The disclosure relates to a heat exchanger comprising a central body (10) with a first set of channels (A ij ) and a second set of channels (B ij ) extending along a main direction (L) through the central body (10), wherein, in the central body (10), in any cross-section across the main direction (L), the channels (A ij , B ij ) of the first and second sets form a checkered pattern in said cross-sections, wherein the heat exchanger (1) further comprises two inner transition portions (20), wherein, in respective inner transition portion (20), among the rows (X 1X , X 2X , X 3X , X 4X , X 5X , X 6X , X 7X , X 8X ) extending along a first direction (T 1 ), are every second, counted along a second direction (T 2 ), row (X 2X , X 4X , X 6X , X 8X ) provided with channels (X 2X , X 4X , X 6X , X 8X ) being along the main direction (L) increasingly shifted in position in a first direction (T 1 ) relative to the other channels (X 1X , X 3X , X 5X , X 7X ) such that the checkered pattern of channels is transformed into a line pattern.