Cytologic and Histologic Features of Malignant Tumors

00:01 We can use both histologic features and cytologic features, to say whether something is malignant or not.

00:10 So, the difference between cytology and histology.

00:13 Cytology are single cell smears, that we get from sputums or from scraping say, the cervix, or by just rubbing a tumor on a glass slide, we can get and look at individual single cells, that's cytology.

00:28 On the other hand, if we carve something out, take a section of that, put it in a paraffin block and take slides, that's histology.

00:35 So, we can use both of those features, to decide whether something is malignant or not.

00:41 So, what I'm showing you here, are the cytologic features of an abnormal cell and in the first panel that you're seeing, we're seeing normal bronchial epithelium, that were derived from a bronchoscopy and then an aspirate and these came out.

00:57 The nuclei are basaloid, they're oriented towards the base of the cells, these are top () cells and on the surface, they have cilia.

01:04 So, it's a well differentiated cell, with a normally organized nucleus near the base.

01:10 And the size of the nuclei are pretty much comparable, between each individual cell and the nature of the chromatin structure is, characteristic for this cell type.

01:20 There is some ongoing translation, so, there is some, heterochromatin, there's kind of ill-defined nucleoli, but overall, this is well differentiated and well behaved, normal bronchial epithelium.

01:38 In comparison, here is a cytology smear, from a patient who has, non-small cell lung carcinoma.

01:45 These cells that you're seeing now, were derived from the same ones, that you see above, but they don't look anything like that.

01:53 First of all, there's no orientation in terms of what's up and what's down, we don't have the same cytoplasmic orientation of nuclei near the base.

02:04 We have cells that are very large and not only that, but heterogeneous, they have very, very prominent nucleoli, that are being indicated here.

02:14 They have irregularly clump chromatin.

02:16 There's a lot of variation from cell to cell.

02:19 There's also a markedly increased nuclear to cytoplasmic ratio.

02:23 So above, you can see that, the nucleus comprises, maybe, a third to a half of the cell volume.

02:30 On the bottom, although it's hard to see the cytoplasm, the nucleus is filling up perhaps 80 to 90% of that cell volume.

02:39 So, this is how we as pathologists, make the distinction between benign and malignant.

02:46 So, just in words, but we just talked about on the left-hand side.

02:50 In tumors, the cytologic features that we're looking for is an increased nuclear size.

02:56 This reflects aneuploidy, so increased numbers of chromosomes, abnormal chromosomes, etc., with an increased DNA content, so,the nuclear size is much bigger.

03:06 There's loss of the specialized cytoplasm for specific functions.

03:09 So, our normal bronchial epithelium, top left panel, it's got cilia, because that's what normal epithelial cells in the lung airways have.

03:18 The bottom ones, that cilia, is no longer being expressed, it doesn't care that it would normally have that differentiation pathway, it just now wants to grow.

03:29 There will also be, as I've already remarked, a high nuclear cytoplasmic ratio, called the N:C ratio in the cells.

03:36 They are mostly nuclei, with a little bit of cytoplasm, just enough to keep them alive.

03:42 There's an irregular nuclear membrane and clumped chromatin.

03:45 So, the chromatin is very heterogeneous, and this reflects abnormal organization of the DNA and frequently, we have enlarged nucleoli and that means that we're making more RNA, and ribosomes in particular, so they enlarge nucleolus.

04:05 So, those are the cytologic features, comparing normal vs. abnormal or normal vs. malignant.

04:14 There are also histologic features.

04:16 So, things that we can see on histology.

04:19 So, pleomorphism is one that we use all the time.

04:22 In most tissues.

04:23 Again, there are exceptions, but in most tissues, the cells are uniform, in terms of their cell size, nuclear size and their shape.

04:36 But when it becomes quite variable, in terms of nuclear size and shape or cell size and shape, we call that pleomorphic.

04:43 Tumors, again, just on, like we said on cytology, on histology typically have a high nuclear cytoplasmic ratio.

04:53 The nuclei tend to be hyperchromatic with increased nuclear staining, so, there's more haematoxylin, because there's greater DNA content.

05:02 There is a loss of polarity for epithelial structures.

05:05 So, instead of knowing what's up and what's down, these tumor cells are just growing and they lose that orientation.

05:16 There's loss of identifiable differentiation.

05:18 Again, tumor cells don't care that their original cell was intended to make keratin or to make smooth muscle or to make whatever.

05:29 It's now just interested in growing.

05:31 So, a lot of the usual function of that cell has been lost.

05:38 There are many mitotic figures in histology, and abnormal mitosis, including those with the Mercedes-Benz sign.

05:46 They tend to have invasive and infiltrative growth pattern, which, we can see very easily or pretty easily on histology and then metastatic disease.