The edition · Pathology
MTAP loss in peritoneal mesothelioma is not a stand-in for CDKN2A deletion
A FISH study finds MTAP and CDKN2A part company in the peritoneum, while Korean guidance standardises ctDNA testing on pleural fluid and lavage, and two studies refine Hodgkin classification and post-neoadjuvant TNBC reporting.
The edition in brief
Today's pathology edition opens on molecular testing. Korean consensus guidelines set out 15 recommendations for circulating tumour DNA testing on pleural effusion and bronchoalveolar lavage fluid in lung cancer, covering pre-analytical handling, validation and reporting; the evidence base is dominated by pleural fluid, and only 21% of surveyed Korean laboratories offer the test. A review of 203 early triple-negative breast cancers after neoadjuvant pembrolizumab-based treatment found 63% pathological complete response and heterogeneous residual and nodal patterns, with recurrence linked to residual nodal disease and low tumour-infiltrating lymphocytes. A dual kappa/lambda mRNA in situ hybridisation study of 53 lymph nodes showed strong cytoplasmic light-chain signal in all typical NLPHL and 80% of borderline cases, but never in classic Hodgkin lymphoma, supporting its use in grey-zone biopsies. The pearl covers sampling the tumour bed after neoadjuvant therapy. The edition closes on a Histopathology study comparing MTAP immunohistochemistry and FISH with CDKN2A FISH: in pleural mesothelioma MTAP loss was 100% specific for CDKN2A deletion, but in peritoneal mesothelioma agreement with CDKN2A was poor (kappa 0.21), so MTAP should be read as a separate marker there rather than a surrogate.
Pleural fluid and lavage ctDNA in lung cancer: 15 recommendations for the lab
Pleural fluid ctDNA can fill a gap when tissue is scarce, but needs matrix-specific validation and a report that states its limits.
TNBC after neoadjuvant chemoimmunotherapy: response is patchy beyond pCR
After neoadjuvant chemoimmunotherapy for TNBC, report residual pattern and nodal response in detail, and record baseline lymphocytes.
Light-chain mRNA ISH separates grey-zone NLPHL from classic Hodgkin
In grey-zone Hodgkin biopsies, strong cytoplasmic light-chain mRNA in tumour cells favours NLPHL; faint signal does not.
Find and sample the tumour bed after neoadjuvant therapy
Locate the clip, measure and map the whole tumour bed, and look for nodal treatment effect before calling a complete response.
Peritoneal mesothelioma: read MTAP loss on its own terms
In peritoneal mesothelioma, interpret MTAP loss as a separate marker of malignancy, not as a proxy for CDKN2A deletion.
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