Case 33

A young female was found to have a cervical lesion and the biopsy is shown as follows:

1.What's the morphology impression and what stains you would like to order?

IHC

• p16
• Pan-keratin
• PAX-8
• ER, PR

See All Options

2. The tumors were diffusely positive for p16, negative for all the marker above, except for small amount of claudin 4. IN1 and BRG1 were retained. What's your favored diagnosis?

   
   

A. HPV-related endocervical adenocarcinoma

B. HPV-related small cell carcinoma

C. Lymphoma

D. poorly differentiated neoplasm/carcinoma

E. Undifferentiated carcinoma

Answer to question 1 and 2

The impression and answer of poorly differentiated neoplasm or carcinoma are both reasonable. And this is a case of undifferentiated carcinoma likely from endometrial carcinoma based on two testings; HPV in situ hybridization was negative and NGS showed mutation in PTEN, CTNNB1, ARID1A. These three are commonly detected mutations in endometrioid type of endometrial carcinoma. In undifferentiated carcinoma, p16 positivity can be a pitfall that 14/28 (50%) can be positive.

Reference: Saad RS, Mashhour M, Noftech-Mozes S, Ismiil N, Dubé V, Ghorab Z, Faragalla H, Khalifa MA. P16INK4a expression in undifferentiated carcinoma of the uterus does not exclude its endometrial origin. Int J Gynecol Pathol. 2012 Jan;31(1):57-65. doi: 10.1097/PGP.0b013e318223118a. PMID: 22123724.

Case credit: UCSD Pathology

Author: Wangpan Jackson Shi, MD