Suggested diagnostic criteria for CNGM (A) and canned comments (B) to convey degrees of diagnostic certainty in pathology reports
| A | ||
| 1. Histology | 2. Gram stain on tissue section | 3. Microbiology (culture or molecular testing) |
| 1.1. Lobulocentric inflammation | 2.1. Coryneform GPB | 3.1. Positive for corynebacteria |
| 1.2. Cystic spaces rimmed by neutrophils | 2.2. Non-coryneform GPB | 3.2. Positive for organisms other than corynebacteria |
| 1.3. Granulomas | 2.3. Gram negative organisms | 3.3. Negative for organisms |
| 2.4. Mixed Gram positive and negative organisms | ||
| 2.5. Negative for organisms |
| B | Diagnostic criteria | Interpretation | Pathology report |
| A | (1) 2–3 of 3 features AND (2) 2.1 OR (3) 3.1 | Characteristic morphology with GPB or positive culture | Diagnosis: Findings consistent with CNGM (see comment). Comment: The morphology combined with GPB on Gram stain is consistent with CNGM. Microbiological culture for corynebacteria may be considered. (include results of culture if performed) |
| B | (1) 2–3 of 3 features AND (2) 2.2 to 2.5 OR (3) 3.2 to 3.3 | Characteristic morphology without GPB or positive culture | Diagnosis: Findings suggestive of CNGM (see comment) Comment: The morphological features are suggestive of CNGM. However, Gram stain shows no evidence of GPB indicative of Corynebacterium species typically associated with CNGM. As corynebacteria are fastidious organisms, the absence of supportive microbiological evidence should not immediately exclude infection as a cause. The differential diagnosis includes other granulomatous diseases of infectious and non-infectious aetiology. Clinical and microbiological correlation is required. Microbiological culture for corynebacteria may be considered. (include results of culture if performed) |
| C | (1) Any of the 3 features AND (2) 2.1 OR (3) 3.1 | Suspicious clinical and morphological features with GPB or positive culture (limited sample, for example, core biopsy) | Diagnosis: Granulomatous inflammation with bacterial forms (see comment) Comment: The morphological features are suggestive but not diagnostic of CNGM. Gram stain shows evidence of GPB indicative of Corynebacterium species typically associated with CNGM. The differential diagnosis includes other granulomatous diseases of infectious and non-infectious aetiology. Clinical correlation is required. Microbiological culture for corynebacteria may be considered. (include results of culture if performed) |
| D | (1) Any of the 3 features AND (2) 2.2 to 2.5 OR (3) 3.2 to 3.3 | Suspicious clinical and morphological features without GPB or positive culture (limited sample, for example, core biopsy) | Diagnosis: Granulomatous inflammation (see comment) Comment: The morphological features are those of granulomatous mastitis. Special stains (Gram, GMS, PASD, ZN) show no evidence of micro-organisms. The differential diagnosis includes CNGM and other granulomatous diseases of infectious and non-infectious aetiology. Clinical and microbiological correlation is required. Microbiological cultures, including corynebacteria, may be considered. (include results of culture if performed) |
.CNGM, cystic neutrophilic granulomatous mastitis; GMS, Grocott's Methenamine Silver; GPB, gram-positive bacilli; PASD, Periodic acid-Schiff diastase; ZN, Ziehl-Neelsen.