Case 140

A 77 year old female with history of breast cancer and radiation therapy now presented with a chest wall mass.

1.The tumor is negative keratin, EMA, Melan-A, SMA, CK8/18, ERG, Desmin, STAT6, ALK, and caldesmon; partially positive for CD34, S100, PRAME and CD163. What's the basic diagnostic category?

A: Sarcoma

B: Undifferentiated carcinoma

C: Spindle cell neoplasm

D: Spindle cell melanoma

Answer

This is a challenging case and the best interpretation without molecular findings is spindle cell neoplasm, favor high grade sarcoma.

Immunohistochemical stains show tumor cells are partially positive for p63, focally positive for CD34, SMA, and desmin, and rare cells show ALK(D5F3) expression. The cells of interest are negative for pankeratin , EMA, CK5/6, p40, SOX10, MUC4, CD31, ERG, c-myc, and nuclear beta catenin. H3K27 me3 is partially retained.

Overall, the findings are of a spindle cell neoplasm with overall features favoring an high grade sarcoma. The differential diagnosis includes post-radiation undifferentiated sarcoma, DFSP with fibrosarcomatous transformation (although the outside report noted a negative COL1A1 gene rearrangement by FISH), and much less likely, metaplastic recurrence of invasive ductal carcinoma.

Case credit: UCSD Pathology

Author: Wangpan Jackson Shi, MD