Multiple skeletal Mets Strongly ER positive BC originally now showing as TNBC
originally diagnosed IDC grade 2 , stage 3A HR+ with Allred score 8/8 and HER2- at the age of 46, 10 years back . Surgery, chemo and radiation therapy done as part of treatment followed by 5 years of tamoxifen followed by 5 years of letrozole and Zolenic acid. Now got bone pain few months back. When done pet scan and MRI shows multiple skeletal sclerosis . Confirmed as bone metastases . Bone biopsy came back as TNBC :( they told it’s ER PR discordant . When went for second opinion one of them said bone biopsy can sometime show false negatives. When checked with lab they said they had used Formic acid for decalcification. However doctor is suggesting to start Chemo treating it as TNBC. I am so confused and don’t know how to proceed . Anyone had similar situation with Bone Mets?
Comments
-
@warriortowin I'm so sorry to hear this is happening to you. It's so very stressful, especially when findings seem uncertain. My heart goes out to you. I can't really give you any advice myself on your question, but if it were me, I would seek a second opinion, especially if you are not at a major cancer center. It can't hurt, and might alleviate the uncertainty.
3 -
thank you @tougholdcrow 💗
0 -
prefacing by saying that ChatGPT may be wrong but according to what it says you need a second opinion or another test to validate the tnbc …
ChatGPT says as follows
Key facts in your situation (important)
- Original cancer: IDC, ER/PR strongly positive (Allred 8/8), HER2-, stage IIIA
- Long disease-free interval: ~10 years (this matters a LOT)
- Metastasis site: bone only, sclerotic lesions
- Bone biopsy: ER/PR negative (TNBC)
- Formic acid decalcification used → known to cause false ER/PR negatives
1️⃣ Is receptor “switching” possible?
Yes — but context matters.
- ER → negative discordance happens in ~10–20% of metastases
- True switch to TNBC after 10 years of endocrine sensitivity is uncommon
- When it does happen, it’s usually:
- After multiple prior lines of metastatic therapy
- Or with visceral, aggressive relapse
Your relapse pattern (bone-only, long latency, sclerotic lesions) biologically looks HR-driven, not TNBC.
2️⃣ The decalcification issue is NOT minor
This is critical.
Formic acid decalcification is well known to:
- Destroy ER and PR epitopes
- Produce false-negative hormone receptor results
- ASCO/CAP guidelines explicitly warn about this
👉 Many major cancer centers do not trust ER/PR negativity from formic-acid–decalcified bone biopsies.
This is why one oncologist told you it may be a false negative — they are correct.
3️⃣ Why this matters so much
Because treatment paths diverge completely:
If treated as TNBC:
- IV chemotherapy
- Faster toxicity
- Shorter disease control on average
- No endocrine options
If treated as HR+ metastatic disease:
- Endocrine therapy ± CDK4/6 inhibitor
- Often years of disease control
- Much better quality of life
This decision is not trivial.
4️⃣ What most breast cancer experts would consider reasonable here
Given:
- Strong original ER (8/8)
- 10-year endocrine responsiveness
- Bone-only relapse
- Known technical risk of false negative biopsy
👉 Many experts would NOT rush to label this as true TNBC without further confirmation.
5️⃣ Reasonable next steps (very important)
You are not being difficult by asking for these — this is standard at top centers.
Option A (best if feasible)
Repeat biopsy:
- From non-bone site if any exists
- Or bone biopsy using EDTA decalcification (not formic acid)
Option B (if re-biopsy not feasible)
- Treat as HR-positive disease initially
- Monitor response closely
- Switch to chemo only if endocrine therapy fails quickly
This approach is commonly used when biology and biopsy conflict.
6️⃣ Questions you should ask your oncologist (you can copy-paste)
- How confident are we that ER/PR negativity is real given formic acid decalcification?
- Would NCCN/ASCO consider this result definitive?
- Can we repeat the biopsy using EDTA decalcification or sample another site?
- Given the 10-year endocrine response and bone-only disease, is a trial of endocrine therapy reasonable?
- What would make you switch to chemotherapy?
If your oncologist dismisses these concerns outright, that itself is a reason for another opinion (preferably at an academic cancer center).
7️⃣ Emotional truth (important)
Nothing about this means:
- Your original treatment failed
- You did something wrong
- This was “inevitable”
Late bone relapse after HR+ breast cancer is unfortunately a known biological behavior, even after doing everything right.
Bottom line
- Your confusion is medically justified
- Bone biopsy ER/PR negativity after formic acid decalcification is not fully reliable
- Given your history, it is reasonable — and often preferred — to confirm before committing to TNBC chemotherapy
- A cautious, biology-respecting approach is supported by expert practice
If you want, I can:
- Help you decide how urgent chemo truly is
- Walk you through what an endocrine-first trial would look like
- Help you prepare for a third opinion at a major cancer center
You don’t have to rush this decision blindly.
0 -
I got the same suggestions from chat gpt when I searched but was scared if it was truly TNBC 😢😢 doctor started first chemo
0
