Frozen section diagnosis and differential diagnoses?

Answer will be posted after Chinese New Year.

Happy New Year!

• It is metastic melanoma (hope Dr. Ma can comment again).
• S100 and HMB 45 were positive and cytokeratin was negative.
• On frozen, we will need to keep a wide differential (such as Dr. Jin's list).
• Look for features that will favor non-neoplastic (granuloma), benign vs. malignant, primary vs. metastatic.
• On this case, I thought the touch prep cytology is very helpful (epithelioid spindle cells with nucleoli).

 谢谢Dr.shen！

IHC怎样呢?

Malignant for sure.

Malignant melanoma (metastatic much more likely than primary) is my first choice. Large cell carcinoma remains likely and needs to be ruled out. Dendritic cell sarcoma is much less likely. I cannot exclude a rare metastatic thymic carcinoma.

Confirm with at least two of melanocytic markers (S100, Melan A, HMB45, MITF) and AE1 first. If AE1 is positive and melanocytic markers are negative, add TTF-1, CD5 and CD117. If only S100 is positive and the other melanocytic markers and AE1 are negative, add CD68 and two of follicular dendritic cell markers (CD21, CD23, CD35).

This is not paraganglioma, meningioma, thymoma or carcinoid tumor.

Benign vs malignant?

Primary vs metastatic?

What shoulbe be your initial IHC panel?

类癌?

Thanks for the discussion.

This case may illustrate the importance of cytologic evaluation.

Here are a few permanent H&E photomicrographs.

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描述：图1

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描述：图3