Clinical question This is a case of an elderly woman who presented symptomatically and on examination was found to have a multifocal breast cancer. An ultrasound-guided axillary node biopsy was carried out.
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What is your diagnosis?
DCIS in axillary breast tissue with dense lymphocytic infiltrate
Metastatic carcinoma of the breast with DCIS-like morphology
Primary carcinoma in axillary tail breast tissue
Primary carcinoma arising in ectopic breast tissue in the axillary node
Primary invasive carcinoma with DCIS and lymphocytic infiltrate
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Discussion This core biopsy shows nodal tissue with well-circumscribed islands of malignant cells showing central comedo necrosis and focal calcification. The appearances resemble solid ductal carcinoma in situ (DCIS) with luminal calcifications and comedo necrosis. However, careful examination reveals absence of a myoepithelial layer around the malignant islands. No normal mammary tissue is identified to suggest origin from axillary breast tissue. No benign inclusions are noted within the nodal tissue.
The features are those of metastatic mammary carcinoma with DCIS-like morphology (also referred to as reversed DCIS pattern). The ductal-like structures with central comedo necrosis and calcification are not true DCIS. This pattern of metastasis has previously been described in few reports.1 2 It can be seen in axillary node clearances for metastatic carcinoma and is less commonly seen on core biopsies. Smooth muscle immunohistochemistry (such as smooth muscle myosin, p63) confirmed the absence of a myoepithelial layer. Awareness of this entity is important to avoid a mistaken diagnosis of DCIS or primary carcinoma which would alter patient management.
The patient subsequently underwent mastectomy and axillary node clearance. A large single grade 3 triple negative metaplastic carcinoma was confirmed. Two of the axillary nodes showed metastatic carcinomas. These exhibited the same DCIS-like pattern identified on the diagnostic core biopsy.
Benign inclusions within axillary nodes can be of glandular type, squamous, mixed3 or non-epithelial (eg, naevus cells). These are normally seen in the capsular or subcapsular area and lack atypia.
- breast cancer
- lymph node pathology
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Handling editor Iskander Chaudhry.
Contributors ME searched the literature and wrote the first draft. AMS diagnosed and selected the case. Both authors contributed to the writing up and approval of the final manuscript.
Competing interests None declared.
Patient consent Not required.
Provenance and peer review Commissioned; internally peer reviewed.
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