Tuesday started off well for AngioDynamics (ANGO -10.18%), maker of such medical devices as the NanoKnife tool for "electrocuting" cancer, as well as multiple devices for treating peripheral vascular disease. In the morning, AngioDynamics reported stronger-than-expected Q4 2025 sales and earnings, with sales of $80.2 million and an adjusted loss of $0.03 per share (instead of the $0.12-per-share forecast).

By the end of the day, however, the rally fell completely apart. AngioDynamics ended up closing down almost 10% for the day. So what went wrong?

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AngioDynamics' Q4 earnings

Q4 sales grew 13% year over year, although gross profit margins on those sales declined by 160 basis points, to 52.7%. Adjusted earnings still ended up better than expected, and AngioDynamics cut its loss as calculated according to generally accepted accounting principles (GAAP) by more than half, from $0.33 per share a year ago to just $0.15 per share this time around.

Still, a loss is a loss. That's part of the reason investors probably weren't 100% thrilled with this report. For the full-year fiscal 2025, moreover, AngioDynamics lost $0.83 per share according to GAAP, and its sales grew only 8.1%.

Is AngioDynamics stock a sell?

A second reason is guidance. AngioDynamics told investors it expects fiscal 2026 sales to range from $305 million to $310 million, which is ahead of Wall Street forecasts -- so far, so good. Problem is, management then proceeded to warn its losses for the year will range from $0.25 to $0.35 per share, adjusted for one-time items.

That's more than the $0.23 per-share loss Wall Street was forecasting -- and AngioDynamics still hasn't told us how much it will really end up losing under GAAP. Until we know that, the stock probably remains a sell.