THe minimum voltage it can sense is:
(ADC Reference Voltage)/(2^n) where n is the number of bits the ADC has.
So at 5V, the minimum a 10-bit ADC can detect is 5/4096 = 4.88 mV.
So no. Also, remember the thermocouple can output NEGATIVE voltages at certain temperatures so if it's measuring cold your PIC won't work either (and may be damaged). You need a very large gain, very quiet, differential amplifier that may need to be bipolar (depending on the temperature you are going to encounter).
See your other post. I explained it more there.