The edition · Pathology
A third of breast adenomyoepitheliomas were reclassified on review
Twenty-six cases, 35% reclassified, and six core biopsy misinterpretations corrected only at excision — with size and border the features that stratified the spectrum. Plus MTAP losing its surrogate role in peritoneal mesothelioma, and which block to stain for Ki67 in a small bowel neuroendocrine tumour.
The edition in brief
A series of 26 breast adenomyoepitheliomas spanning benign (54%), atypical (27%), special salivary gland-like (12%) and malignant (8%) subtypes was reclassified in 35% of cases. Malignant lesions were larger (median 27.5 mm) and infiltrative; the others were 12 to 18 mm with lobulated contours. Excision corrected six core biopsy misinterpretations, including one metastatic malignant adenomyoepithelioma called a papilloma with ductal carcinoma in situ. Aberrant myoepithelium — loss or heterogeneous p63 and calponin — appeared in 19%. Disease-free survival was 89% over a median 44 months. The authors recommend excision of adenomyoepithelioma-like core biopsy lesions, particularly above 20 mm. A review of inflammatory soft tissue tumours covers inflammatory well-differentiated liposarcoma, angiomatoid fibrous histiocytoma, myxoinflammatory fibroblastic sarcoma, inflammatory myofibroblastic tumour, mass-forming fibroinflammatory lesions and inflamed vascular tumours, on the grounds that some malignant lesions are mistaken for reactive processes. Shallow whole-genome sequencing of 33 TP53-mutated multiple-classifier endometrial carcinomas identified 12 copy-number-high tumours (36.4%), which were more often non-endometrioid, high-grade and advanced-stage. All six recurrences and all three disease-related deaths at a median 12.8 months occurred in that subgroup. In 24 peritoneal mesotheliomas, MTAP immunohistochemistry agreed closely with MTAP FISH (kappa 0.83) but poorly with CDKN2A FISH (kappa 0.21, not significant), against good concordance in pleural mesothelioma. Among 75 jejunoileal neuroendocrine tumours, only mesenteric tumour deposit Ki67 predicted progression (HR 1.22 per 1% increase, 95% CI 1.02-1.46).
Breast adenomyoepithelioma: 35% reclassified, and the core biopsy was usually the problem
Send an adenomyoepithelioma-like core biopsy lesion for excision, especially above 20 mm — a third of this series was reclassified and six diagnoses changed only after excision.
The inflamed soft tissue lesion that is not a reactive process
Write the soft tissue differential into the report for any inflamed lesion presenting as a discrete mass, and get the clinical presentation before calling it reactive.
Copy-number profiling split TP53-mutated multiple-classifier endometrial carcinomas in two
Treat the favourable molecular category of a TP53-mutated multiple-classifier endometrial carcinoma as an algorithmic output, and flag adverse morphology explicitly in the report.
MTAP does not stand in for CDKN2A in the peritoneum
In peritoneal mesothelioma, report MTAP loss on its own terms rather than as a surrogate for CDKN2A deletion, and test CDKN2A directly when its status matters.
Read the internal control before you read the tumour
Read the internal control first: no adequate internal control means the run is uninterpretable, and patchy staining is a reason to repeat rather than a call of loss.
For Ki67 in a small bowel neuroendocrine tumour, stain the largest mesenteric deposit
Stain the largest mesenteric tumour deposit for Ki67 in a jejunoileal neuroendocrine tumour, and say in the report which tissue the index came from.
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