Matching oscilloscope impedance to detector
As mentioned in one of the comments if the cable is short there will be very little effect at 10MHz - short means that the cable is much less than one wavelength.  For example the delay through 1 meter of cable will be ~5ns, the reflection will get back to the amplifier in another ins giving a 10s round trip.  This is 10% of the 10MHz upper limit that you have.

The gain of the amplifier will be double the calibrated value (i.e. a 20dB amplifier will have a voltage gain of 26dB in this condition).

The rolloff of 16pF and 50Ohms will be 3dB @ 200MHz so nothing to worry about.

If the scope does not have a 50 ohm input selection and you want to terminate the cable correctly I would use a BNC T connector plugged into the scope with a 50 Ohm terminator in one of the ports and the input signal into the other.