When Barbara Baker noticed that Lord had developed a lump on his right cheek, she didn’t give it much thought. It was about the size of a cherry, and was not growing, bleeding, changing shape or color, or otherwise bothering the pig. It was only when Dr. Lawhorn, who was attending the potbellied pig symposium in Florida, visited her home and examined Lord’s lump that she became concerned. Dr. Lawhorn advised Barbara to have the lump removed and sent for pathologic examination. A few weeks later the surgery was performed. It was easy for the veterinary pathologist to identify the characteristic features of a mast cell tumor, but it was almost impossible for the pathologist, or anyone else for that matter, to offer an idea of what might happen now that the tumor was removed. We just don’t know enough about mast cell tumors in pigs to be able to predict their behavior.
When Barbara asked if I would be willing to write an article on mast cell tumors in pigs, I went to my files to see what I could find. There is precious little written about mast cell tumors in pigs, so at least I didn’t have to wade through a lot of material! In this article I will try to summarize what we do know about mast cell tumors in pigs and in other species.
First off, let me explain what a mast cell is. Mast cells are normal residents of the areas of the body that are exposed to what can be considered an “external” environment. This includes the skin, sinuses, the lining of the airways from the nose to the lungs, and the lining of the stomach and intestines. Mast cells are identified by their characteristic granules. The purpose of mast cells is to release the contents of their granules during infections. The granules of mast cells contain a variety of substances, many of which make blood vessels “leaky,” which helps other inflammatory cells to get to the site of an infection to try to clear it up. This normal role is often overlooked in discussions of mast cells, because mast cells are so often involved in allergic responses. Allergies can be considered a form of “healthy” inflammation gone awry. One of the substances that mast cells produce and release is histamine, which is the basis for the use of antihistamines in allergic conditions. Histamines cause vessels to be leaky, which leads to fluid accumulation and tissue swelling, and often cause an itching sensation in the area.
Tumors of mast cells, called either mast cell tumors or mastocytomas, are common in dogs, cats, and ferrets, and are much less common in horses, cattle, pigs and people. We know a lot about the behavior of mast cell tumors in dogs, cats, ferrets, and horses, but very little about their behavior in cattle and pigs. Such tumors are very uncommon in people, usually occurring in children, where they often regress on their own. In dogs, mast cell tumors are graded 1, 2 and 3, with grades 1 and 2 being relatively benign and generally cured by wide surgical excision, and grade 3 being malignant and likely to recur and/or spread. Mast cell tumors in cats are most often benign, although there is a less common malignant variant. Mast cell tumors in ferrets and horses are considered benign tumors. In cats, the most common mast cell neoplastic processes are skin tumors (that can be multiple), and an internal mastocytosis syndrome in which neoplastic mast cells infiltrate multiple internal organs. In the cat, these appear to be two distinct disorders.
Adding to the confusion is that there is a condition called mastocytosis, in which mast cells are increased throughout the body, creating havoc by producing their inflammation-promoting substances. In some cases the mast cells themselves are not thought to be neoplastic, but in others they are. I should define the term neoplastic here. Neo means new, and plastic means growth, so a neoplasm is a growth of new tissue. Neoplasia can be benign, meaning that the tumor does not invade or spread. Malignant tumors invade and/or spread through the body, causing what is often called cancer. The term cancer comes from the Latin word for crab, because the spread of cancer can resemble the spreading legs of a crab. And, to make matters worse, there is also a condition in which neoplastic mast cells circulate in the blood, known as mast cell leukemia.
The literature regarding mast cell disorders in pigs includes mast cell tumors, mastocytosis, and mast cell leukemia. Mast cell tumors of the skin or of internal organs are the most common mast cell problems in pigs, and have even been reported in young meat pigs examined at slaughterhouses. These tumors are not common in young pigs, though, with one study citing only 5 cases of mast cell tumors of the skin in 664 million pigs examined.
Barbara was able to find me pathology reports from three other potbellied pigs with mast cell tumors. Two were single tumors, similar to Lord’s, and another pig had multiple mast cell tumors in the skin. The ages recorded were around 7 years of age. The pig with multiple tumors had re-growth of three of the tumors following removal. So far, I have not seen any reports of internal mast cell tumors in potbellied pigs. But, given findings in other breeds of pigs, I suspect that this is a possibility. The behavior of mast cells tumors is often described as unpredictable, usually because we simply don’t know enough to be able to predict it. This is certainly the case with mast cell tumors in pigs. From what I can gather from the literature to date, mast cell tumors in pigs appear to be more similar to cats than to other species. That is, tumors that form in the skin may be multiple and can recur following incomplete excision, but they tend to stay in the skin. Tumors that form internally are not often associated with skin tumors. I hasten to add that this is still speculation, based on a very small number of reported cases of mast cell neoplasia in pigs. We still have a lot to learn about mast cell tumors in pet pigs.
So, what should you do if your pig develops a skin lump? My best advice is to have it examined by a veterinarian and removed as soon as possible. A mast cell tumor that is completely removed early on is far less likely to recur or to spread than is one that has been there for awhile. The veterinary surgeon will aim to remove the tumor as widely as possible, and removing a small tumor is much preferred to waiting for it to grow to a really worrisome size. Always insist on sending the sample for pathologic evaluation.
It is only by removing tumors and having them identified as mast cell tumors, and then following up on the pigs to see what happens, that we will be able to learn about the behavior of mast cell tumors in potbellied pigs. The efforts of people like Barbara Baker and of organizations like the Duchess Fund are to be lauded. Only by continuing to gather and examine data on disorders of potbellied pigs will we be able to learn more about these vexing tumors, as well as other problems that plague potbellied pigs.
Beth A. Valentine, DVM, PhD, is a board-certified veterinary pathologist on the faculty of the College of Veterinary Medicine at Oregon State University, Corvallis, OR.
Barbara Baker alipogundua kwamba Bwana alikuwa na maendeleo ya kamba juu ya shavu lake la kulia, yeye hakuwa na kutoa mawazo mengi. Ilikuwa na ukubwa wa cherry, na haikuwa ikikua, ikitoka damu, ikibadilisha umbo au rangi, au kwa njia nyingine kusumbua nguruwe. Ni wakati tu Daktari Lawhorn, ambaye alikuwa akihudhuria mkutano wa nguruwe wenye tumbo la mviringo huko Florida, alipomtembelea nyumbani na kuchunguza kifundo cha Bwana kwamba akawa na wasiwasi. Dakt. Lawhorn alimshauri Barbara aondole kibofu hicho na kukipeleka kwa daktari wa magonjwa. Majuma machache baadaye upasuaji ulifanywa. Ilikuwa rahisi kwa mtaalamu wa magonjwa ya wanyama kutambua sifa za uvimbe wa seli za mast, lakini ilikuwa karibu haiwezekani kwa mtaalamu wa magonjwa, au mtu mwingine yeyote kwa jambo hilo, kutoa wazo la kile kinachoweza kutokea sasa kwamba uvimbe huo umeondolewa. Hatujui vya kutosha kuhusu uvimbe wa chembe za mast katika nguruwe ili kuweza kutabiri tabia yao. Barbara aliponiuliza kama ningependa kuandika makala kuhusu uvimbe wa chembe za mast katika nguruwe, nilienda kwenye faili zangu kuona kile ningeweza kupata. Kuna machache ya thamani iliyoandikwa kuhusu uvimbe wa seli ya mast katika nguruwe, hivyo angalau sikuhitaji kupitia nyenzo nyingi! Katika makala hii, tutajaribu kuelezea kwa ufupi kile tunachojua kuhusu uvimbe wa seli za mast katika nguruwe na katika spishi nyingine. Kwanza, hebu nieleze ni nini chembe ya mast. Chembe za mast ni wakazi wa kawaida wa maeneo ya mwili ambayo yanafunuliwa kwa kile kinachoweza kuchukuliwa kuwa mazingira ya "nje". Hii inatia ndani ngozi, sinusi, utando wa njia za kupumua kutoka pua hadi mapafu, na utando wa tumbo na matumbo. Chembe za mast zinatambuliwa kwa chembe zao za kipekee. Kusudi la chembe za mast ni kutolewa kwa yaliyomo katika chembe zao wakati wa maambukizo. Granules ya seli ya mast ina aina mbalimbali ya vitu, wengi ambao kufanya mishipa ya damu "leaky", ambayo husaidia seli nyingine uchochezi kupata tovuti ya maambukizi kujaribu kuondoa. Kazi hii ya kawaida mara nyingi hupuuzwa katika majadiliano ya chembe za mast, kwa sababu chembe za mast mara nyingi huhusika katika majibu ya mzio. Madhara ya mzio yaweza kuonwa kuwa aina ya uvimbe "wa afya" ulioenda vibaya. Miongoni mwa vitu ambavyo chembe za mast hutengeneza na kutolewa ni histamine, ambayo ni msingi wa matumizi ya antihistamines katika hali ya mzio. Histamini husababisha mishipa ya damu kuvuja, na kusababisha mkusanyiko wa maji na uvimbe wa tishu, na mara nyingi husababisha hisia ya kukwaruza katika eneo hilo. Tumors ya mastocytes, au mastocytomas, ni ya kawaida katika mbwa, paka, na ferrets, na ni chini ya kawaida katika farasi, ng'ombe, nguruwe na watu. Tumesoma sana kuhusu tabia ya mastocytes katika mbwa, paka, farasi, na farasi, lakini kidogo sana kuhusu tabia yao katika ng'ombe na nguruwe. Uvimbe kama huo ni wa kawaida sana kwa watu, kwa kawaida hutokea kwa watoto, ambapo mara nyingi hufifia wenyewe. Katika mbwa, uvimbe wa seli ya mast ni daraja la 1, 2 na 3, na daraja la 1 na 2 ni benign na kwa ujumla huponywa kwa upasuaji wa upasuaji, na daraja la 3 ni mbaya na uwezekano wa kurudi na kuenea. Uvimbe wa chembe za mast katika paka mara nyingi ni mzuri, ingawa kuna tofauti mbaya isiyo ya kawaida. Uvimbe wa chembe za mast katika punda-milia na farasi huonwa kuwa chembe za kawaida. Katika paka, mchakato wa kawaida wa neoplastic ya seli ya mast ni uvimbe wa ngozi (ambayo inaweza kuwa nyingi), na ugonjwa wa mastocytosis ya ndani ambayo seli za mast ya neoplastic huingia katika viungo vingi vya ndani. Katika paka, hizi huonekana kuwa magonjwa mawili tofauti. Kwa kuongezea, kuna hali inayoitwa mastocytosis, ambayo huongeza idadi ya chembe za mast katika mwili wote, na kusababisha uharibifu kwa kutokeza vitu vinavyochochea uvimbe. Katika visa fulani chembe za mast zenyewe hazifikiriwa kuwa neoplastic, lakini katika nyingine ni hivyo. Ninapaswa kufafanua neno neoplastic hapa. Neo inamaanisha mpya, na plastiki inamaanisha ukuaji, kwa hivyo neoplasm ni ukuaji wa tishu mpya. Neoplasia yaweza kuwa ya aina nzuri, ikimaanisha kwamba uvimbe hauvami au kuenea. Uvimbe mbaya huingia na kuenea katika mwili, na kusababisha kile kinachoitwa kansa. "Jina ""Kansa"" linatokana na neno la Kilatini ""crab"" ambalo linamaanisha ""kamba,"" kwa sababu ugonjwa wa kansa unafanana na miguu ya kamba." Na, ili kufanya mambo yawe mabaya zaidi, kuna pia hali ambayo chembe za mast za neoplastic huzunguka katika damu, inayojulikana kama leukemia ya chembe za mast. Maandishi kuhusu magonjwa ya chembe za mast katika nguruwe ni pamoja na uvimbe wa chembe za mast, mastocytosis, na leukemia ya chembe za mast. Matatizo ya seli za mast ya ngozi au ya viungo vya ndani ni matatizo ya kawaida ya seli za mast katika nguruwe, na hata yameripotiwa katika nguruwe wachanga wa nyama waliochunguzwa katika mashamba ya nyama. Ugonjwa huu ni wa kawaida kwa nguruwe wadogo, ingawa utafiti mmoja ulitaja kesi tano tu za uvimbe wa seli za mast kwenye ngozi katika nguruwe milioni 664 zilizochunguzwa. Barbara aliweza kunipatia ripoti za magonjwa kutoka kwa nguruwe wengine watatu wenye tumors za seli za mast. Mbili zilikuwa uvimbe mmoja, sawa na ule wa Bwana, na nguruwe mwingine alikuwa na uvimbe mwingi wa chembe za mast katika ngozi. Umri wa waliotajwa ulikuwa karibu miaka saba. Nguruwe mwenye uvimbe mwingi alikuwa na ukuaji wa tatu wa uvimbe baada ya kuondolewa. Hadi sasa, sijaona ripoti yoyote ya uvimbe wa ndani wa chembe za mast katika nguruwe wenye tumbo la chini. Lakini, kwa kuzingatia matokeo katika jamii nyingine za nguruwe, ninashuku kwamba hilo linawezekana. Tabia ya uvimbe wa seli za mast mara nyingi huelezwa kuwa haiwezi kutabiriwa, kwa kawaida kwa sababu hatujui vya kutosha kuweza kutabiri. Hii ni hakika kesi na mastoid seli tumors katika nguruwe. Kwa mujibu wa utafiti wa utafiti wa utafiti wa kisasa, tumors ya seli ya mast katika nguruwe inaonekana kuwa sawa na paka kuliko aina nyingine. Tumors zinazojitokeza kwenye ngozi zinaweza kuwa nyingi na zinaweza kurudi baada ya kuondolewa, lakini huwa na mwelekeo wa kubaki kwenye ngozi. Mara nyingi uvimbe unaotokezwa ndani ya mwili hauhusiani na uvimbe wa ngozi. "Ninaongeza kuwa hii bado ni uvumi, kulingana na idadi ndogo sana ya kesi zilizoripotiwa za ""mast cell neoplasia"" katika nguruwe." Bado tuna mengi ya kujifunza kuhusu uvimbe wa chembe za mast katika nguruwe wa kufugwa. Kwa hiyo, unapaswa kufanya nini ikiwa nguruwe wako atapata uvimbe wa ngozi? Ushauri wangu bora ni kuupima na daktari wa mifugo na kuondoa haraka iwezekanavyo. Ugonjwa wa seli ya mast ambao umeondolewa kabisa mapema ni uwezekano mdogo wa kurudi au kuenea kuliko ule ambao umekuwapo kwa muda. Mpasuaji wa wanyama atajaribu kuondoa uvimbe kwa kiasi kikubwa iwezekanavyo, na kuondoa uvimbe mdogo ni bora kuliko kungojea ukuaji wake uwe mkubwa sana. Sikuzote sikiliza juu ya kutuma sampuli kwa ajili ya tathmini ya pathological. "Ni kwa kuondoa tumors na kuwa na wao kutambuliwa kama ""mast cell tumors"" na kisha kufuatilia juu ya nguruwe kuona nini kinatokea, kwamba tutaweza kujifunza kuhusu tabia ya ""mast cell tumors"" katika nguruwe potbellied." Jitihada za watu kama Barbara Baker na mashirika kama Duchess Fund zinastahili kusifiwa. Ni kwa kuendelea kukusanya na kuchunguza data juu ya magonjwa ya nguruwe wa tumbo la chini tu tutaweza kujifunza zaidi juu ya uvimbe huu wa kusumbua, pamoja na matatizo mengine ambayo yanawatesa nguruwe wa tumbo la chini. Beth Valentine, MD, PhD, ni mtaalamu wa patholojia ya mifugo katika Chuo cha Tiba ya Wanyama katika Chuo Kikuu cha Jimbo la Oregon, Corvallis, OR.