Some types of acute leukemia are composed of only blasts (no differentiating neutrophils, no monocytic precursors, just a sea of blasts). In those cases, look for Auer rods. A blast with an Auer rod can only be a myeloblast! It cannot be a lymphoblast, or a monoblast, or any other kind of blast. So if you see blasts with Auer rods, you know it is some type of acute myeloid leukemia. Remember, though, that the converse is not true: just because you don’t see Auer rods, that does not mean that the blast is not a myeloblast. Some myeloblasts have Auer rods, and some don’t. So if you see Auer rods, it is an AML. If you don’t, it still could be an AML.
There are some terms in pathology that are used interchangeably – but shouldn’t be. “Reticulin” and “collagen” are two of these terms. Reticulin fibers are the same thing as type III collagen. They are fine, delicate fibers made by fibroblasts. There are other types of collagen (types I, II, and IV are the main ones, but there are more) that have different appearances and are found in different places. Type I collagen is the main component of bone, type II is the main component of cartilage, and type IV is the main component of basement membranes.
Polycythemia vera (PV) is a chronic myeloproliferative disorder in which the red cells are the predominant lineage. Here are some typical student questions along with my answers.
Q.Are the erythrocytes in PV normal?
A. No, they aren’t considered normal because they come from a malignant clone of erythroblasts. But they do carry oxygen, and they do act and look like benign RBCs. They’re just the end stage of a malignant erythroblast’s development.
Q. How come the oxygen saturation is normal in PV?
A. You use the oxygen saturation to tell apart primary polycythemia (polycythemia vera) from secondary polycythemia. In secondary polycythemia, the oxygen saturation is usually low (that’s why the patient is making so many red cells – he or she needs to create more oxygen carrying capacity! Maybe the patient lives way up in the mountains or something.). In contrast, the oxygen saturation is normal in polycythemia vera, because the malignant RBCs are simply carrying the oxygen that happens to be around (and they carry it the same way benign RBCs do), and unless the person with polycythemia vera happens to live way up in the mountains and smoke (pretty unlikely), the oxygen saturation in that person should be normal.
Q. Does the test for RBC mass necessarily tell you whether the red cells are benign?
A. The test for RBC mass and the plain old red blood cell count (RBC) that you get in a CBC do not differentiate between benign mature red cells and the malignant mature red cells you see in polycythemia vera. So patients with any kind of polycythemia (whether it’s primary or secondary) will have an increased RBC mass/increased RBC.
Studying hematopathology can be a challenge. There are so many new words and concepts that it can seem overwhelming at times. (more…)
Hello to all pathology students everywhere – dental students, medical students, nursing and allied health students…and to anyone interested in pathology. My goal is to help you study pathology by providing useful tidbits of information, tips on how to remember things, and interesting asides. I hope you find this blog helpful!
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