Introduction to Soft Tissue Pathology: Tumors in Lipid Tissue

by Carlo Raj, MD

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    00:02 Hello. Let’s take a look at soft tissue pathology.

    00:05 In soft tissue pathology, which technically comes under connective tissue diseases.

    00:11 What we will do is we’ll organize our thoughts so that you know that when a tumor arises from a particular part of a soft tissue that the nomenclature will tell you what kind of signs and symptoms you can expect in your patient. Let’s begin.

    00:25 Let’s say there’s a tumor arises in the connective tissue but it’s a fat, then the name will be lipo-, and of course if it would be a benign tumor, you’d call it lipoma whereas if it was liposarcoma, it would be obviously malignant.

    00:38 Fibroblasts then you’re thinking fibro-. If it’s from the muscle then you’d be using, if it’s benign, then you’re thinking leiomyo- whereas if its rhabdomyo- then you’re thinking skeletal muscle, and leiomyo- would be of smooth muscle type and the rhabdo- would be of the skeletal muscle origin.

    00:53 Nerves, obviously here you’d call it neuro-, and in the bones—the discussion that we’ve had in orthopedics, well then obviously you’re using the name osteo- for bone, chondro- for cartilage.

    01:06 There’s a table here to quickly demarcate the differences between benign and malignant.

    01:11 Histologically, in the description that you want to keep in mind as you describe the particular tumor that you’re looking for well if it’s benign then most likely small— now you know these are just general rules but doesn’t always have to be exactly like this.

    01:28 Malignant would be larger, in other words, highly proliferating, and the more malignant and more proliferative a malignant tumor then becomes, then you’re increased risk of course of then invasive.

    01:40 Benign tends to be superficial, malignant deep.

    01:43 Benign tends to be slow growing because of decreased mitotic rate.

    01:47 Malignant would be fast growing so obviously much more proliferative.

    01:50 If it’s benign, then you’re thinking about the cytoplasm being much more than the nucleus because the mitotic rate and the proliferation rate is much lower, whereas if it is malignant, then you can expect a lot of nucleic activity so therefore you can expect; therefore, to see quite a bit of well, nuclear activity, so therefore, “blue”—more nuclei.

    02:09 Your nuclear-cytoplasmic ratio will have increased when you’re describing tumors that are of malignant nature in general. Correct? A benign nuclei—well that would mean that the contours of the chromatin are smooth and inconspicuous nuclei whereas if its malignant, as you can expect, there’s increased proliferation and that increased nuclear activity which is quite prominent, is often times referred to as being “ugly.” If it’s benign, then the tumor tends to be well-circumscribed, or are exceptions of course.

    02:39 Malignant tends to be infiltrative—you’re worried about compromise of that membrane and invasion taking place.

    02:46 In malignancy, expect there to be increase, frequent mitoses.

    02:51 Metaphase is something that you’d be looking for in the nuclei and then necrosis is something that also takes place because of increased destruction of the cells.

    03:02 Our first soft tissue issue that we’ll take a look at that’s benign is called lipoma.

    03:08 Of course, lipoma referring to lipid, more common soft tissue tumor of adulthood.

    03:15 Well-circumscribed as you can expect because we know that it’s benign, most often subcutis of the proximal extremities or the trunk.

    03:25 If we take a look at the histologic picture to the right, you’ll notice these clear vacuoles that are appearing and these clear vacuoles represent the fact that they are filled with lipid, With well-circumscribed.

    03:39 . Soft, mobile and painless are descriptions that you’re looking for in terms of signs and symptoms from your patient or from you observing.

    03:52 If the lipoma is no longer benign, but with that said, I can’t say that the liposarcoma, which is the topic here, comes from lipoma. So be careful.

    04:05 So the most common sarcoma of adults arguably is liposarcoma.

    04:11 Almost never seen in children. Age is middle age and above.

    04:15 Arise in the deep tissue whereas lipoma was superficial with subcutis of the proximal extremity.

    04:22 Liposarcoma will be deep, in other words, there’s possibility of increased infiltration and worry about invasion, and if there’s invasion, sarcomas of course tend to then spread via ________ route.

    04:33 They do have the characteristic lipoblasts, which I’ll show you in a second, and so therefore, what I mean by this is the well-circumscribed type histologic picture that I showed you earlier for lipoma, in which yes, you find your vacuoles that are clear, but you’ll compare that to what I’m going to show you next, which is lipid vacuoles indented with the central nucleus because of these cells that are filled with lipid.

    04:58 Liposarcoma. As I said, be careful.

    05:01 Lipoma will be the benign, liposarcoma would be the malignant.

    05:05 It doesn’t mean that the liposarcoma arose from the lipoma. Be careful. Most of the time they do not.

    05:10 There is 1 major exception I’ll tell you now, and that’s your chondrosarcoma.

    05:16 The chondrosarcoma may arise from enchondroma that would be 1 big exception in which, at times, you have a malignant tumor there—a bone tumor, a cartilage bone tumor that is arising from your benign cartilage tumor.

    05:32 Here are the lipoblasts that I promised that I would show you.

    05:36 If you take a look in the middle here, we have these big, plump, fat cells and then in the periphery are the nuclei.

    05:43 Rather characteristic of liposarcoma whereas earlier when I showed you a picture of lipoma, it definitely did not look as dangerous, as congested as which.

    05:54 On the same token, I want you to keep in mind a differential of liposarcoma known as nodular fasciitis.

    06:03 So nodular fasciitis is a reactive pseudosarcoma.

    06:08 It has nothing to do with malignancy.

    06:10 Now you would have these plump fibroblasts kind of like the picture that I showed you earlier, but that would basically be the only, only similarity.

    06:18 The history would be completely different from that of liposarcoma.

    06:22 A nodular fasciitis patient often times give you a history of trauma, and wherever that trauma might have taken place, you have rapid growing a mass on the forearm, for example well, like a sarcoma, you would expect there to be increase in proliferation, you would see increased mitoses, and you’d find a myxoid background.

    06:44 Here’s a picture of nodular fasciitis fasciitis in which these may then appear as being lipoblasts, but they’re not.

    06:52 And what you’re focusing upon are these green arrows, and those green arrows are then pointing to the areas of mitoses that are increased, and specifically metaphase, in which the chromosomes are lined up right smack dab in the middle about to divide.

    07:07 History of trauma is what you’re looking for most likely in nodular fasciitis.

    About the Lecture

    The lecture Introduction to Soft Tissue Pathology: Tumors in Lipid Tissue by Carlo Raj, MD is from the course Muscle and Soft Tissue: Pathology. It contains the following chapters:

    • Introduction to Soft Tissue Pathology
    • Tumors in Lipid Tissue

    Included Quiz Questions

    1. Rhabdomyosarcoma
    2. Rhabdomyoma
    3. Leiomyoma
    4. Leiomyosarcoma
    5. Liposarcoma
    1. Well-circumscribed
    2. Fast-growing
    3. Frequent mitoses
    4. Infiltrative
    5. Containing large cells with irregular nuclei
    1. Lipoma
    2. Liposarcoma
    3. Rhabdomyosarcoma
    4. Leiomyoma
    5. Leiomyosarcoma
    1. Nodular fasciitis
    2. Lipoma
    3. Liposarcoma
    4. Rhabdomyoma
    5. Rhabdomyosarcoma

    Author of lecture Introduction to Soft Tissue Pathology: Tumors in Lipid Tissue

     Carlo Raj, MD

    Carlo Raj, MD

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