POWER OF ATTORNEY
        The undersigned hereby constitutes and appoints each of Maneesh 
Arora, Mark Busch, June Fontana and Kyle Stacey, signing singly, as the 
undersigned's true and lawful attorney-in-fact to:
        (1)        execute for and on behalf of the undersigned, in the 
undersigned's capacity as an officer and/or director of Exact Sciences 
Corporation (the "Company"), Forms 3, 4 and 5 in accordance with Section 
16(a) of the Securities Exchange Act of 1934 and the rules thereunder 
(the "Exchange Act"), as well as the Form ID to obtain and/or renew EDGAR 
codes for use in connection with the filing of Forms 3, 4 and 5 and any 
other related documentation;
        (2)        do and perform any and all acts for and on behalf of the 
undersigned which may be necessary or desirable to complete and execute 
any such Forms 3, 4 or 5, Form ID or other related documentation, 
complete and execute any amendment or amendments thereto, and timely file 
such forms or documentation with the United States Securities and 
Exchange Commission and any stock exchange or similar authority;
        (3)        take any other action of any type whatsoever in connection 
with the foregoing which, in the opinion of such attorney-in-fact, may be 
of benefit to, in the best interest of, or legally required by, the 
undersigned, it being understood that the documents executed by such 
attorney-in-fact on behalf of the undersigned pursuant to this Power of 
Attorney shall be in such form and shall contain such terms and 
conditions as such attorney-in-fact may approve in such attorney-in-
fact's discretion; and 
        (4)        in connection with the preparation and filing of Forms 3, 4 
and 5, seek or obtain, as the undersigned's attorney-in-fact and on the 
undersigned's behalf, information regarding transactions in the Company's 
securities from any third party, including brokers, employee benefit plan 
administrators and trustees, and the undersigned hereby authorizes any 
such person to release any such information to such attorney-in-fact and 
approves and ratifies any such release of information. 
        The undersigned hereby grants to each such attorney-in-fact full 
power and authority to do and perform any and every act and thing 
whatsoever requisite, necessary, or proper to be done in connection with 
the exercise of any of the rights and powers herein granted, as fully to 
all intents and purposes as the undersigned might or could do if 
personally present, with full power of substitution or revocation, herby 
ratifying and confirming all that such attorney-in-fact, or such 
attorney-in-fact's substitute or substitutes, shall lawfully do or cause 
to be done by virtue of this Power of Attorney and the rights and powers 
herein granted.  The undersigned acknowledges that the foregoing 
attorneys-in-fact, in serving in such capacity at the request of the 
undersigned, are not assuming, nor is the Company assuming, any of the 
undersigned's responsibilities to comply with Section 16 of the Exchange 
Act.
        This Power of Attorney shall remain in full force and effect until 
the undersigned is no longer required to file Forms 3, 4, and 5 with 
respect to the undersigned's holdings of and transactions in securities 
issued by the Company, unless earlier revoked by the undersigned in a 
signed writing delivered to the foregoing attorneys-in-fact.  
        This Power of Attorney does not relieve the undersigned from 
responsibility for compliance with the undersigned's obligations under 
the Exchange Act, including, without limitation, the reporting 
requirements under Section 16 of the Exchange Act.  Additionally, 
although pursuant to this Power of Attorney the Company will use 
commercially reasonable
best efforts to timely and accurately file Section 16 reports on behalf 
of the undersigned, the Company does not represent or warrant that it 
will be able to in all cases timely and accurately file Section 16 
reports on behalf of the undersigned due to various factors, including, 
but not limited to, the shorter deadlines mandated by the Sarbanes-Oxley 
Act of 2002, possible time zone differences between the Company and the 
undersigned and the Company's need to rely on other parties for 
information, including the undersigned and brokers of the undersigned.
        IN WITNESS WHEREOF, the undersigned has caused this Power of 
Attorney to be executed as of this 27th day of August, 2013.

                                                /s/ William J. Megan        
        
                                                William J. Megan