WHO Dis?
Neuroendocrine neoplasms of the breast are now strictly harmonized with other organ systems, divided into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs) based on these two histologic features
What are mitotic count and Ki 67 proliferation index (along with necrosis)
I am a spindle cell lesion with infiltrative bounds, mimicking low-grade metaplastic cancer on my clinical rounds. But look for my nuclear expression of this adhesion-linked clue.
What is Beta-Catenin?
In high-grade cancers that are triple-negative and mean, you’ll frequently find mutations in this gatekeeper gene.
What is TP53? (Mutated in over 80% of Triple-Negative Breast Cancers).
When determining the Nottingham Histologic Score, this specific architectural feature must be calculated across the entire tumor rather than just focusing on the highest-grade areas.
What is Glandular/Tubule Formation
Under the current framework, "Lobular Carcinoma in Situ (LCIS)" is classified as classical, but these two distinct variants must be specified due to their significantly higher risk of upgrade on excision
What are Florid LCIS and Pleomorphic LCIS
To differentiate microinvasive carcinoma from radiation-induced atypia or sclerosing adenosis, this specific double or triple IHC cocktail is preferred to highlight intact vs. lost myoepithelial layers.
What is p63 + Calponin (or Smooth Muscle Myosin Heavy Chain/SMMHC)
I look like a high-grade carcinoma with a pushing, sheet-like design, packed with lymphocytes on the hematoxylin line. Often triple-negative, I mock standard ductal tracks because I hide germline defects in this specific DNA homologous recombination repair complex.
What is BRCA1? (Classically driving triple-negative breast cancers with medullary features, which feature pushing borders, high mitotic rates, and a dense lymphoplasmacytic infiltrate)
This rare tumor mimics an invasive carcinoma or fibroadenoma on gross exam, but histologically consists of nests of cells with abundant granular cytoplasm that are strongly S100 positive and cytokeratin negative.
What is a Granular Cell Tumor?
I used to be "intraductal" in old fashion books, when a fibrous capsule defined all my looks. But the WHO changed my name to be crisp and precise, so check the new manual and look at it twice!
What is Encapsulated Papillary Carcinoma
While E-cadherin loss points to lobular neoplasia, a false-negative (aberrant positive) membranous staining can occasionally be seen in lobular cells due to this specific catenin complex alteration
What is p120-catenin (which shows cytoplasmic, rather than membranous, localization in lobular neoplasia)
Patients with Cowden syndrome possess a germline mutation in PTEN, which physically leads to the upregulation of this critical metabolic survival pathway in breast tissue.
What is the PI3K/Akt/mTOR pathway?
To differentiate mammary Paget’s disease from cell-for-cell mimics like Toker cells or squamous cell carcinoma in situ, Paget cells show a distinct immunophenotype, which is?
they are strongly positive for CK7, HER2 and CAM5.2 (or CK8/18)
While other malignant heterologous elements upgrade me to a malignant fate, I am a specific differentiation whose standalone status was downgraded by the WHO update.
This GATA3-positive, highly aggressive triple-negative variant classically displays a nested, sheet-like, or syncytial growth pattern with prominent lymphocytic infiltrates.
What is Medullary Carcinoma (or TNBC with medullary features)
I’m a clear cell mimic that looks like melanoma on a plate, but a balanced translocation determines my true genetic fate. Look for t(12;22) to see where my fusion is done, merging the gene ATF1 with EWSR1.
Primary Clear Cell Sarcoma of the breast
Though breast tissue is present in the anatomy of men, it lacks TDLUs nine times out of ten. Because of this structural missing link, this specific historic histological subtype is exceptionally rare to see on a male biopsy brink.
What is Invasive Lobular Carcinoma (ILC)? (Over 90-95% of male breast cancers are Invasive Ductal Carcinomas; classical lobular carcinomas are rare because lobules do not normally develop in the male breast without exogenous estrogen stimulation).
This vascular and hematolymphoid nuclear transcription factor serves as a highly sensitive surrogate immunohistochemical marker for mammary Secretory Carcinoma.
What is ERG?
(While ERG is famous as an endothelial and prostatic marker, it is a well-documented, high-yield diagnostic pitfall because it strongly stains the neoplastic cells of mammary secretory carcinoma).
5 genes associated with BRCA 1 and 2 genes
[BROCA genes]
What is ATM, BRIP1, CDH1, CHEK2, RAD51C, RAD51D, PALB2, PTEN, STK11, TP53