiocytes including Langhans-type giant cells (hematoxylin and eosin, ×10). (B) Ziehl–Neelsen staining showing red-stained bacilli (yellow arrowhead) (×100). Granulomatous tissue is seen on the right side.

Fig. 5. MRI 1-month post-antimicrobial therapy showing that the previous findings in the left breast had disappeared.