melina path

residente en anatomie pathologique

[Anjali Pandey @AnjaliP89497956]

Series 6: Phyllodes tumors still surprise us: 2026 updates.

Post 3 : Gross , Histopathology, & Sampling .

⏩Grossly : well- defined , bosselated, often multinodular masses with fleshy , cleft like cut surfaces . Tongues of tumor into the parenchyma suggest invasion , and hemorrhage and necrosis correlate with malignancy .
➖The key problem is heterogeneity . About 1/3rd of PTs container years that , taken alone , look like fibroadenoma . High grade foci and heterologous elements can be small.

⏩Sampling :
- at least 1 block per cm of the largest dimension
- 2 blocks per cm of the gross appearance is heterogeneous or the diagnosis is uncertain.
- sample margins extensively when breast conservation is planned
- use synoptic reporting
- sampling hasn't been standardized , so this is expert consensus .

⏩The core biopsy challenge:
A core biopsy says " fibroadenoma" How sure can you be ?

- accuracy across studies : 13-84%
- false negative rate 25-30% , underestimation 18.8-37.5%
- In one 455- lesion series, 19.7% of fibroepithelial lesions were upgraded to PT.
- Fewer than 1% of PTs are missed when radiologic pathologic correlation is good.

➖Clues towards PT :
- rapid growth , larger size , heterogeneous ultrasound
- prior fibroadenoma surgery
- stromal predominance or overgrowth
- bipolar nuclei in the background favor fibroadenoma, while stromal fragmentation points to borderline or malignant PT .

⏩Is WHO's " full house" too strict ?
WHO 5th edition required all 5 features for malignant :
1. marked atypia
2. overgrowth
3. 5 or more mitoses/ mm2 , marked diffuse cellularity , and a permeative border.

⚠️The concern is undercalling . 44% ( 22 of 50 ) of PTs with distant metastases would have been called borderline .

⚫ Alternatives :
1. WHO 6th edition ( 2026): four of five features
2. Refined Diagnostic Criteria (RDC) : malignant if overgrowth plus one other features, or marked cellularity plus one other

In a 136 case validation :
-76% classified the same by both systems .
- RDC called 75 tumors malignant vs 42 by WHO
- WHO borderline tumors metastasized in 9 of 94 ( 10% ) , RDC borderline in 0 of 61.

The trade off : about 60% of RDC malignant tumors won't metastasize , so some patients may be over labeled . The authors say more validation is needed .

#BreastPathology #WHOClassification #WHO6 #RDC #DiagnosticPathology #PhyllodesTumor #Histopathology

[Janira Navarro @Janiranavarro]

Is this flat epithelial atypia (FEA)?

No, this is columnar cell hyperplasia
CK 5/6: It is negative like FEA
ER: Positive

Dr. Allison. 2026 Diagnostic Pathology Update #USCAP #pathology #PathX

[Janira Navarro @Janiranavarro]

Breast papillary lesions: Key Features Overview

Dr. Allison. 2026 Diagnostic Pathology Update. #USCAP #pathX #pathology

[Janira Navarro @Janiranavarro]

Ovary – Changes to WHO Classification (6th edition, 2026)
Serous borderline ovarian tumors:
The terms “microinvasion” and “microinvasive” are no longer recommended

What was previously called microinvasion (single cells and clusters of cells with eosinophilic cytoplasm and low-grade nuclear features) has no clinical significance (see pic 2). It can be mentioned in a comment if desired; Dr. Gilks previously reported it but no longer does

What was previously called microinvasive carcinoma represents small foci of low-grade serous carcinoma (see pic 3). Report the size and extent of these foci and diagnose them as a small focus of low-grade serous carcinoma arising in a serous borderline tumor

Dr. Gilks. Gynecologic Pathology Masterclass 2026
#USCAP #pathology #pathX

[Janira Navarro @Janiranavarro]

How to differentiate between adenoid cystic carcinoma and basaloid squamous cell carcinoma?

p40 stains basal/myoepithelial cells only in ACC and is diffuse in SCC.
Pitfall ⚠️: SOX10 and MYB IHC can be positive in both.

Dr. Nishino - 2025 Diagnostic Pathologic Update #USCAP #pathology #PathX

[Miruna Popescu, MD @MirunaPopescu13]

Recognizing pT4a in CRC is important
➡️ Tumor continuous w/ serosal surface through loose inflammation/granulation tissue = pT4a
➡️ Tumor separated from serosa only by non-inflamed fibrosis = pT3
➡️ Tumor <0,1 mm from serosal surface, but not continuous through granulation tissue/loose inflammation = pT3 (as recommended by CAP), but these seem to behave like pT4a

Dr. Rish Pai, #HMAR_DIGESTIVE26
#gipath #pathtwitter

[Brett Baskovich, MD @drdoubleb]

These are getting good (by ChatGPT)

[Dr. Arkadip MD @pathognosis22]

#PTC A Concise note on papillary thyroid carcinoma with all her variants #OC #Pathognosis #Pathology #Endocrine #Endopath

[Dr. Arkadip MD @pathognosis22]

#papillary neoplasm of #breast #OC #pathognosis #breastpath

[MV Chandrakanth @ChandrakanthMv]

MMR proteins — the simplest way to remember
DNA replication often makes small mistakes (extra or missing bases).
The mismatch repair (MMR) system fixes these errors in two steps:
🔍 MSH2 + MSH6 → detect the error
🔧 MLH1 + PMS2 → repair the error
They work together as a single pathway — first detection, then repair.
If this system fails → errors accumulate → dMMR
And that’s where microsatellite instability (MSI) begins.
Bottom line:
Detection first → then repair
#MVOnco #Oncology #MedEd

[Charlie Herndon @DrCycloPath]

Question 2: The correct IHC profile is Strong, diffuse ER positivity; negative for CK5/6.

#PathTwitter #Pathology #BreastPath
WSI: https://t.co/dF0ROphc7O
Learn more: https://t.co/jEnYok7tYI

[Samson W. Fine, MD @rovingatuscap]

Stunning contrast between flat urothelial carcinoma in situ (right side of each image) and reactive urothelium (left side)

CIS➡️enlarged, irregular, &amp; hyperchromatic nuclei

Reactive➡️small, uniform nuclei w/vesicular chromatin + intraepithelial acute &amp; chronic inflammation

[Janira Navarro @Janiranavarro]

Breast
Histologic Variants of Invasive Lobular Carcinoma (ILC)
-Many of these variants coexists and could be difficult to separate one from the other
New variants (WHO 6th edition)
-ILC with extracellular mucin
-ILC with solid papillary growth

Dr. Sahin #USCAP25 #pathology #PathX

[Samson W. Fine, MD @rovingatuscap]

Urothelial carcinoma with micropapillary features displaying multiple small to medium sized nests lacking fibrovascular cores, situated within lacunar spaces

[Behnas Malek F.Z @malakbehnas]

Lichen simplex chronicus 🔬

✔️Chronic dermatitis characterized by localized areas of thickened skin resulting from chronic scratching
✔️Orthokeratosis with focal parakeratosis
✔️Hypergranulosis
✔️irregular acanthosis
✔️Papillary dermal fibrosis

#dermpath #Xpath

[Charlie Herndon @DrCycloPath]

Pap from a 60-year-old woman, history of ASC-US. What is your interpretation?
A) NILM
B) ASC-H
C) HSIL
D) Non-keratinizing SCC
#Cytopathology #CytoPath #PathTwitter #Pathology

[Lorena Villarreal @lorenaevilla]

Thyroid resection. #groos #theartofgrossing #pathology #PathTweetaward #pathTwitter #pathologist

[melina path @nari_melina]

https://t.co/3ByAgt9ZOA

[Lorand Kis @kis_lorand]

@Carol2Path the original publication from the LAST project 👇👇 https://t.co/UqzKq6bhpk

[Janira Navarro @Janiranavarro]

Neuroendocrine neoplasms can be separated in 3 groups-IARC/WHO Taxonomy
Epithelial NEN
Non-epithelial NEN
Paraganglioma-like NEN

Dr. Mete #USCAP25 #pathology #PathX