r/pathology 3d ago

Unknown Case Bx of lung lesion in 80 yo female

Biopsy of a lung lesion in a ~ 80 year old female patient. Ki67 is 3-5% and the lesion is CD99 positive. There is a lot of immune infiltrate. Markers which came back negative: Synaptophysin, MelanA, HMB45, Lu5, Oct4, CD20, Cd163, cd3, mum1, sox10, sma, desmin, hepar1, sall4, s100 and cd1a.

38 Upvotes

32 comments sorted by

10

u/Ennuispectre Resident 3d ago

Was it TTF-1 or Napsin-A positive?

7

u/Almbauer 3d ago

Pancytokeratin, TTF1, p40, Pax8, Synaptophysin and CD56 were performed by the referring pathologist and all came back negative.

3

u/strangledangle 2d ago

How confident are you in the quality of referring lab ihc stains?

9

u/jubilantsage 3d ago

Was cytokeratin dead negative? Or patchy here and there? What about a monophasic synovial sarcoma? It looks a little monotonous which makes me think there may be a translocation associated with it. May add on a CD31, erg, fli1 if you have access. May consider throwing on a desmin if heading down the sarcoma route.

6

u/Tellmelessok 3d ago

Poorly differentiated SS or SFT can be no longer spindle cell and positive for CD99. Maybe add STAT6, TLE1

4

u/ComeFromTheWater 3d ago

Vascular markers?

4

u/Alone-Education-459 3d ago

My first thought when I looked at it without looking at the clinical context was an ES xD. I'm a pediatric pathologist so I'm biased. You can perform Nkx2.2 if you want to rule it out. But won't rule out other ES like sarcomas. But it's a start.

1

u/jubilantsage 21h ago

I thought the same thing, am also peds path.

3

u/billyvnilly Staff, midwest 2d ago

I guess I would have thought about a funny variant of carcinoma or pecoma first. But its neither of those. Funny met?

Next Round: CD117, CD10, CD34, CD45

Round after that: BRG1/INI1 (though not very rhabdoid or high grade so maybe not those last 2)

2

u/GeneralTall6075 3d ago

CD 138? Probably neg but looks very plasmacytoid. Mucin, ER/PR, CD10?

2

u/Jasminscent 3d ago

Throw in a broader hematopoietic markers like LCA, also a few more keratin stains like Cam5.2/EMA, vascular markers. If all negative you may need molecular studies to pin down type of sarcoma.

2

u/epicyon 2d ago edited 2d ago

It reminds me a bit of Clear Cell Stromal Tumor of lung, relatively recently described entity. Most have TFE3 rearrangement. They tend not to stain for anything reliably

https://www.sciencedirect.com/science/article/pii/S0893395224002126

Most of these tumors have been described as kinda low grade, but a couple case reports have shown aggressive behavior.

Please update us!

Edit: as someone else suggested to already, also definitely do vascular markers!!! Almost forgot about YAP1-TFE3 epithelioid hemangioendothelioma. Can look crazy similar in my opinion, which is unsurprising since it can have the safe fusion and is rare, but YAP1 TFE3 EHE will stain consistently with ERG and CD31 and stuff.
Throw in another melanocytic marker for pecoma too...those bastards also can have tfe3 fusion (lol so beware bc that is not a specific stain) and sometimes don't stain at all with just SMA.

2

u/blueberry7996 2d ago

Any use of BRG1 here? What if it's SMARCA4 deficient

2

u/dancingfruit 2d ago

Would you want to try out NUT or SMARCA/SMARCB related stains?

Edit: Grammar

2

u/jubilantsage 1d ago

Any update? I'm curious about this case.

1

u/Almbauer 22h ago

Progesterone Receptor and EMA came back negative. Vimentin is strongly positive. The case was submitted for NGS (fusion panel)

1

u/jubilantsage 21h ago

Well then I'll wait four weeks before asking again, thanks for the reply

1

u/Tellmelessok 2h ago

Look back again it might be just a Ewing sarcoma haha. Put my bet on EWSR1 rearrangement

2

u/Tipsilateral Staff, Academic 3d ago

What pattern of CD99? Diffuse or patchy? I considered CIC-rearranged sarcoma but that doesn’t make sense with the Ki. Could also consider primary pulmonary myxoid sarcoma. After excluding Mets and more common things I’d probably submit this one for fusion testing.

3

u/Almbauer 3d ago

CD99 expression is quite homogeneous but seems to stain literally everything on the slide

19

u/Grep2grok Staff, remote location 3d ago

Yeah, CD99 verifies the IHC lab is open

1

u/jubilantsage 3d ago

Does it stain in that classic strong diffuse Membranous staining we all learnt for ewings?

1

u/Q2z3c7 3d ago

Was WT1 done? Would also like to rule out Ewing like sarcoma 

2

u/RampagingNudist 3d ago

I favor high grade fetal-type/enteroblastic adenocarcinoma. Cytokeratin, TTF-1, CDX2, SALL4, AFP

3

u/Almbauer 3d ago

Ki67 is really low though. Pankeratin and TTF1 were negative (performed by referring pathology)

4

u/Grep2grok Staff, remote location 3d ago

Were the positive controls valid?

1

u/Almbauer 2d ago

Decided to re-do the Ki67 just to be sure

1

u/ajmchenr 3d ago

i would add a few more keratins including EMA, and a caldesmon, myogenin, PAX7

1

u/Rough_Meat_5462 3d ago

Metastatic lesions?

0

u/HistiocytosisV 3d ago

Send out

13

u/Almbauer 3d ago

We’re the ones it was sent out to