Types of Neoplasms, and Making a Diagnosis

by Richard Mitchell, MD, PhD

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    00:01 So, types of neoplasms.

    00:02 And it runs the gamut from at the top benign, to at the very bottom, metastatic.

    00:08 So, you can have pre-malignant low-grade dysplasia.

    00:11 You can have in situ malignant dysplasia, high-grade dysplasia, which is basically, in situ carcinoma.

    00:18 You can have invasive malignant tumors and you can have metastatic tumors.

    00:25 Importantly, most benign tumors and we've talked about this previously, but most benign tumors, say like a lipoma or a leiomyoma, do not become malignant.

    00:36 It's usually a separate cell, that starts going through a clonal expansion, acquires additional mutations.

    00:44 Most of the time if you have a mole, a benign nevus on your skin, it's not going to turn into a malignant melanoma.

    00:51 All right, so the vast majority of benign tumors never go bad.

    00:56 So, how do I establish a diagnosis? What are the things that I need to do? On the right-hand side is just a well to moderately differentiated adenocarcinoma, with a substantial number of inflammatory cells.

    01:10 The adenocarcinoma are those glandular-like elements, around that mucinous core chun and I know, I can say that, this is in the lung, pretty with great assurance, because there's also anthracotic pigment, the black pigment down on the lower right-hand side.

    01:26 There is some desmoplastic response and there are signs of tumor cell focal necrosis, say at the very bottom.

    01:34 When I get a specimen, in any surgical specimen I first need to determine, that I have an adequate amount of material to do what I need to do.

    01:44 Now, this is a fairly big chunk, that came out of a partial pneumonectomy, but sometimes I get little tiny cores, basically, fine needles, that pull out maybe 50 cells, I may not have adequate tissue to render an appropriate diagnosis.

    02:02 I definitely as a pathologist, read the clinical history, I cannot make a diagnosis in the absence of that.

    02:10 It's important for me to know the gender, the age, the site where things are being sampled etc.

    02:17 Also, any past medical history, past exposures, because all of those can potentially influence, what I'm seeing down the microscope.

    02:25 And sometimes, if I know through the clinical history, the patient has had lots of radiation.

    02:30 Some very funny-looking cells, that I see under the microscope, actually, just be a typical fibroblast and not tumor.

    02:38 Whereas, if this same patient who has not been radiated and I have some very funny-looking cells, maybe even with a few other features, I could say well maybe that's a fibrosarcoma.

    02:50 So, clinical history, is actually very important part of the pathologic diagnosis.

    02:55 I have to do a macroscopic exam, I have to look at the entire piece of whatever I have and determine margins and determine location and determine size, etc., etc.

    03:08 So, a macroscopic exam is part of my diagnosis, clearly the microscopic exam is a very important part, there are many things I can see down a microscope, that are not apparent at any other level.

    03:19 I will need to run in many cases ancillary tests, I'll do immunohistochemistry, I might do electron microscopy, I will do molecular diagnostics, I might do cytogenetics.

    03:28 So, there are other things that will help me, establish the very best diagnosis, for my surgical or oncology colleagues.

    03:36 And then I have to put the whole story together.

    03:39 So, everything that you see above there, all those six boxes, I need to put together into a coherent diagnosis and be able to convey that, as well as my interpretation of everything, to the oncologist or the surgeon.

    03:54 So, what kind of tricks can I do as a pathologist? There are a whole bunch of ancillary technologies, that we can apply, to tissue.

    04:03 So, first of all, we can do the traditional staining, this the top panel is showing an H&E a hematoxylin and eosin staining of an adenocarcinoma, that's what the pointer, the arrow is pointing to, is a little cluster of adenocarcinoma cells, they're actually signet ring cells, with mucin pushing the nucleus off to the side, surrounding it, is a whole collection of, lymphocytes.

    04:28 But when I look at this, I don't know whether that clearing, adjacent to the nucleus and the tumor cells is, mucin or is it glycogen, is it fat, that all makes a difference in terms of what kind of cell that might be.

    04:41 So, then I can do in the bottom panel a mucicarmine stain.

    04:45 A mucicarmine stain, is, the mucus, that kind of pink color, so, I'm able to identify just on a variety of special stains, what's going on.

    04:55 I can also do enzyme histochemistry.

    04:57 So, some cells have an intrinsic enzymatic activity and for example, in acute myelogenous leukaemia, which is being shown here, there is brown pigmentation in the cells, due to the activity of the myeloperoxidase present in the AML cells.

    05:16 So, if I add on a substrate for myeloperoxidase, I get this brown pigment and that's another way that I can determine, what I'm dealing with.

    05:24 In some cases, we go to electron microscopy, so, you're seeing an image of a transmission EM of a tumor cell, this happens to be a breast cancer cell, has a very prominent nucleolus, open chromatin, but sometimes on EM, there will be features that will allow us to say, “Oh, this differentiation pattern is more like say skeletal muscle and features that we might not ever see, on the regular routine histochemistry.” We can do a variety of immunohistochemical stains.

    05:55 This is where I'm taking an antibody against a specific entity.

    05:59 That antibody is coupled to an enzyme that I can then measure, by adding on appropriate substrate.

    06:04 So, everything that's brown that you're seeing here, is because an antibody bound to a particular antigen.

    06:10 In the top panel, is a cytoplasmic antigen, so, this could be a cytokeratin or this could be some other component that is unique and intrinsic to a particular cell.

    06:21 So, for example, cytokeratin 7, is a cytokeratin, that's normally found in tumors that originate above the diaphragm.

    06:30 CK20, is a cytokeratin that's found in malignancies that occur, below the diaphragm.

    06:37 So, if I'm not sure where this came from, I can do a CK7 and a CK20 stain and be able to determine between the two.

    06:46 The bottom panel is showing an antibody directed against the transcription factor and often, there may be an upregulation of a transcription factor associated with certain tumors.

    06:56 In this particular case, I believe, that this is, a TTF-1.

    07:00 So, it's a thyroid transcription factor 1, that is associated with thyroid and lung cancers and there's a very market upregulation in that tumor and I see it within the nucleus, because that's where all good transcription factors should go.

    07:15 So, using these immunohistochemical tricks, I can very nicely ascertain cell of origin and be able to point clinicians in various directions.

    07:26 We can also do in situ hybridization.

    07:28 This is where we take, nucleotide probes that look for specific portions of the DNA.

    07:36 What's shown up above is an oncogene over expression, where there is too much of the red signal, indicating for example that this could be a MYC over amplification, (MYC) MYC over amplification, so that's just an example.

    07:53 But we can also use it to see whether there is a translocation, so, normally, say there's one gene over here, on one chromosome and another gene over here on another chromosome and I can put in a probe that stains green for that one and red for that one, normally in every cell, I'd see a separate green dot and a separate red dot.

    08:14 If, however I see the red and green dots together, I know that I've had genetic translocation and now fusion of those two chromosomes bringing the two signals together and that frequently happens in a number of tumors, for example, the BCR/ABL translocation that occurs, in chronic myelogenous leukaemia.

    08:34 We can do a cytogenetic analysis.

    08:37 These are very, very cool.

    08:38 You basically can paint each chromosome with its own unique color and that's what you're seeing on the left-hand side, is that we're seeing all those various chromosomes, that are painted.

    08:49 What shouldn't happen, unless there are translocations, is that, you shouldn't have two colors on one chromosome and several of the chromosomes in there have, multiple colors on one bar.

    09:00 That means that there have been numbers of translocations and knowing what color, goes with which chromosome, I can say exactly what translocations have occurred.

    09:10 I can also do this just on a metaphase smear and that's what on the lower right.

    09:15 Is just a metaphase smear of chromosomes and we can with various banding staining patterns, be able to identify, what translocations have occurred.

    09:25 We can also do flow cytometry, which is, basically, taking antibodies, coating single cells, running them past a laser scanner that says, that cell is positive for that particular marker or negative for that particular marker, we do that all the time for leukaemia’s and lymphomas, to determine clonality.

    09:45 And then finally, in the 21st century, we are doing a lot of molecular diagnostics, we're doing DNA sequencing, deep DNA or RNA sequencing, to get signatures of mutations, to identify over-amplifications or loss of heterozygosity.

    10:04 All of those things are going to be part of my toolkit, in making diagnoses.

    About the Lecture

    The lecture Types of Neoplasms, and Making a Diagnosis by Richard Mitchell, MD, PhD is from the course Surgical Pathology of Tumors.

    Included Quiz Questions

    1. Benign tumors
    2. Invasive tumors
    3. High-grade tumors
    4. Tumors with highly anaplastic cells
    5. Tumors with high mitotic activity
    1. Clinical history, macroscopic and microscopic appearances, and ancillary tests
    2. Response to prior treatment
    3. Clinical history
    4. Macroscopic appearance
    5. Microscopic appearance
    1. An enzyme-linked antibody labels an antigen in or on the target cell.
    2. A covalent reaction occurs between the cells of the tissue and a brown pigment.
    3. Specific chromosomal changes occur, which helps to determine the cell origin.
    4. Oncogenes are revealed, which helps to identify the tumor.
    5. A routine histochemical reaction occurs using particular colored reactants.
    1. A laboratory method that is used to reveal the presence and distribution of specific nucleic acid sequences in the cells of the target tissue
    2. A laboratory method that is used to locate specific organelles in the cytoplasm
    3. A laboratory method that is used to detect specific protein antigens inside or outside the cells
    4. A laboratory method that is used to detect the presence of mucin inside the cell
    5. A laboratory method that is used to detect the presence of adipose tissue inside the cell
    1. To help detect chromosomal changes
    2. To help detect specific gene sequences
    3. To help detect specific protein antigens
    4. To determine whether a tumor is malignant
    5. To determine cell type

    Author of lecture Types of Neoplasms, and Making a Diagnosis

     Richard Mitchell, MD, PhD

    Richard Mitchell, MD, PhD

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