CASE REPORT

A Solitary Plasmacytoma in a Dog with Progression to aDisseminated Myeloma

S.J. LES-TER AND G.M. MESFIN*

SummarvSolitary plasmacytomas are rare

occurrences in dogs, consequentlytheir potential for malignancy is unde-termined. A solitary plasmacytomawas removed from the perianal regionof a dog. The dog was clinically nor-mal at that time, but was killed oneyear later as a result of hind limb stif-fness and uremia. At the postmortemexamination a disseminated myelomawas found, involving the vertebralcolumn, liver, spleen, bone marrowand visceral lymph nodes.

ResumeUn plasmocytome solitaire, chez unchien, qui evolua vers un myelomedissemine

Les plasmocytomes solitaires sedeveloppent rarement, chez le chien;on connait par consequent mal leurpotentiel de malignite. On enlevaun plasmocytome peri-anal, chez unchien que semblait cliniquement nor-mal, au moment de l'intervention. I1fallut cependant l'abattre, un an plustard, parce qu'il souffrait d'uremie etd'une raideur des membres pelviens.La necropsie revela la presence d'unmyelome dissemine qui affectait lacolonne vertebrale, le foie, la rate, lamoelle osseuse et les ganglions lym-phatiques visceraux.

IntroductionIn man, solitary accumulation of

plasma cells may occur as extramedul-lary expressions of multiple myelomasor as localized neoplasms distinct fromthe generalized disease. They mayremain quiescent or exhibit regional orgeneralized metastases but are usuallyconsidered potentially maligant (5).

The most common site is the upperrespiratory tract and oral cavity (4),but they are also found in the lowerintestinal tract, primarily the caecumand colon (6, 8).

There are few reports of solitaryplasmacytoma in the dog. A recentreport describes a solitary, apparently,benign plasmacytoma on the lip (2). Inthis report we describe a solitary plas-cacytoma which appeared one yearprior to development of a dissemi-nated myeloma. Electron miscros-copic examination was necessary todetermine the cell type of the originaltumor.

Clinical HistoryAn eight year old male Basenji dog,

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in apparent normal physical conditionwas presented for removal ofa mass (1x 2 cm) lateral to the anus. The subcu-taneous and moveable mass was surgi-cally removed and submitted to theWestern College of Veterinary Medi-cine (WCVM) for microscopic exami-nation. The dog made an uneventfulrecovery, but when examined one yearlater, posterior weakness, weight lossand polydipsia were found. An ankyl-osing spondylosis involving lumbarvertebrae 4 to 7 and a circumscribedlytic lesion on the spine of L4-werediscovered on radiographs. Elevatedblood urea nitrogen and serum creati-nine concentrations were also presentand the owners requested euthanasia.

PathologyOn microscopic examination, the

excised nodule contained colonicmucosa and adnexa diffusely infil-trated by discrete round cells (Figure1). These cells were densely packed insheets except at the periphery of thenodule where a ribbon arrangementwas apparent. Some reticular fibersseparated groups of cells. The cells hadround nuclei with peripheral nuclearclumping.The cellular morphology and loca-

FIGURE 1. Sections from the original subcutaneous mass from the eight year old male Basenji; arrowpoints to colonic epithelium. H & E. x150. Insert is an electron micrograph of individual cellsshowing cisternae of endoplasmic reticulum (arrow). x3600.

*Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7NOWO. Present address of Dr. Mesfin: Department of Pathology and Hygiene, School of Veterinary Medicine, University of Illinois, Urbana, Illinois61801.

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tion were consistent with a carcinoidtumor. Carcinoid tumors are com-posed of enterochromaffin cells whichshow argentaffinic or argyrophilicreactions (3). In this case, no argentaf-finic reaction was detected with Fon-tana silver stain. A mast cell tumor wasconsidered but metachromatic gra-nules were not detected with toludineblue. Plasma cells contain abundantrough endoplasmic reticulum whichstains red with methyl green-pyronin.This staining characteristic was notdetected in this case. Since the cellidentity was not established by specialstains, sections from the paraffinblocks were prepared for electronmicroscopy. Dilation of endoplasmicreticulum, peripheral nuclear chro-matin aggregates and intracytoplas-mic filaments were present (Figure 1).Based on these ultrastructural findingsthe tumor was identified as aplasmacytoma.Postmortem examination con-

firmed that the dog was in good physi-cal condition and without evidence ofthe previous tumor. The liver wasmarkedly enlarged with a diffuselymottled cut surface. The spleen andseveral lymph nodes were alsoenlarged. The bone marrow was firm,red and filled the medullary cavities ofall long bones. Thin white streaksextended through the cortex of bothkidneys. The distal lumbar segments

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FIGURE 2. Microscopic sections from eight yearold male Basenji showing invasion of hepaticportal areas and sinusoids hv numerous well

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of the vertebral column were fusedwith bone.On microscopic examination, mas-

sive plasma cell accumulations werefound in the portal areas of the liverwith extension into the lobules andsinusoids (Figure 2). The spleen, bonemarrow and lymph nodes had largenumbers of plasma cells showingbizarre nuclear shapes and sizes andoccasional binucleate forms (Figure3). Preparations from the fourth lum-bar spine also had plasma cell accumu-lations. Renal tubules and glomerulicontained an amorphous proteinace-ous material. The adjacent tubularepithelium was degenerate and therewas an increase in fibrous tissuethroughout the parenchyma. Congored stains of the amorphous materialdid not detect the presence of amyloid.The cells in the liver, spleen, lymphnodes and bone marrow were stainedby methyl green-pyronin.

DiscussionThe tumor was presented clinically

as a subcutaneous neoplasm. It wasnot possible to determine whether thiswas an extramedullary form ofdissem-inated myeloma or the primary tumor.The dog appeared healthy and tests fordetection of abnormal serum proteinsor Bence Jones proteins in the urinewere not performed. The dog alsoremained normal for almost a year~~~~~~~ :~~~~~4st . . *= j.,

FIGURE 3. Higher power view of splenic infil-trate in eight year old male Basenji. The cells arelarger and more bizarre than in the subcutane-ous mass (arrows point to binucleate cls H &

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after the initial diagnosis.Regardless of whether the solitary

tumor was primary or secondary it wasthe first clinical manifestation. It wasalso difficult to identify microscopi-cally since the cellular morphologywas unusual and the cells did not stainwith methyl green-pyronin. Electronmicrographs were necessary to iden-tify the cells as plasma cells. Theirultrastructure is similar to normalplasma cells (2, 8, 9). The nuclearchromatin is clumped around thenuclear membranes and the cells con-tain many parallel rows of endoplas-mic reticulum with dilatation of somecisternae. Intracytoplasmic filamentsare common and may representimmunoglobulin polymerization (10).Glycogen deposits have been noted inthe lip plasmocytoma from the dog (2).The disseminated tumor, with invol-vement of vertebral column, bonemarrow, spleen, liver and lymph nodesis typical of canine plasma cell mye-loma (7).

In man, caecal and colonic plas-macytomas are often solitary; dissem-ination, if it occurs, is later in thecourse of the disease (6,8), while skinmasses associated with multiple mye-loma occur when the disease is wellestablished (1).

Until further information is availa-ble about the patterns associated withsolitary plasmacytoma in the dog, anydog having such a tumor should bescreened for evidence of the dissemi-nated disease and a guarded prognosisgiven.

AcknowledgmentsWe would like to thank Dr. Paul

Rumble for his help and for referringthis case to us and Dr. C. Farrow forhis help in radiograph interpretation.

References1. ALBERTS. D.S. and P. LYNCH. Cutaneous

plasmacytomas in myeloma. Archs Der-mat. 114: 1784-1787. 1978.

2. GHADIALLY, F.N., N.R. LOWES and G.M. MES-FIN. Atypical glycogen deposits in a plas-macytoma: an ultrastructural study. J.Path. 122: 157-162. 1977.

3. GILES. R.C.. P. K. HILDEBRANDT and C.A.MONTGOMERY. Carcinoid tumor in the smallintestine of a dog. Vet. Path. 11: 340-349.1974.

4. KOTNER, L.M. and C.C. WANG. Plasmacytomaof the upper air and food passages. Cancer30: 414-418. 1972.

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5. LINGEMAN, D.H. Plasma cell neoplasms ofman and animals. Natn. Cancer Inst. 32:303-310. 1972.

6. NIELSEN, S.M., J.R. SEHENKEN and L.P. CAW-

LEY. Primary colonic plasmacytoma.Cancer 30: 261-266. 1972.

7. OSBORNE, C.A., V. PERMAN, J.H. SAUTIER, J.G.

STEVENS and G.F. HANLON. Multiple mye-loma in the dog. J. Am. vet. med. Ass. 153:1300-1318. 1968.

8. SCHWEERS, C.A., M.T. SHAW, R.E. NORDQUIST,

D.D. ROSE and T. KELL. Solitary cecal plas-macytoma. Cancer 37: 2220-2223. 1976.

9. SORENSON. G.D. Electron microscopicobservations of bone marrow from patientswith multiple myeloma. Lab. Invest. 13:196-213. 1964.

10. UDOJI, w.c. and A.F. FRIGY. Cytoplasmicfibrils in plasma cells of a solitary myeloma.Am. J. clin. Path. 70: 836-840. 1978.

LETTER TO THE EDITOR

A Plea Against Ear CroppingDEAR SIR:With the current local increase in

interest for the showing of dogs, wehave received complaints that certainbreeds of dogs (in particular Boxers,Great Danes and Doberman Pinschers)are still having their ears cropped. Thispractice must surely be deemed inhu-mane as there is absolutely no benefitto the dogs whatsoever. In the past,cropping ears was said to be desirablefor fighting dogs to prevent injuriesand make them appear more fierce,but surely today's society is above allthis.

As the representative for the Cowi-chan and District Branch ofthe BritishColumbia Society for the Preventionof Cruelty to Animals, I am asking youto consider applying pressure togovernments, kennel clubs, breedersand veterinarians to stop this cruel act.Too many puppies are having to sufferthrough the agony of having their earscropped and then taped in all mannerof devices. If you have seen any ofthese poor animals violently shakingtheir heads, scratching and rolling tothe point of tearing their stitches andgetting the surgery infected, you wouldshare our feelings. Acts of this sort forthe sole purpose of the breeders irres-

ponsible whim, should be outlawed.We compel you to please discuss this

with your colleagues and join with usin attempting to ban this barbaricpractice (as has been done in the Uni-ted Kingdom and South Africa).Thank you for your concern.

Yours humanely,

J. ALAN LONGAIR, B.Sc., D.V.M.PresidentCowichan and District Branchof the B. C.S.P. C.A.P. O. Box 843Duncan, British Columbia V9L 3 Y2

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