---start path.lec.04.28.97---- dr weber neoplasia he knows we're unhappy that this is the last segment of the course, but in about three weeks from the end of finals we'll find that life is not as much fun...we'll really miss room 13, dr spear, dr bovee, etc etc. really. no kidding. you'll see. oh, ok, it's a total lie. NEOPLASIA: we have to define some things first. basic and practical material will be mixed together. NEOPLASM: any new and abnormal tissue growth. the term CANCER is usually reserved for a MALIGNANT neoplasm MALIGNANCY means the new and abnormal tissue growth can invade tissue, locally cause destruction, and metastasize. when you talk about a TUMOR, 20-30 yrs ago, tumor meant anything presenting as a swelling, but now, tumor usually refers to any NEOPLASM. not everything presenting as a swelling is automatically a neoplasm. Could be a cyst, a hematoma, etc. granulomatous inflammatory response can also present as a swelling, but are not neoplastic. BENIGN TUMOR is a tumor that tends to be localized in the tissue, does not locally invade surrounding tissue, and cannot metastasize. there are other histological criteria as well, but LOCALIZED, NONINVASIVE, NON-METASTATIC are major criteria. learn the names of tumors, both benign and malignant. not very hard. TISSUE BENIGN MALIGNANT surface epithelium papilloma carcinoma glandular epithelium adenoma adenocarcinoma [IF surface epithelial tumor starts to grow with some kind of glandular pattern, could be called an adenoma. some surface epi can grow in this pattern. but most of the time, surface epithelial tumors project from the surface as a papilloma.] CT/mesenchymal something-oma something-sarcoma eg fibroma fibrosarcoma chondroma chondrosarcoma lipoma liposarcoma there is a list of more common tumors in the handout. go over them and make sure you know what they are called (this is on old exams...) THIS WILL BE ON THE FINAL EXAM! people make stuff up every year. try to know this, a few easy points... also, re LYMPHOID tissue....includes T cells, B cells, and histiocytes. most lymphoid tumors are actually B cell tumors unless originating in thymus. lymphoid tissue doesn't exist lymphoma, lymphosarcoma these are migratory cells, always metastatic. most common lymphoid tumors are B cell lymphoma/lymphosarcoma. but how does that differ from leukemia? LEUKEMIA is a tumor of BONE MARROW origin. can be of ANY bone marrow cells - granulocytic type, erythroblastic type, megakaryocytic type, or lymphocytic. usually one implies with a LEUKEMIA that it not only originates in BM, but eventually replaces all normal BM with these malignant leukemia cells, so animal gets very anemic. the potential problem comes in here - there are cases of lymphoma which present with a leukemic blood picture. a tumor could originate in LN, spleen, GI tract, but can present when you take a blood smear as a leukemia - there may be a high number of lymphoid type malignant cells circulating in the blood. so sometimes people say "leukemia" when they're really talking about a lymphoma. but unless the BM is involved and replaced, it's not really a leukemia, it's a lymphoma with a leukemic blood profile. non-conventional definitions: lymphoma is really nonsense, b/c -oma means benign tumor, but everyone uses it to mean malignant. also, melanoma is used to refer to malignancy, eg MALIGNANT MELANOMA - really SHOULD be called melanocarcinoma, because it comes from epithelial type cells, but no one calls it that. ANAPLASIA- a lack of differentiation of the tissue you're observing as a neoplasm, so may be very hard to recognize the histological type involved. the more anaplastic the cells are, the more PLEOMORPHISM usually associated with the neoplasm. anaplastic cells are more like basal/stem type cells. PLEOMORPHISM - the individual cells take on a great variety of morphological characteristics. cells usually much larger than normal, nuclear:cytoplasmic ratio not the normal 1:4, but totally aberrant. when you have an anaplastic tumor with lots of pleomorphism, this ratio goes down...often more like 1:1. also very hyperchromatic - stains very dark, due to increased # of nuclei and increased amount of DNA. nuclear shape changes tremendously. may be very bizarre looking nuclei, with lots of mitotic figures. the more mitotic figures you see, the more likely it is to be a malignancy, although that's not always the case. very weird looking mitotic figures are also a part of pleomorphism. so differences in size/shape of cells and nuclei, prominent nucleoli, and hyperchromaticity are part of pleomorphism the more pleomorphic the cells are, the less likely they are to function normally. always when looking at tumor, think of what the source cell type might be....say it is a tumor of melanocytes. it should be making pigment, and look black. what tumors produce is good indication of origin of tumor. the more of the product they make, the more differentiated they are, more likely to be benign. if more anaplastic, less differentiated, less likely to make product. any questions? now we're going to go into ONCOGENES argh argh argh argh argh. we found out a number of tumors were produced by viruses, at about the turn of the century. thought we could make a vaccine. worked with viruses in birds and mice. some viruses would induce tumors very quickly - eg w/in a few weeks. they called these "rapidly transforming oncogenic viruses" - then, people looked at DNA of the viruses and found a particular sequence that was responsible for inducing the neoplasm. they called these fragments of viral DNA "VIRAL ONCOGENES" and named them after the species in which they were discovered. V-SIS - simian sarcoma viral oncogene V-FES - feline sarcoma viral oncogene both of those are rapidly inducing tumor viruses. later, they were able to hybridize. found that in normal cells, there were sequences essentially very similar to these viral sequences. so for a long time, people didn't know what was going on. we called these "PROTO-ONCOGENES". somewhere in the evolution of these viruses, aeons ago, as the virus infected some organism which had these protooncogenes, the viruses picked up this part of normal host DNA. so now the virus has part of normal host DNA within it, due to this process of TRANSDUCTION. but there was a CHANGE IN FUNCTION AND CONFIGURATION of the normal host DNA during this process, and now when the virus infects cells, it brings into the host cell this oncogenic piece, which causes tumor in the host. VIRAL TRANSDUCTION - happened a long time ago, and now when virus infects host, it causes tumor because it is carrying this oncogene which was captured from host a long time ago. what are PROTO-ONCOGENES about in normal cells? they are involved in NORMAL CELL REGULATORY mechanisms. it's only called a proto-oncogene b/c it can be transformed into a CELLULAR ONCOGENE or c-onc. what are these "normal cell regulatory mechanisms" that proto-oncogenes are involved in? well...about 4 or 5 things. a normal proto-oncogene could code for GROWTH FACTORs, GROWTH FACTOR RECEPTORS (usually found in cell membrane), TRANSDUCERS that send message through cytoplasm via protein kinase C, phosphorylation, etc; could be NUCLEAR REGULATORY GENES (only occur in nucleus!) eg could make DNA BINDING PROTEINS; could work on mitochondria, eg could be MITOCHONDRIAL GENE which codes for a protein which works on inner leaflet of mitochondrial membrane, which has to do with apoptosis. examples: protooncogenes could code for the following: Growth factor- PDGF growth factor receptor: PDGF receptor transducer: G protein, RAS nuclear reg: Myc mitochondrial: bcl-2 - codes for protein that regulates apoptosis. so these proto-oncogenes are TOTALLY NORMAL but can become involved in neoplasia when slightly structurally altered by the virus or other means. CHEMICAL CARCINOGENS and RADIATION are the biggest factors which can change a proto-oncogene into a cellular oncogene (c-onc). this implies that the normal function of the proto-oncogene product is now exaggerated. since these products are involved in cell growth, we now call them c-oncs- nothing more than structurally altered p-onc which now overfunctions. often this involves a change in only one base, one AA - this can be enough to make this change. there is a way to recognize c-oncs...the main changes one can see in the genome is at the chromosome level...eg, reciprocal translocations, gene amplification (can actually be visualized...in many tumors can tell what sequence is involved) - both of those grossly can be seen. but most common change can't be seen grossly, can only be detected functionally - and that's ye olde point mutation as previously mentioned - eg, caused by chem carcinogen or radiation, which causes the functional problem. when we talk a bout induction of a neoplasm, realize it's not just one protooncogene becoming a c-onc....you need several sequential changes - it's a multi hit phenomenon. furthermore, we know that at same time, when going from normal cell to neoplastic cell, the cell starts to lose function of some suppressor genes. so you lose function of suppressor genes and you get change from p-onc to c-onc and TOGETHER you get change to neoplastic cell. one or the other alone doesn't usually induce neoplasia. it's pretty easy to go from p-onc to c-onc.... MOST tumors in man/animals are NOT CAUSED BY ONCOGENIC VIRUSES! most are caused by mutations from chem carcinogens or radiation or both, and we call those SPONTANEOUSLY OCCURING TUMORS. obviously they have a cause, the mutation, but cna't usually identify. but there are some known oncogenic viruses, divided into two groups: DNA and RNA viruses. RNA VIRUSES: slow acting viruses and rapidly acting viruses. most of the SLOW ACTING VIRUSES are leukemia viruses, tend to induce leukemia, but very slowly, eg in cats, FeLV - these do not carry a viral oncogene with them. the RAPIDLY ACTING VIRUSES eg rous sarcoma from avian system does carry within it a viral oncogene, so induces neoplasm right away DNA VIRUSES: HPV human papilloma virus. these viruses can induce tumors - usually warts. there are about 20 different papilloma viruses. EBV- epstein-barr - involved in mononucleosis and also also Burkett's lymphoma. HBV - hepatitis B - can transform liver cells - cause hepatocellular carcinoma or "hepatoma" which people use to mean liver malignancy for some reason. so, the viral oncogenes are really only contained in the RNA RAPIDLY TRANSFORMING VIRUSES. how does a DNA virus do it? it tends to insert into host genome some DNA that turns on the proto-oncogenes in the host in an exaggerated fashion. but the rapid RNA ones bring in an already changed p-onc, so can induce tumor right away. drawing picture on board of normal cell and the changes it goes through. first, you need some "irreversible genetic alteration" in the cell. this is the "cause" or the "initiating factor" and there are three recognized agents which do this: RADIATION, ONCOGENIC VIRUSES (rare) and CHEMICAL CARCINOGENS. after one of these occurs, you start to get initial transformation, "TRANSFORMATIONAL CELLS" - now these cells are able to grow continuously in culture, and when they are transplanted to a genetically identical individual they are able to grow as a neoplasm. just BEFORE this happens, there is a little "substage" in the transformation process called "immortalization" which means cell can continuously grow in culture but it canNOT grow into a tumor in a genetically identical individual. probably b/c the sequence of changes that is occuring hasn't fully occured. it's a step on the road toward neoplasm. maybe it's already had the p-onc become a c-onc,but hasn't yet lost suppresor gene activity, or something. common mistake: people think when a cell is transformed in vivo, that means that the cell will automatically start to divide. NOT TRUE. a transformed cell can sit in a stable tissue eg kidney or liver for a long time. what has to happen is SOMETHING must turn on division, and keep it going for several cell cycles until transformed state is fixed. so next step is INDUCTION OF MITOSIS which can be induced by nonspecific factors eg hormones that normally trigger it, or a nephrotoxin which kills some kidney cells so that others start to divide, so the transformed cell is among them, etc. in some tissues, this will occur as a matter of course eg in skin, resp tract, gi tract - there are always cells undergoing mitosis there, so it's likely that any transformed cell in those tissues will start dividing as a matter of course. then, you have a TUMOR CELL. this cell will start to divide, and will grow, and will still to some extent respond to normal cell regulatory controls. but then, as this tumor grows, an important step happens...as tumors grow, first of all, they are all MONOCLONAL IN ORIGIN - eg they all come from ONE transformed cell. but as they grow out, the clones of the original cell start to differ. they have different functional characteristics. all of a sudden, some of the daughters start failing to respond to normal signals, or making enzymes which invade local tissue, or whatever. you start having FUNCTIONALLY DIFFERENT CELL POPULATIONS which leads to the ability to INVADE and METASTASIZE. this FUNCTIONAL HETEROGENEITY is very important clinically. -----break---- many of the slides that are considered more critical are xeroxed on this handout. eg some flow charts, etc. schematic diagram of going from normal cell to malignant neoplasm. 1. mutations in genome of somatic cell - caused by inherited mutation, chemical, radiation, or virus. 2. activation of growth promoting oncogenes, alterations of genes regulating apoptosis, and inactivation of cancer suppressor genes all must occur 3. expression of altered gene products and loss of regulatory gene products 4. induction of mitosis 5. clonal expansion 6. additional mutations 7. functional heterogeneity 8. malignant neoplasm consider that occasionally a neoplasm develops that almost from its inception has characteristics of malignancy; others have a benign stage first. Normal cell diagram with asterisks marking oncogene activity. can see what p-oncs code for, etc.see handout. shows transducing signals going through kinase cascade w/phosphorylation, etc. EGF binds EGF receptor, which has tyrosine kinase on it - two oncogenes work at tyrosine kinase level. there are also oncogenes working directly on nucleus. most tumors in man and many animals have a change in Myc which works on nucleus. some transducing elements eg G proteins, or Raus sarcoma oncogene, through a sequence of events cause Ca++ release from ER, leading to phosphorylation of substrate, turns on cell. the NORMAL cell regulatory mechanisms are involved, but the function is changed - accentuation of growth processes, suppression of suppressor function. Rapidly transforming retroviruses: have this transduced protooncogene with them and carry it into cell. Raus sarcoma - invades cell, and protein coat comes off in endosome. RNA virus, so uses reverse transcriptase to make DNA copy of their own genomic RNA. that allows the copy of the RNA to masquerade as DNA, and to insert itself into the host genome. then the cell goes ahead and transcribes the genomic viral RNA and ALSO it transcribes mRNA for the virus, so it can make protein coats to assemble around the virus,a nd the virus buds off the cell surface to infect other cells. how do they induce neoplasia? well, you have the normal p-onc in host genome. these viruses historically picked up and changed the structure of the p-onc, so it carries it as a v-onc. when it infects the cell, the v-onc can transform the cell. the SLOW transforming viruses do not have this. how does this differ from slow acting virus? the slow acting virus doesn't have a v-onc. how does it turn cell on? well, normally, p-onc codes for say a GF or receptor or whatever. when virus comes in, it gets into nucleus - has reverse transcriptase, gets into host genome as above...but it can turn on the cell into neoplastic type, because viral genome is inserted NEAR the p-onc, and when it promotes its own transcription, it also changes the p-onc. this is called insertional mutagenesis. by inserting near the p-onc, and transcribing itself, it turns on the p-onc in exaggerated fashion, causing it to work weirdly, creating neoplasia. it doens't bring in a viral oncogene, it causes mutation in the p-onc. some tumors where you can actually see where a p-onc has been changed: p-onc turns into c-onc, associated with a virus although virus is not doing the actual transformation - in BURKETT'S LYMPHOMA, seen mostly in Africa, but also sometimes in western hemisphere. in almost all cases in africa, people who have the tumor have high Ab levels to Epstein-Barr virus (EBV). so somehow, those with Ab to EBV have high chance of getting this neoplasm. but there are additional environmental factors. in africa, we think possibly malaria or other infectious agents are a trigger. chronic infection eg by malaria or other organism causes lymphoid tissue to turn over rapidly, which would allow for transformation more quickly into neoplastic state. now, can't be just EBV causing it, b/c here sometimes we get Burkett's in people without EBV. so the change can sometimes be produced by things other than EBV eg radiation, chemical, other virus, etc. but in africa, this virus is strongly associated with this neoplasm. when you have Burkett's lymphoma, there is ALWAYS a reciprocal translocation occuring between chromosomes 8 and 14. the part where the myc oncogene is located gets moved from chromosome 8 to chrom 14. the part from chrom 14 goes over to chrom 8 so nothing is lost. but myc oncogene inserts right by Ig Heavy chain gene. this causes a problem....remember this is a B cell tumor. Ig heavy chain gene is almost always transcribing. now, we're inducing myc as well to transcribe. this results in neoplasm. this chromosomal translocation always occurs with Burketts lymphoma chronic myelogenous leukemia in man - "the philadelphia chromosome" - reciprocal translocation between chromosome 9 and 22...the abl oncogene from 9 moves over to 22, and somehow, by inserting, creates a "hybrid gene" at the "break point cluster region" - so it somehow involves other genes, causing a chronic myelogenous (granulocytic/eosinophilic) leukemia. all stem cells in BM have this translocation. final point on this is...GENE AMPLIFICATION can also cause neoplasia... N-myc which occurs in neuroblastoma, you can see one of two things....either you see that part of the chromosome near it becomes enlarged and stains weird due to duplication of genes, or you get duplicated fragments coming off, called "double minutes" (my-newts, he said), because cell is making extra copies of that gene, so now you get extra product because you have extra copies of the gene - either as the double minutes or as enlarged portion of chromosome. so RECIPROCAL TRANSLOCATION and GENE AMPLIFICATION can both be viewed, point mutation can't. PRACTICAL STUFF: looking at lesion, need to decide - is it a tumor? if so, benign or malignant? slide: lesion in inginal region of dog - about 1x1.5 cm. is mostly hairless, surface skin is eroded away - possibly growing so fast it is causing necrosis of overlying epi, or dog is licking it alot causing irritation and erosion of surface epi. very well defined...can palpate and clearly define borders of tumor, and that is characteristic of benign tumor. localized and well defined. also, history of slow development. also indicates benign growth. what kind of tumor is this? well, it is on the skin...surface epi, melanocytes, fibroblasts, endothelium, adnexal structures eg sweat/sebaceous glands, hair follicles, etc. histologically, we see some normal looking CT/collagen, and then closer to the surface we see very enlarged sebacous glands. they are well differentiated with normal looking basement membrane and normal looking gland cells. but they are BIG...there is NEW and ABNORMAL growth of this glandular tissue, so it is NEOPLASIA. but it is NOT ANAPLASTIC - it is well differentiated, is NOT PLEOMORPHIC - cells appear NORMAL IN SIZE AND SHAPE, with NORMAL nuclear:cytoplasmic ratio, no mitotic figures. very well defined, no infiltration into surrounding tissue. this is a SEBACEOUS ADENOMA!!!! :) slide: ventral surface of neck, between mandibles. well defined, dark, firm tissue mass, clearly defined borders. black/very dark mass. might be dark purple. partly hairless, no surface ulceration. about 3 cm diameter? what makes dark growth. melanocytes or blood. histologically, we see normal skin with normal adnexal structures, and then we see blood filled vascular spaces. many many little blood vessels lined by endothelium full of blood. there has been NEW and ABNORMAL growth of blood vessels. what made them grow? what's caused this? ENDOTHELIAL CELLS. but the endothelium is normal looking, well differentiated. so we call this a HEMANGIOMA - benign blood vessel tumor. normal looking blood vessels with normal CT in between. no visible pleomorphism or anaplasia slide: 6x8 cm mass in inguinal region w/multiple surface ulcerations and projecting smooth hairless tissue masses. lots of erythema over part of mass, probably from licking. poorly defined borders on palpation. histo: much more basophilic/cellular than other slide. there are some blood filled vascular spaces but they are irregular looking. we see pleomorphism and anaplasia. some nuclei are huge, some are small. there are prominent nucleoli, varying nuclear:cytoplasmic ratio but often 1:1 or less. also multiple mitotic figures. so much pleomorphism and anaplasia you can't tell what's going on. this is a HEMANGIOSARCOMA. note that the purple weird looking cells are ENDOTHELIAL CELLS and you can tell because in some places there are still blood filled vascular spaces. slide: looks like a big mac or something to me. part of a tail. there is a glistening, well defined, yellowish mass, very soft and greasy. 5x5 cm. minimal vascularity. histo: bunch of fat. call this a lipoma. benign overgrowth of fat cells. slide: ventral inguinal region of dog. GIANT mass covering whole area up to prepuce. firm, normal skin. histo: there are some fat cells. overall, lots of cells on slide. some pleomorphism, a few mitotic figures. in some areas, fat is accumulating. based on gross characteristics and this slide, on which we see some evidence of fat accumulation, we can call this liposarcoma. these cells are much less differentiated so there is considerable ANAPLASIA - only a few of them are normally accumulating fat. slide: saggital section of dog head with large bony mass on dorsal skull. this is a well defined mass within the bone. it's obviously new and abnormal and well differentiated and well defined. a benign tumor of osteocytes. an osteoma. histo: looks like nice, normal bone with marrow as well! some fibroblastic tissue. very clear border, no infiltration into the surrounding tissue. benign tissue often has capsule, but not ALL benign tumors have a capsule. mast cell tumors in dogs do NOT have capsules, so tthey often recur b/c you didn't get the whole thing. slide: malignant osteoblastic tumor. distal end of long bone in saggital section. there is very hemorrhagic, soft, bulging tissue mass which is infiltrating and has destroyed a lot of the cortex. obviously not normal. very hemorrhagic, so why is it osteoblastic? why not hemangiosarcoma? could it be hemangiosarcoma? Sure. it could be. need to look at histological section. histo: pleomorphic osteoblastic cells with prominent nucleoli, mitotic figures, etc. they are making osteoid so MUST be osteoblastic. but only SOME of them are doing it, so they are very anaplastic. so it must be an osteosarcoma. why is it so bloody grossly? b/c the bone marrow is very vascular, and there is a lot of tissue destruction, that's why. you have to check it out histologically to be sure what's going on. could also have been cartilage-based tumor (chondrosarcoma). ----end----