Table 1.

FCM criteria for BCC and their subtypes.²⁹

FCM criteria and $p$ valuea for subtyping BCCs	sBCC	nBCC	iBCC	Definition of FCM criteria
Presence of fluorescence ($<0.01$)	$3+$	$3+$	$3+$	Nucleated cells stained with acridine orange
Well demarcated ($<0.01$)	$1+$	$3+$	$2+$	Separation of tumor border from surrounding stroma
Nuclear crowding (0.60)	$1+$	$3+$	$3+$	Nuclear density higher than surrounding epidermis and adnexal structures
Nuclear pleomorphism (0.80)	$3+$	$3+$	$3+$	Deviation from normal round-oval nuclear outline of normal keratinocytes
Increased N/C ratio	$3+$	$3+$	$3+$	Elongated heterogeneous fluorescent (spots) nuclei with poor/absent cytoplasm
Palisading	$3+$	$3+$	$3+$	Peripheral polarized aligned fluorescent ellipses: outermost row of basal cells
Clefting ($<0.01$)	$3+$	$3+$	$2+$	Black fluorescence-free half-moon attached to the tumor mass
Tumor stroma				Densely nucleated dermis reminiscent of a “starry sky”
Absent ($<0.05$)	$2+$	$1+$	$1+$
$<50\%$	$2+/3+$	$1+$	$2+$
$>50\%$	$1+$	$3+$	$3+$

Note: iBCC, infiltrating BCC; nBCC, nodular BCC; sBCC, superficial BCC; N/C ratio, nuclear-to-cytoplasmic ratio. The numbers $1+$, $2+$, $3+$ indicate the relative frequency with which the FCM features were present in a particular subtype of BCC.

^aStatistically significant differences between BCC subtypes in demarcation, nuclear crowding, clefting, and stroma are shown.