Neuroendocrine and squamous cell phenotypes of NUT carcinoma are potential diagnostic pitfalls that discriminating it from mimickers, such as small cell and squamous cell carcinoma

Table 3 Immunohistochemical profiles of NUT carcinoma, basaloid squamous cell carcinoma, and small cell carcinoma

Case	NUT	CGA	SYN	CD56	TTF-1	P40	CK5/6	INSM1	ASCL1	BCL2	ProGRP	Ki-67	Abrupt keratinization	NUT split FISH	Fusion variant
NUT carcinoma (n = 8)
1	+	-	+ ^a	-^a	-	+ ^a	-	w +	-	-	-	NE	-	NE	NE
2	+	-	-	-	-	-	-	w +	-	w +	-	90	-	positive	NE
3	+	-	-	-	-	w +	w +	w +	-	-	-	80	-	positive	NE
4	+	-	w +	-	-	-	-	w +	-	+	-	50	-	positive	BRD4-NUT
5	+	-	-	-	-	+	+	w +	-	-	-	80	+	positive	NE
6	+ ^a	-	-	-	NE	NE	+ ^a	NE	NE	NE	NE	NE	+	positive	NE
7	+ ^a	NE	NE	NE	NE	+ ^a	NE	NE	NE	NE	NE	NE	-	NE	NE
8	+	-	-	-	-	+	+	w +	-	w +	-	70	+	positive	BRD4-NUT
Basaloid squamous cell carcinoma (n = 8)
1	-	-	-	-	-	+	+	-	-	+	NE	10
2	-	-	-	-	-	+	+	-	-	+	NE	20
3	-	-	-	-	-	+	+	-	-	+	NE	30
4	-	-	-	-	-	+	+	-	-	+	NE	10
5	-	-	-	-	-	+	+	-	-	+	NE	90
6	-	-	-	w +	-	w +	+	-	-	+	NE	60
7	-	-	-	+	-	+	+	-	-	+	NE	70
8	-	-	-	-	-	+	+	w +	-	+	NE	80
Small cell carcinoma (n = 13)
1	-	+	+	+	+	-	-	+	+	+	-	90
2	-	w +	+	+	+	-	-	+	+	+	+	90
3	-	w +	+	+	+	w +	-	+	w +	w +	-	85
4	-	-	+	+	+	-	-	+	w +	+	+	90
5	-	-	+	+	+	-	-	+	-	+	-	95
6	-	w +	+	+	+	-	-	+	+	+	w +	70
7	-	w +	+	+	+	-	-	+	+	+	+	95
8	-	+	+	+	+	-	-	+	+	+	w +	95
9	-	w +	+	+	+	-	-	+	w +	+	w +	90
10	-	-	w +	+	+	-	-	+	+	+	-	95
11	-	-	-	-	-	-	-	w +	-	+	-	95
12	-	w +	+	+	+	-	-	+	+	+	w +	80
13	-	+	+	+	+	-	-	+	+	+	-	100

CGA Chromogranin A, SYN Synaptophysin, NE Not examined
^astained slides were not available. positive cells; 1%–10% (-), more than 10% ( +) positive ( +): H-score was ≥ 100, weakly positive (w +) when the H-score was between 5 and 100 and negative when the H-score was < 5

ISSN: 1746-1596