Table 2.

Immunohistochemical profile of neuroendocrine tumors.

IHC	Typical carcinoid	Atypical carcinoid	Primary lung small cell ca.	Metastatic small cell ca.
CD56	+	+	+	+
Synaptophysin	+	+	+/−	+/−
Chromogranin	+	+	−/+	−/+
TTF-1	−/+	−/+	Usually +	Usually −
Ki-67	0–5%	5–15%	>20% (typically >60%)	>20% (typically >60%)