Optimizing the pathological diagnosis of diffuse malignant peritoneal mesothelioma.

BACKGROUND

Diffuse malignant peritoneal mesothelioma (DMPM) is the most common histological type of peritoneal mesothelioma (PM). Accurate histology and Ki67 assessment are crucial for treatment and prognosis, yet intra-tumoral heterogeneity may hinder preoperative diagnostics. A standardized diagnostic pathway is lacking. This study evaluates factors influencing the diagnostic accuracy on Ki67 and sarcomatoid component.

MATERIALS AND

METHODS

This retrospective study analysed 98 patients (2008-2022). Concordance between preoperative and post-CRS-HIPEC histological subtype and Ki67-class (≤9 % vs. >9 %) was estimated using the k-index. Fisher's exact test assessed the impact of biopsy type (core-needle vs. surgical), biopsy number (single vs. multiple), and specimen quantity (slides and blocks) on histotype and Ki67 concordance. Diagnostic performance was evaluated for both core-needle and surgical biopsy.

RESULTS

Concordance was moderate for Ki67 (k-index = 0.4) and optimal for histotype (k-index = 0.8). No significant differences were found between biopsy types for histotype (p = 0.60) or Ki67 (p = 1.00). Diagnostic accuracy was unaffected by biopsy number (p = 0.16 histotype, p = 0.50 Ki67) or volume (p = 0.30 histotype, p = 0.60 Ki67). Surgical biopsy had Sensibility (Se) = 80 %, Specificity (Sp) = 98 %, Positive Predictive Value (PPV) = 80 %, Negative Predictive Value (NPV) = 98 % for sarcomatoid identification, and Se = 86 %, Sp = 82 %, PPV = 79 %, NPV = 88 % for Ki67. Core-needle biopsy showed Se = 60 %, Sp = 100 %, PPV = 100 %, NPV = 50 % for Ki67.

CONCLUSIONS

Surgical biopsy remains the current gold standard for PM diagnosis, but core-needle biopsy could be considered for lesions accessible via interventional radiology.