Table 1.

Major features in the differential diagnosis of SC

	SC	AciCC	Low-grade MEC
Architecture	Papillary, flat sheets, microcystic, or singly dispersed cells	Closely packed or overlapping acinar structures, microcystic on histology	Cystic
Background	Hemorrhagic with histiocytes, or sparsely mucinous. Intraluminal eosinophilic secretions on histology	None	Extracellular mucin may be abundant
Cytoplasm	Moderate amount of vacuolated eosinophilic cytoplasm	Granular basophilic cytoplasm	Mucinous, intermediate and squamoid and dense
Cytoplasmic contents	Mucin, rare signet ring-like cells, hyaline globules	Zymogen granules	Mucus-containing goblet cells
Nucleus	Round to oval nuclei with smooth nuclear contours, small or inconspicuous nucleoli, low mitotic activity	Round to oval nuclei with smooth nuclear contours, small or inconspicuous nucleoli, low mitotic activity	Round to oval nuclei with smooth nuclear contours, small or inconspicuous nucleoli, low mitotic activity
Immunophenotype	Positive for S100, SOX-10, vimentin, and mammaglobin; Negative for p63 and DOG-1	Positive for SOX-10, DOG-1 and NR4A3; Negative for p63 and mammaglobin	Positive for p63; Negative for S100
Molecular characteristics	ETV6-NTRK3	Recurrent translocations involving the upstream elements of NR4A3 at 9q31	CRTC1 (MECT1)-MAML2

AciCC: acinic cell carcinoma; MEC: mucoepidermoid carcinoma, PAS-D: periodic acid-Schiff with diastase; NR4A3: Nuclear receptor subfamily 4 group A member 3