Table 5.

Histologic findings and IHC profile of p40-negative lung squamous cell carcinoma

Case No.	Nature of specimen	p40	p63	Histologic grade	Squamoid morphology	Other IHC
2	Lung biopsy	1+ (in < 5%)	1+	Poorly differentiated	-	CK7+, TTF1–
3	Lung biopsy	0	0	Poorly differentiated	Focal intercellular bridging and keratinization	-
4	Lung biopsy	0	0	Poorly differentiated	Intercellular bridging and keratinization	-
9	Lung biopsy	0	2+ (in > 50%)	Poorly differentiated	Abundant eosinophilic cytoplasm	CK+, TTF1+ (focal)
21	Lung biopsy	0	2+ (in 5%–25%)	Poorly differentiated	Focal intercellular bridging and keratinization	TTF1–, p63+
22	Lung biopsy	0	0	Poorly differentiated	Abundant eosinophilic cytoplasm	TTF1–, CK5/6-
33	Lung biopsy	0	0	Poorly differentiated	Abundant eosinophilic cytoplasm	CK7+ (focal), p63+ (focal), TTF1–
34	Lung biopsy	1+ (in < 5%)	2+ (in 5%–25%)	Poorly differentiated	Focal intercellular bridging	CK7+, p63+, TTF1–

IHC, immunohistochemistry; CK, cytokeratin; TTF1, thyroid transcription factor 1.