Case 4
- Wangpan Shi
- Jan 6
- 2 min read
Updated: Jan 23
A 70 year old male with a large anterior mediastinal mass.
1.What's the morphology impression?
A: Germ cell tumor, favor yolk sac tumor
B: Ewing sarcoma
C: CIC-DUX sarcoma
D: Sarcoma with BCOR rearrangements
E: Rhabdomyosarcoma
F: Melanoma
G: Poorly differentiated carcinoma
H: MPNST
2.What's your panel of work up?
IHC
Pan-keratin
WT1
CD99
SALL4
You can vote for more than one answer.
Answer
There is no right answer for the panel. A initial panel of Pan-keratin, LCA, S100, Myogenin, SALL4, CD99 is appropriate.
A limited panel was performed. The lesional cells to be diffusely positive for myogenin, with patchy expression of desmin and glypican 3, retained h3k27me expression, and no significant expression of SALL4, keratin, SOX10 and S100. CD99, BCOR, WT1 are all negative. You are about to sign out the case while waiting for molecular test. What's the favored diagnosis at this point?
A: Germ cell tumor, favor yolk sac tumor
B: Ewing sarcoma
C: CIC-rearranged sarcoma
D: Sarcoma with BCOR rearrangements
E: Rhabdomyosarcoma
F: Melanoma
G: Poorly differentiated carcinoma
H: MPNST
Answer
The correct answer at this point is E or high grade malignancy with rhabdomyosarcomatous differentiation given the positivity of myogenin and morphology of rhabdomyoblast in the last image. SALL4 negative will be unusual for yolk sac tumor. An perfectly retained H3K27me expression exclude MPNST. Negative for CD99, BCOR, WT1 excludes tumors including Ewing sarcoma, sarcoma with BCOR rearrangement, and CIC-rearranged sarcoma. Keratin negative exclude poorly differentiated carcinoma.
The case was sent for sarcoma fusion panel and a PAX3-FOXO1 fusion was detected. What's the following statement is true?
A: PAX3-FOXO1 can be seen in embryonal rhabdomyosarcoma.
B: The presence of small round tumor cells and differentiating rhabdomyoblasts in this case represent embryonal rhabodomysarcoma.
C: PAX7-FOXO1 in alveolar rhabdomyosarcoma has worse prognosis
D: Given the PAX3-FOXO1 fusion, this case is alveolar rhabdomyosarcoma
Answer
The correct answer is D. PAX3-FOXO1 in alveolar rhabdomyosarcoma has an inferior prognosis compared to PAX7-FOXO1. Although the presence of differentiating rhabdomyoblasts in this case may suggestive of an embryonal rhabodomysarcoma, the finding of PAX3-FOXO1 is diagnostic for ARMS. In sporadic cases of ERMS, whole chromosome gains are present, including polysomy 8 and extra copies of chromosomes 2, 11, 12, 13 or 20. ERMSs of the uterus occur in DICER1, and rhabdomyosarcomas with unclassified histology are observed in Li-Fraumeni syndrome (TP53 mutations).
References:
Case credit: UCSD Pathology
Author: Wangpan Shi
Comments