Tumor Nomenclature

by Richard Mitchell, MD, PhD

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    00:01 Okay. We're going to put on the hat of a pathologist now.

    00:05 We're going to try to distinguish between benign and malignant tumors.

    00:10 And it's not trivial, in fact that would be the job of pathologists, who have many, many years of training and so, the goal here is not to turn you into card-carrying pathologists, but rather to think about, the various aspects that make something benign, versus malignant.

    00:28 I’ll say right up front that, benign tumors might be a cause of death, so, for example a benign meningioma, in the brain that grows and grows and grows, could compromise normal vascular structures and you can die from that.

    00:43 On the other hand, there are many malignant tumors, even if you don't treat them or make them go away, will not kill you, so, many skin cancers, squamous cell carcinoma with the skin, basal cell carcinoma with the skin, are malignant tumors, they have molecular and genetic instability, but they typically will not kill you.

    01:04 So, the difference between benign and malignant, is not about whether it's fatal or not, important point.

    01:12 Okay, first of all though we have to talk about how we name these things.

    01:16 So, tumors contain proliferating neoplastic cells and supporting stroma, that's all part of what they are and then we want to name them, kind of based on whether we think they're benign or we think they're malignant and the features of each will become clear as we go further along.

    01:33 In general, for benign tumors, if we're going to name them, we will give them the cell of origin, so, if it comes from an adipocyte, it will be a “Lipo.” If it comes from a chondrocyte, making cartilage it's a “Chondro.” If it comes from a bone-forming cell, it's an “Osteo.” And we take those cells of origin and then add “O-M-A” at the end an “-oma” and that's our way of saying we have a benign lipoma or a lipoma, a benign tumor of the adipocytes or chondroma, a benign tumor of the chondrocytes, an osteoma, a benign tumor of osteocytes.

    02:16 You can also have benign skin tumors, a papilloma, so, that's generally our way of assigning benignancy, meaning that it's not going to be something that we have to worry too much about.

    02:28 However, like everything else in medicine, there are exceptions and an important set of exceptions are shown here.

    02:35 Melanoma, “Melan” means it comes from a melanocyte, and the “-oma” you would think, “Oh my God,” that's a benign tumor of melanocytes, no, it's a wildly malignant tumor. So, there are exceptions.

    02:47 Similarly, mesothelial-oma, mesotheli part, is from mesothelial cells and you'd say, “Oh my God,” that's a benign mesothelial cell tumor, well, no, it's a malignant tumor.

    02:59 So, the nomenclature that has been used and developed over the years and ever since pathology started doing things, isn't always completely uniform, and actually, everything I’m going to tell you in this particular talk, it's lies, it's all lies, because there are always exceptions.

    03:15 But if you can kind of remember the basic ground rules, you'll be right 99% 95% of the time, something like that.

    03:22 So again, another example of a violation of this kind of, cell of origin and -oma being benign, is a lymphoma.

    03:31 Lymphocytes forming a tumor, well it turns out lymphoma is malignant, so again, a bad name but we're stuck with it.

    03:39 Seminoma, is just another one.

    03:40 Seminomas are malignant tumors, of the of the seminiferous tubules and those are always malignant.

    03:47 Again, you would say, “Oh my God” it's semin-oma, it's benign, no, it's not, so, we just have to live with that.

    03:54 Okay, on the malignant side of the equation.

    03:58 For epithelial tumors that are malignant, we will call them, “Carcinomas” and you're saying, “Well, okay you're telling me lies again this ends with an -oma.” Yes, it does, but the “Carcin” on the front of that, indicates that it's cancer already, okay, and just because it ends in -oma doesn't mean it's benign, so, that carcinoma means it's an epithelial malignancy and then we will put things on the front of that.

    04:24 We will say, it's a squamous cell carcinoma, from squamous cell differentiation, or it's an adenocarcinoma, coming from glandular differentiation.

    04:35 The fact that we have “Carcinom” on the front of that, means that, it is malignant, even though it ends in -oma.

    04:43 So, go shoot me or shoot the pathologists that develop this.

    04:48 We will also identify, we may say that is it a pathocellular carcinoma, meaning it comes from liver cells or it is a hemangioendothelioma, which means it comes from endothelial cells.

    05:04 It's just the way you're going to have to learn to live with it.

    05:07 Then there are mesenchymal tumors, so these I mean again, I know that this means it's malignant, you now know because I'm telling you these are malignant.

    05:17 Mesenchymal tumors are called sarcomas, again, “It's oh my God it's ending with -oma, you told me that was benign.” Well okay, but it's the “Sarc” on the front of that, that makes it a malignant tumor.

    05:29 So, if you have a benign tumor of fat cells, that's a lipoma.

    05:36 If you have a malignant tumor of fat cells that's a liposarcoma, okay.

    05:42 If you have a benign tumor of chondrocytes, that's a chondroma.

    05:47 If you have a malignant tumor of chondrocytes, that's a chondrosarcoma and that's how we make that particular distinction.

    05:55 Other malignant names, that we have to deal with is lymphoma, we've already talked about that is a malignant tumor of lymphocytes and leukaemia’s means that it's a malignant tumor of circulating blood elements and although “Leuk,” is actually a root word meaning white blood cell, we will use that term leukaemia, when we talk about other blood-borne malignancies.

    06:22 And then melanocytes forming a melanoma, we've already talked about that as well.

    06:27 So, some of this makes some sense, some of this is, “Gosh you're telling me lies.” I think as you go along you will quickly be able to parse out, when we say something is benign, versus malignant and how we can distinguish that.

    06:44 And you'll quickly know that melanoma, mesothelioma, lymphoma, seminoma those are malignant.

    About the Lecture

    The lecture Tumor Nomenclature by Richard Mitchell, MD, PhD is from the course Surgical Pathology of Tumors.

    Included Quiz Questions

    1. Lipoma
    2. Melanoma
    3. Lymphoma
    4. Sarcoma
    5. Seminoma
    1. Adenocarcinoma
    2. Chondrosarcoma
    3. Lymphoma
    4. Leukemia
    5. Mesothelioma
    1. Neoplastic cells and supporting stroma
    2. Only neoplastic cells
    3. Only supporting stroma
    4. Nondividing cells and supporting stroma
    5. Highly differentiated cells

    Author of lecture Tumor Nomenclature

     Richard Mitchell, MD, PhD

    Richard Mitchell, MD, PhD

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