Cystic neutrophilic granulomatous mastitis: Focus on preoperative cytology and intraoperative consultation

Abstract

Cystic neutrophilic granulomatous mastitis (CNGM) is a rare and distinctive variant of mastitis. 1 The clinical presentation and imaging features can be suggestive of a malignant tumor, potentially leading to unnecessarily aggressive surgical intervention. 2 Accurate preoperative diagnosis is therefore critical. On gross examination, the mass lesion was irregular and firm (Figure 1B), and formalin-fixed paraffin-embedded sections showed well-developed noncaseating granulomas containing cyst-like empty spaces. [...]we report a rare case of CNGM from Taiwan, and assume that this unique disease has previously been underappreciated in Asian countries.

Cystic neutrophilic granulomatous mastitis (CNGM) is a rare and distinctive variant of mastitis.¹ The clinical presentation and imaging features can be suggestive of a malignant tumor, potentially leading to unnecessarily aggressive surgical intervention.² Accurate preoperative diagnosis is therefore critical. Although the histological features of CNGM are well-documented, it has rarely been reported in Asian countries.

A 35-year-old female presented to our surgery department with a progressively enlarging right breast lump over several weeks. Initial physical examination detected a palpable breast mass in the upper medial quadrant, with erythema, warmth and tenderness on palpation. She was afebrile, with an unremarkable medical history. The patient denied trauma, breast-feeding, or pregnancy within a year. On sonography, a solitary heterogeneous nodule of up to 8.0 cm with an irregular and indistinct border was identified. Microcalcifications were present (Figure 1A), and multiple axillary lymph nodes of up to 1.3 cm were identified. The lesion was classified as BI-RADS category 5, highly suspicious for malignancy. The cytology of FNA specimens revealed multinucleated giant cells associated with numerous neutrophils, and the mass was interpreted as a suppurative and granulomatous lesion.

FIGURE 1. (A) A heterogeneous hypoechoic tumor-like lesion with ill-defined border was identified by ultrasound. (B) The mass was firm and irregular on gross examination. Histology of permanent section (C,D) showed characteristic neutrophil-rich granuloma formation and cyst-like spaces (arrow)

To obtain tissue for a definite diagnosis, open surgery with intraoperative consultation was indicated. A frozen section confirmed a neutrophil-rich granulomatous reaction. Lumpectomy was performed without lymph node dissection. On gross examination, the mass lesion was irregular and firm (Figure 1B), and formalin-fixed paraffin-embedded sections showed well-developed noncaseating granulomas containing cyst-like empty spaces. These round to oval-shaped spaces varied greatly and were surrounded by neutrophils (Figure 1C,D). In both Giemsa and Gram stains, very few bacilli were observed exclusively within the aforementioned cyst-like spaces. Acid fast, PAS, and GMS stains were negative, and microorganism cultures failed to isolate any causative infectious agent. The histopathological findings were characteristic of CNGM. After surgical excision followed by oral cephradine antibiotic treatment, complete resolution was achieved.

To date, CNGM has mostly been reported in Western countries, and an association with Hispanic ethnicity is suggested.^3,4 It occurs most frequently in women in their 20 to 40s.^3–5 Corynebacterium is associated with this unique disease. To the best of our knowledge, this is the first report of CNGM in Taiwan.

Despite being benign, CNGM often presents as a worrisome mass lesion of BI-RADS category 4 or more.^2,5 A large irregular or spiculated hypoechoic mass is a frequent finding,^2,5 and a distinctive pattern of suppurative and granulomatous inflammation without necrosis in FNA specimens or intraoperative frozen sections is indicative of CNGM. Definitive treatment often requires prolonged antibiotic medication in combination with repeated debridement.² Therefore, we propose initial complete surgical removal followed by prophylactic antibiotics to treat CNGM.

In conclusion, we report a rare case of CNGM from Taiwan, and assume that this unique disease has previously been underappreciated in Asian countries. Often noted to have a suspicion of malignancy, CNGM can be identified from FNA cytology or intraoperative frozen sections. Complete removal of the lesion with postoperative antibiotics is an ideal treatment option to achieve resolution.

CONFLICT OF INTEREST

The authors declare no conflict of interest.