Characterization of a Malignancy by Histotype, Cytogenetics, and Molecular Features

00:00 So, it's important that we in many cases be able to identify a “Histotype.” What was the cell of origin of this tumor, because the treatment options will vary depending on where it came from.

00:16 So, we may want to identify the lineage and the differentiation or histologic pattern of that lineage.

00:24 Here's an example.

00:25 So on H&E, this looked like a spindle cell tumor, with a lot of other mononuclear cells in it.

00:33 I stained it up with desmin, so that's the brown stain, this is an immunohistochemical stain.

00:39 And that spindle cell neoplasm, we would otherwise call a malignant fibrous histiocytoma, I can actually now say, it's much more likely to be a rhabdomyosarcoma or have sarcomas differentiation and that will actually have important prognostic information attached to it.

01:00 So, if we look at all malignant fibrous histiocytomas, which tend to do not well overall, we can also, distinguish who's going to do worse out of that category, so, if it's a non-myogenic tumor, the half-life that where 50% of the patients will have died, is out at six years, if it's a myogenic tumor, that half-life is more like two years.

01:29 So, it's important to be able to distinguish, where did the tumor come from, what is the original mother cell? I'm also in the same way going to be able to say, which ones are going to do better or worse, based on for example in this case cytogenetics.

01:46 So, this is an acute myelogenous leukemia, all the white cells that are on this peripheral smear, represent AML leukemic cells, they have a very coarsely clumped chromatin, they've got irregular nuclear contours, they have increased nuclear cytoplasmic ratio, they have all the features that we'd like to see for AML and we could also mark them with various flow cytometry markers.

02:12 But then, if I do the cytogenetics I can also cubby-hole them, into favorable or adverse prognostic outcomes.

02:21 If there's a translocation of chromosomes 15 or 17 or 8 and 21 or an inversion, those all tend to do better, than AML’s that have a very complex cytogenetic profile, with many, many translocations.

02:41 So, I just have those single translocations, then they do better than if they have complex translocations.