Shares of Personalis (NASDAQ: PSNL) experienced a sharp 17.30% decline in after-hours trading on Tuesday following the release of its third-quarter 2025 financial results. While the company managed to beat revenue expectations for Q3, its weaker-than-anticipated fourth-quarter guidance appears to have spooked investors, leading to the significant stock price drop.

Personalis reported Q3 revenue of $14.495 million, surpassing the analyst consensus estimate of $13.3 million. However, this figure represents a substantial 44% year-over-year decline. The company's net loss for the quarter stood at $21.652 million, or $0.24 per share, which was better than the expected loss of $0.28 per share. Despite these mixed results, the market's focus seems to be on the company's future outlook.

The primary catalyst for the stock's plunge appears to be Personalis's disappointing Q4 guidance. The company forecasts Q4 revenue between $15.7 million and $20.7 million, well below the consensus estimate of $21.8 million. Additionally, Personalis revised its full-year 2025 revenue projection to a range of $68.0 million to $73.0 million, further fueling investor concerns about the company's near-term financial performance. On a positive note, Personalis reported a 364% year-over-year growth in clinical test volume, driven by increased adoption of its NeXT Personal platform. However, this growth was not enough to offset the negative sentiment surrounding the company's financial outlook.