Table 10.

Differential diagnosis of small-cell urethral NEC [124,125,128].

Differential Diagnosis	Characteristic of Urethral NEN That Helps in Distinguishment
Lymphoma	Positive immunohistochemistry with LCA antigen
Transitional cell carcinoma	Positive p63 and CD44v6 (80% specific)
Carcinoid tumor	Abundant eosinophilic cytoplasm and regular nuclei
Primary neuroectodermal tumor	Larger cell bodies with spread out cytoplasm in dendritic processes
Metastatic small-cell carcinoma	Positive TTF-1 and presence of primary site on chest CT
Merkel cell carcinoma	Penile or scrotal skin involvement and presence of punctate paranuclear cytokeratin staining; positive CK20