Table 1.

Difference between isolated tumour cells and micrometastasis. Adapted from: Hermanek P, Hutter RVP, Sobin LH, Wittekind C. Classification of isolated tumour cells and micrometastasis. Cancer 1999; 86: 2668–2673

	Isolated tumour cells	Micrometastasis
Size	Single tumour cells or small clusters ≤ 0.2 mm or < 200 cellsa	≤ 0.2 cm in greatest dimension
Contact with vessel or lymphatic wall	No	Yes
Invasion and penetration of vessel or lymphatic wall	No	Yes
Extravascular stromal reaction	No	Usually yes
Extravascular tumour cell proliferation	No	Yes

^aUpdated from AJCC/UICC TNM cancer staging 8th edition