I do think that this is a tough case...You just have to think about it.

The diagnosis is: adenomatoid tumor (cellular)

The differential diagnoses that were mentioned are all very appropriate.

The helpful features are:

1. usually small, well circumscribed nodule

2. paratesticular rather than intra-testicular location (can happen)

3. cells with vacuoles

4. no cytologic atypia or mitosis

5. can have dense stroma, smooth muscle, lymhphoid infiltrate

6. of course calretinin is helpful

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Please share your experience and interesting case!

 支持细胞肿瘤 is a good guess! I hope you will agree that morphogy is very unique with haylinzed material around epithelial-like cord or trabeculae of cells. Differential diagnoses might be include:

1. Leydig cell tumor

2. Metastatic carcinoma

3. Malignant mesothelioma

4. Adenomatoid tumor

5. Any others?

what's your top choices and what stains (if necessary) do you want the most?