This is a photograph of a herring, a small, oily fish of the genus Clupea found in the shallow, temperate waters of the North Pacific and the North Atlantic, including the Baltic Sea.
Most people are familiar with the term "red herring". In the investment world, a red herring is associated with initial public offerings (IPOs). A red herring is a preliminary registration statement that must be filed with the SEC describing a new issue of stock and the prospects of the issuing company.
Outside the financial world, a red herring is an item or event that distracts the observer from what is truly important. The origin of the term is somewhat controversial but most associate it with hunting. When herrings are cured, they turn red and acquire a distinctive smell. Hunting dogs were taught to follow a trial by following the scent of a herring that was dragged along the ground. Red herrings may also have been used to confuse the hounds in order to prolong a fox hunt or to test their ability to stay with a scent.
Occasionally, we run across red herrings in medicine as well. In this case, a 35 year-old female presented to her physician with a mass behind the elbow. She was sent for an MRI:
(A) Coronal T1-weighted and (B) T2 fatsat images reveal a T2 hyperintense mass (red arrows) corresponding to a clinically palpable abnormality.
An axial T2 fatsat image confirms the mass (red arrows) under a skin marker placed by the technologist (yellow arrow):
(A) Axial precontrast T1 fatsat and (B) postcontrast T1 fatsat images obtained immediately after IV contrast administration reveal strong enhancement associated with the lesion, which has irregular margins:
The history obtained by the MRI technologist reported no history of recent trauma. Given this, a differential of various neoplastic entities was offered, and the patient was referred to an orthopedic oncologist.
Up to this point, the patient had proceeded at a breakneck pace through the medical system. At the orthopedic oncologist, things finally slowed down. The astute orthopedic oncologist obtained a careful history, which included a possible history of a bleeding disorder. After careful consideration, he opined that this was likely a hematoma, despite the strong enhancement seen on MRI.
Over the next several weeks, the mass decreased in size, and a follow-up scan eight weeks later confirmed resolution of the hematoma:
This case illustrates many things, not the least of which is the importance of an accurate clinical history. It is also a good example of how hematomas can rarely enhance, particularly along their periphery. Cases have been described of chronically expanding hematomas which enhance, simulating a neoplasm (Skel Rad 35:1432, 2006)
Although gadolinium enhancement is often associated with neoplasms, in some cases it can be a red herring, as this case illustrates.
Vic David MD