Exact Sciences (EXAS 0.91%) released its results for the fourth quarter of 2020 after market close on Tuesday. Investors indicated their displeasure by trading the stock down.

For the period, the healthcare diagnostics specialist posted just over $466 million in revenue, which was nearly 58% higher on a year-over-year basis.

On a less encouraging note, it flipped to a net loss of almost $437 million ($2.79 per share) on the bottom line. However, this was heavily affected by a nearly $413 research and development charge the company booked due to the acquisition of cancer diagnostics developer Base Genomics. In Q4 2019, Exact Sciences' net income was almost $78 million.

Doctor writing on a patient's medical chart.

Image source: Getty Images.

On average, analysts were expecting $446 million on the top line, but a per-share net loss of only $0.22. Some net loss estimates might not have factored in such a heavy R&D charge from the Base Genomics deal.

Exact Sciences' revenue growth has been fueled by both its cancer diagnostics and its coronavirus testing products. As the pandemic (hopefully) subsides, the company is counting on the former category to drive growth.

"We are a leader in cancer diagnostics because of our people, scientific platform, and market-leading Cologuard and Oncotype tests," CEO Kevin Conroy said. "We aim to extend this leadership throughout the cancer continuum and bring additional tests to patients to help improve cancer outcomes."

Investors might not be buying Conroy's line. The stock was down by 4.4% in post-market trading, which compared unfavorably to the slight decline of the S&P 500 index during regular hours.