Cytomorphological features of cystic neutrophilic granulomatous mastitis on ThinPrep

Abstract

Granulomatous mastitis (GM) is an uncommon entity and challenging to distinguish from breast carcinoma, both clinically and upon imaging. Cystic neutrophilic granulomatous mastitis (CNGM) is a histologically distinct GM with clear “cystic” spaces (CS) surrounded by neutrophils and may contain Gram‐positive bacilli (such as Corynebacterium species). Cytologic features of GM, in particular CNGM, on ThinPrep (TP), are limited. We reviewed the cytological features of GM with a special focus on CNGM on TP. Ten cases with a concurrent/recent FNA and histologic diagnosis of GM or CNGM, or positive culture for Corynebacterium kroppenstedtii, were identified over an 11‐y period (2007‐2017). A double‐blinded review of the TP slides was performed by two independent cytopathologists. Data were analysed using Fisher's exact test. Six cases were histologically proven CNGM and 1 FNA only case had a positive culture for C. kroppenstedtii. Three had a histological diagnosis of GM. TP from the 7 CNGM cases demonstrated CS, including 1 case with a cellblock (CB) study showing well‐formed clear CS, while none of the non‐CNGM cases had CS (P = .01). Bacteria were identified within CS in 5 of 7 cases of CNGM. Multinucleated giant cells, granulomas, histiocytes, and neutrophils were variably observed. All histologically confirmed cases of CNGM showed distinct CS on TP. Cellblock study is a valuable adjunct to evaluate CNGM and for ancillary studies. Although our study was limited by a small sample size, our findings necessitate the need for studies with a larger cohort.

Cystic neutrophilic granulomatous mastitis: A case report

“…Nevertheless, a large proportion of cases remain unexplained; hence the terminology "idiopathic granulomatous mastitis" is often used [3] . CNGM is a distinct histologic pattern within the entity described as "granulomatous mastitis" [4] . Granulomatous inflammation with suppuration and vacuolated spaces, consistent with dissolved lipid, surrounded by neutrophilic inflammation.…”

“…In addition, it can persist or recur leading to abscess and sinus tract formation [4] . The role of Corynebacterium, a Gram-Positive bacillus, in invasive infections is often discussed since most of these species are part of the endogenous skin flora [5] .…”

Idiopathic Granulomatous Mastitis: Diagnosis and Histopathologic Features, A Review

“…[30][31][32] The characteristic morphologic feature of CNGM is a suppurative lipogranuloma with empty spaces surrounded by successive layers of neutrophils and epithelioid histiocytes (see Figure 4.B). 33,34 The most distinctive feature of CNGM is the identification of a lipophilic rod-shaped gram-positive bacillus from the Corynebacterium genus. 12 The most common isolates are C. kroppenstedtii, followed by C. amycolatum, and C. tuberculostearicum.…”

Clinical characteristics and therapeutic strategy of granulomatous mastitis accompanied by Corynebacterium kroppenstedtii: a retrospective cohort study

“…MALDI-TOF MS has largely supplanted gene sequencing due to the higher cost, greater technical complexity, and prolonged turnaround time associated with gene sequencing [21,22]. Recently, there has been increasing evidence of an association between corynebacterial infection and a distinct pattern termed cystic neutrophilic GM, characterized by lipogranulomas consisting of clear spaces rimmed by neutrophils and surrounding granulomatous inflammation [17,[23][24][25][26][27][28]. However, nearly all of these studies focused on pathological microorganisms, and few studies analysed the clinical features and the best treatment methods of GM patients infected with C. kroppenstedtii.…”