CASE IS OPEN FOR DISCUSSION!  
 
41yrs old male with generalized lymphadenopathy and splenomegaly.  
Biopsy core from left suprclavicular LN with repeated excisional biopsy.  
PET-CT: no definite PRIMARY. High active LNs supra and sub-diaphragmatic with conglomeration. SUSPITIOUS nidus in right kidney (tumor spread vs reactive/urine stasis?). Urolgists are sure, that not kidney primary.  
 
FULL IH (core biopsy): PanCK+; Pax8+; p53+ (probably mutated); Vimentin+; TLE1+; BerEp4/EMA(-); CD35+/-; CKHMW/p63/p40/CK5(-); CK7/CK20(-); CAIX/RCC/CD10/Synaptophysin/Chromogranin A(-); TTF1/CDX2/SALL4(-); CD117/CD5/Asm Actin/Desmin/Myogenin/STAT6(-); Ki67 prolif. index up to 30%.  
ALK1 r-jos nėra (0); TFE3(-);  
 
REPEATED IH (excisional biopsy): the same. ADDITIONAL: Fascin +/- faint; EGFR+ (membranous) weak focal;  
 
MOLECS: FOUNDATION ONE:  
FOUNDATION ONE short summary:  
NF2 E204*  
ATR RAB7A-ATR rearrangement  
CDKN2A/B p14ARF rearrangement exon 1  
Microsatellite status - MS-Stable  
Tumor Mutational Burden - 2 Muts/Mb  
UNKNOWN SIGNIFICANCE.  
FLT1 S733del  
RET Y791F  
E-MICROSCOPY: attched picture (low quality).  
 
PROPOSAL 1: Malignant epithelioid tumor, probably fibrous dendritic cell tumor/sarcoma (aka Cytokeratin-positive interstitial cell neoplasm) if any other carcinomas were excluded (kidney? other?).  
PROPOSAL 2: Due to biopsied renal tumor (the same picture and IH, not included): just RCC NOS mts to lymphnode.  
 
ThankYouforContinousHelp

Enguerrand20 2021-09-17 11:33	It looks like an epithelioid sarcoma. We don't recognise a kidney tumor and PAX8 may be positive in some sarcoma such as SFT but here STAT6 is not expressed, Synocial Sarcoma (here TEL1 is positive). We would add some IH: SS18 for a SS, INI1 for an epithelioid sarcoma, CD68, S100, CD21, CD23 for a FDC sarcoma. Rodrigo and Aurore
ugnius 2021-09-17 12:05	Hi and thanx. ALL KINDS of FDC markers are negative (except some noise from CD35). Another thoughts are good, but:   - we have no primary mass and lymh node mts only;   - CD34(-) and TLE1 is heterogenous.   Anyway NGS will show all possible mutations mentioned. If I remember correctly INI1 was retained.   Be back and thank You one more time.
tzankov 2021-09-20 21:08	PAX8 and PanCK as well as the metastatic spread are rather carcinoma-like. I do not expect histiocytic sarcoma to be compatible with life with such a broad spread. Staining for SMARCA4 and SMARCB1/INI1 are good ideas. CK19, CA15-3, CA19-9 might be useful too. Is there a tumor in the spleen? Why are urologists sure that this is not a kidney tumor? Has someone looked at the testicles of the patient?
ugnius 2021-09-28 14:30	Please find E-microscopy from paraffin (low quality). Additional core from kidney projection was done (to be contd). NGS will be publish there soon.
ugnius 2021-10-09 14:38	FOUNDATION ONE short summary:   NF2 E204*   ATR RAB7A-ATR rearrangement   CDKN2A/B p14ARF rearrangement exon 1   Microsatellite status - MS-Stable   Tumor Mutational Burden - 2 Muts/Mb   UNKNOWN SIGNIFICANCE.   FLT1 S733del   RET Y791F
ugnius 2021-10-09 14:40	Kidney biopsy showed the same picture.
tzankov 2021-10-10 16:35	Sarcomatoid RCC would be poribably the best fitting basket, as I prvioudsly said - PAX8 and CK+ as well as the metastatic spread fit best with RCC. I keep my fingres crossed for the patient.
Enguerrand20 2021-10-12 11:35	Metastatic sarcomatoïd RCC is unfotunately also our first diagnosis.
ugnius 2021-10-18 09:37	Thanx for help and ideas.
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