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Case History

75 years old female. MR image shows a 5.2 x 4.4 x 4.0 cm perianal mass. This is left perirectal mass biopsy:

What is the diagnosis?

  1.       Adenoid cystic carcinoma 
  2.       Benign cellular mixed tumor
  3.       Malignant mixed tumor
   HE 1   HE 2

Answer: A. Adenoid cystic carcinoma

 The neoplasm reveals mixed epithelial and myoepithelial components, without significant cytologic atypia, embedded in a chondromyxoid stroma. The epithelial component shows strong cytoplasmic positivity with cytokeratin (AE1/AE3), while the myoepithelial component is positive for S100 protein and p63 (with all appropriate controls). Salivary Duct Tumor Gene Fusion Analysis detected MYB-NFIB gene fusion, which supports this is an adenoid cystic carcinoma.

Case contributed by: Shoujun Chen, M.D., Ph.D., Breast/GYN Fellow