The edition · Pathology
Phyllodes tumours: count stromal mitoses in the hotspot
International breast pathologists set out a standard for the mitotic count that decides a phyllodes grade. Plus the zone 3 pattern of CDK4/6 inhibitor liver injury, a BAP1-linked vulvovaginal tumour and confocal margins in Mohs surgery.
The edition in brief
Today's pathology edition ends on grading phyllodes tumours. A Histopathology paper from an international group of breast pathologists (8 October) recommends counting stromal mitoses in the most active area — the hotspot — rather than averaging across fields, with the count normalised to the microscope's field diameter, to make benign, borderline and malignant grading more reproducible. A single-centre series of seven women with metastatic breast cancer and biopsy-characterised CDK4/6 inhibitor liver injury, six on ribociclib, found acute hepatitis with perivenular (zone 3) confluent necrosis and lymphocytic cholangitis; ANA positivity in three did not reflect autoimmune hepatitis, and all recovered after withdrawal. A four-case report in the American Journal of Surgical Pathology describes a vulvovaginal epithelioid mesenchymal neoplasm with deciduoid morphology, oestrogen and progesterone receptor positive, two of which had BAP1 loss with germline BAP1 variants. A prospective study of 261 Mohs margins found ex vivo fluorescence confocal microscopy agreed with histology in 96.4% and between dermatologist and pathologist readers almost perfectly. The pearl is the drug timeline on every liver biopsy request.
CDK4/6 inhibitor liver injury: zone 3 necrosis and lymphocytic cholangitis, resolving on withdrawal
In a woman on a CDK4/6 inhibitor with acute hepatitis, zone 3 necrosis with lymphocytic cholangitis supports drug-induced injury; do not let a positive ANA redirect the diagnosis.
A deciduoid vulvovaginal tumour that can point to germline BAP1 variants
Stain a deciduoid, ER/PR-positive vulvovaginal mesenchymal tumour for BAP1, and refer for genetics if it is lost.
Confocal microscopy matched histology on 96% of Mohs margins
In trained hands, ex vivo confocal microscopy reliably assessed Mohs margins, but it still missed one positive margin in 261.
Put the drug timeline next to every liver biopsy
Get the drug history and dates before reporting a medical liver biopsy, and say whether the pattern fits drug injury.
Count phyllodes stromal mitoses in the hotspot, normalised to field area
Grade phyllodes tumours using a hotspot stromal mitotic count normalised to field area, and state the method in the report.
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