Table 2.

The isolation and detection of tumor cytosol, body fluid and exosome miRNAs.

Classification	Tumor cytosol miRNAs	Body fluid miRNAs	Exosome miRNAs
Sources	Fresh tumor tissues or FFPE tissues	Whole blood, serum, plasma, urine, CSF, sputum, saliva, or BAL
Special sample process for miRNA isolation	None	Need to avoid protein contamination	Need to isolate exosomes
Complexity of isolation	+	++	+++
Detection	qRT-PCR, Northern blot, NGS, microarray
Invasiveness	Yes	None	None
Main function	Diagnosis, prognosis and therapy	Early diagnosis and prognosis	Early diagnosis, prognosis and drug transportation

FFPE, formalin-fixed paraffin embedded; CSF, cerebrospinal fluid; BAL, bronchoalveolar lavage; NGS, next generation sequence.