Table 1.

Differential diagnosis to Intestinal T cell lymphomas

	NK-cell enteropathy	Indolent T cell LPD of the GI tract	EATL	MEITL
Epidemiology	Unknown	Unknown	Northern Europe	Asian, Hispanic
Associations	Unknown	Unknown	Celiac, HLA-DQ2, HLA-DQ8	Unknown
Location	Stomach, small intestine, colon	Small intestine, colon, others	Small intestine	Small intestine
Histology	Medium to large in size, with mild cytological atypia. Destruction of adjacent glands may be present at advanced stages Epitheliotropism is usually absent.	Small and monotonous lymphocytes, with none to mild cytological atypia. Non-destructive. Occasional epitheliotropism.	Pleomorphic. Medium to large with cytological atypia. Epitheliotropism is usually present. Angiodestruction may be present.	Monomorphic medium cells. Epitheliotropism usually present.
Phenotype	cCD3 + a CD8- CD5- CD7 + CD4- CD56 + TIA1 + EBER(ish)- Granzyme B +  Low Ki-67(< 25%)	CD2 + CD3 + CD5 ± CD7 ± CD8 +  > CD4 + c CD56- TIA1-/ +  Granzyme B- EBER(ish) - Low Ki-67 (< 10%)	CD3 + CD4- CD5- CD7 + CD8-/ + d CD56- CD103 + CD30 ±  TIA-1 + , Granzyme B +  High Ki-67 (> 50%)	CD3 + CD5- CD8 +  > CD4 + CD56 + b CD30- CD103 + TIA1 + Granzyme B + EBER(ish)- High Ki-67 (> 50%). MATK + #
TCR expression	Negative	Alpha beta (αβ)	Alpha beta (αβ) > gamma delta (ɣδ)	Gamma delta (ɣδ) > Alpha beta (αβ)
Molecular	TCR polyclonal	STAT3-JAK2 fusion	STAT5B, JAK3, GNAI2 Gains of 1q and 5q	SETD2, STAT5B, JAK3, GNAI2 Gains of MYC

^a Concurrent flow cytometry analysis demonstrates that CD3 expression is cytoplasmic

^b Majority of tumors (~ 80%) are CD8 + , a small subset of cases (9–18%) can be negative for CD56

^c Majority of the cases are CD8 + (~ 80%), a minority of the cases are either CD4 + or double CD4/CD8 negative in similar proportions

^d Approximately 30% of the cases are CD8 + , majority of the cases are CD4-/CD8-. ^#MATK/Lsk nuclear expression is detected in majority of MEITL cases and in NK/T cell lymphomas, whereas EATL cases only feature cytoplasmic staining