October 15, 2012 Pecora and Company

Exhibit 10.55

October 15, 2012

Xxxxxx and Company

000 Xxxxx Xxxxxx - Xxxxx 000

Xxxxxxxxxx, Xxx Xxxxxx 00000

Attention: Xx. Xxxxxx Xxxxxx

Re: Amended and Restated Credit Agreement with Cancer Genetics, Inc.

Dear Xx. Xxxxxx:

This letter agreement will memorialize your agreement to cancel the Warrant #120, #126, and #130 issued to Xxxxxx and Company in connection with its loan to the Company pursuant to the Amended and Restated Credit Agreement (“Credit Agreement”) by and among between XXXX XXXXXXXXX (“Xxxxxxxxx”), XXXXXX AND COMPANY (“Xxxxxx”) and NNJCA CAPITAL, LLC (“NNJCA”, and with Pappajohn and Xxxxxx, collectively the “Lender”), and CANCER GENETICS, INC., a Delaware corporation (the “Company”), dated of February 13, 2012 and to amend the promissory note (the “Note”) to increase the pre-payment penalty. The Note is hereby amended to provide that the pre-penalty payment shall be increased by $32,000. You agree that, notwithstanding the terms of the Credit Agreement, Xxxxxx is not entitled to any warrants in connection with its loan to the Company and that any and all warrants issued to Xxxxxx pursuant to the Credit Agreement are hereby cancelled.

Very truly yours,

/s/ Panna X. Xxxxxx

Panna X. Xxxxxx

President and CEO

Agreed to and Accepted by:

/s/ Xxxxxx Xxxxxx

Xxxxxx and Company