Pathology of canine bladder and urethral cancer and correlation with tumour progression and survival

J. Comp. Path. 1995 Vol. 113, 113-130

Pathology of Canine Bladder and Urethral Cancer and Correlation with Tumour Progression and Survival V.E. Valli*, A. Norris]', R. M. Jacobs*, E. Laingt, S. Withrow.+, D. Macy~, J. Tomlinson 82 D. McCaw82 G.K. Ogilvie~., G. Pidgeonw and R. A. Hendersonw Departments of*Pathology and 1"ClinicalMedicine, Ontario VeterinaryCollege, Universityof Guelph, Guelph, Ontario, Canada, fComparative Ontology, Collegeof VeterinaryMedicine, Colorado State University, Fort Collins, CO 80523, USA, 82 Medicine, Collegeof VeterinaryMedicine, Universityof Missouri, Columbia, MO 65211, USA, and w Medicine, Collegeof VeterinaryMedicine, Auburn University,Auburn, AL 36849, USA

Summary Biopsy and necropsy specimens, comprising 107 primary carcinomas and three mesenchymal tumours, were reviewed from 110 dogs with cancer of the bladder, urethra, or both. Histological classifications developed for the assessment of human bladder cancer were found to be readily applicable to the dog. These classifications are based on histological features, including the pattern of growth, the cell type, the grade of transitional tumour and the depth of invasion of the bladder wall. Features associated with localized disease in canine transitional cell carcinoma included papillary architecture, "in-situ" tumour, low tumour grade and a strong peritumoral lymphoid cell reaction. Features of tumours with metastasis included infiltrating and non-papillary architecture, increasing tumour grade, depth of invasion, vascular invasion and presence of peritumoral fibrosing reaction. Wide variability was found within single tissue samples, indicating that multiple sample sites are necessary for the adequate characterization of a given lesion. Statistically significant correlations were found between: tumour grade and depth of invasion (P<0"0001); tumour grade and presence of metastases (P<0-029); and peritumoral desmoplasia and metastases (P<0"029). It was concluded that canine bladder cancer could be classified for the purpose of clinical management with a modified World Health Organization system as developed for human tumours. 9 1995 AcademicPress Limited

Introduction Priester a n d M c K a y (1980) reported that of 9891 m a l i g n a n t canine tumours, 134 were of transitional cell type, with 48 occurring in males a n d 86 in females. T h e aetiology of spontaneous bladder cancer in dogs is u n k n o w n ; however, several c o m p o u n d s are capable o f p r o d u c i n g urothelial cancers experimentally, including nitrilotriacetic acid (Anderson a n d Campbell, 1985), cyclophosphamide (Crow et al., 1977; Maxie, 1993), bracken fern (Evans, 00219975/95/060113 + 18 $12.00/0

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1979) and other substances (Pauli et al., 1977). In man, smoking and occupational exposure to aromatic amines in the dye, rubber and coal gas industries increase the risk of bladder cancer (Doll and Peto, 1981). Saccharin will produce the disease in rats, but there is little or no epidemiological evidence that it is a risk factor for man (Arnold et al., 1983). An increased incidence of canine bladder cancer in areas of high industrialization suggests that dogs and man share the same risk factors (Hayes et al., 1981). A number of systems have been devised to classify bladder tumours on the basis of their biological behaviour and thus provide a mechanism for estimating histologically the risk of tumour progression (Mostofi et al., 1986; Pugh, 1973). The four major characteristics that are highly correlated with tumour progression in man are pattern of growth, cell type, degree of differentiation (or tumour grade) and depth of invasion of the bladder wall (Pugh, 1973; Suprun and Bitterman, 1975; Busch et al., 1977; Ooms et al., 1985). In contrast, in the dog, previous work on bladder cancer deals with clinical features (McCaw et al., 1988; Norris et al., 1992), epidemiology (Hayes, 1976; Priester and McKay, 1980) and ultrastructure (Alroy, 1979), rather than with the histological features that are related to clinical progression. The pathology and natural course of transitional tumours and the progression of hyperplasia to neoplasia have been described (Nielsen and Moulton, 1990; Maxie, 1993). The purpose of this investigation was to describe and classify the histological features of canine bladder cancer according to a clinically predictive system of classification for bladder cancer developed for h u m a n tumours (Mostofi et al., 1986). Materials and Methods

Histological slides from 115 dogs with cancer of the bladder, urethra or both were assembled from five Colleges of Veterinary Medicine at the Universities of Auburn (n=9), Colorado State, USA (n=38), Guelph (n=38), Illinois, USA (n=lS) and Missouri, USA (n = 15). The basis for inclusion of cases in the study was a histological diagnosis of bladder or urethral tumour and adequate clinical information. Fortynine dogs received some form of treatment and survival data were available for 98 animals. The histopathological examination was made by one of us (VEV) without reference to the case data. Only haematoxylin and eosin (HE)-stained sections of paraffin wax-embedded tissues were examined. Five of the 115 cases were excluded, leaving 110 in the study. A World Health Organization (WHO) reporting scheme as modified by Mostofi et al. (1986) was used. This included a macroscopical description of the number and size of tissues received and a gross assessment of papillary or flat growth pattern (Table 1), but it deviated from the Mostofi and Weinstein (1986) modified scheme in that, because fresh tissue was not available, the determination of growth pattern was made from macroscopical and microscopical examination of the histological slides. The "number of tissues" was taken as the total number of tissues of lower urinary tract origin on all slides of a given case. For macroscopical description, "size" was the product of length and width of each histological section at its greatest dimensions, measured with a millimetre rule. For tabulation, the area in mm z was recorded from the largest tissue that contained a diagnostically useful lesion. This process assumed that the most prominent lesions had been selected at biopsy or necropsy and had been trimmed for tissue processing in a manner that took account of tumour size and architecture. The criteria for microscopical description were those stated in Table 1.

Canine Bladder and Urethral Cancer

] 15

Table 1 Criteria* for the macroscopieal and microscopical evaluation of bladder and urethral cancer A.

Macroscopical description: 1. N u m b e r of pieces and greatest dimension of each or of the largest piece 2. Configuration: papillary or not

B.

Microscopical description:

e. transitional cell carcinoma and - - s q u a m o u s elements - - g l a n d u l a r elements - - s q u a m o u s and glandular elements f. squamous carcinoma g. adenocarcinoma h. squamous and adenocarcinoma i. undifferentiated carcinoma-I- previous elements

1. Epithelial suoCaces: Intact Desquamated

5. Grade (based on most anaplastic nuclear appearance)

Absent Ulcerated

(WHO):

2. Depth of biopsy:

a. grade 1 b. grade 2 c. grade 3

Turnout (or epithelium) only Lamina propria present Muscularis propria present or absent

6. Extent of infiltration:

3. Patterns of growth (WHO): a. b. c. d. e. f. g. h.

not determinable papillary papillary non-infiltrating CIS non-papillary non-infiltrating CIS papillary infiltrating and non-infiltrating infiltrating and non-infiltrating CIS papillary and infiltrating infiltrating

4. Histology (modified from WHO): a. b. c. d.

transitional cell papilloma transitional cell papilloma, inverted squamous cell papilloma transitional cell carcinoma

a. no invasion ( f l a ~ C I S ) b. no invasion (papillary) c. subepithelial connective tissue (lamina propria) d. muscle 7. Character of invasion: a. broad front (pushing) b. tentacular c. mixed (a and b) d. undetermined 8. Small vessel invasion: a. lymphatic b. blood

* World Health Organization (WHO), modified by Mostofi et al. (1986). CIS = Carcinoma in situ.

Where tumour grade differed in different areas of the same tissue or case, the grade recorded was the highest one observed. In addition, an attempt was made to evaluate the host response to the tumour in terms of desmoplastic reaction as well as lymphoid reaction (none, focal, follicular, diffuse). In cases in which post-mortem sections were available for examination (42), the presence and location of metastases were recorded as well as the presence of second primary tumours arising from other tissues. Microscopical examination was made with a Zeiss Ultraphot II and Technical Pan film. The data were analysed with the NWA Statpak software system (NWA, Portland, OR, USA). Differences between groups were tested by Chi-square analysis. Case data were examined to determine the clinical characteristics, diagnosis and response to treatment. The clinical features of these cases have been reported separately (Norris et al., 1992).

Results T h e n u m b e r o f tissue samples o f b l a d d e r or u r e t h r a l origin e x a m i n e d p e r case v a r i e d f r o m o n e to 11, with 94 o f the 110 a n i m a l s studied p r o v i d i n g o n e to f o u r samples. T h e a r e a o f tissue e x a m i n e d v a r i e d f r o m 2 to 1500 m m 2 with a m e a n o f 1 8 6 m m 2 (i.e., a s p e c i m e n o f a p p r o x i m a t e l y 1"0 • 1"5 cm). I n 71 o f

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V. E. V a l l i e t al. Table 2 G r o w t h p a t t e r n s of 110 c a n i n e t r a n s i t i o n a l b l a d d e r c a r c i n o m a s

Growth pattern Not determinable* Papillary Papillary non-infiltrating CIS Non-papillary non-infiltrating CIS Papillary infiltrating and non-infiltrating Infiltrating and non-infiltrating CIS Papillary and infiltrating Infiltrating Total

Number of cases

Percentage

ll 0 5 3 19 ll 14 47

10 0 4 3 17 l0 13 43

110

100

* Tissue obtained or embedded in such a m a n n e r that the growth pattern was not discernible. CIS = Carcinoma in situ.

the cases the tissue area was 100 m m 2 o r greater, corresponding to a fulldepth sample. The lower urinary tract tissues examined consisted of bladder (89 cases; including, in 29 cases, bladder plus tumour mass), urethra (79 cases), and tumour mass only (seven cases). In this context "mass" refers to an excised portion of exophytic tumour without penetration to the bladder serosa. In one of the seven "mass only" cases, the biopsy did not extend to include the muscularis mucosa of the bladder wall. Tissues were derived by biopsy from 48 dogs, by biopsy on two occasions from three dogs, by biopsy followed by necropsy in 17 dogs, and by necropsy only in 42 dogs (including three with mesenchymal tumours). The female:male ratio was 2:1 and the mean age at the time of diagnosis was 9"4 years. There was no correlation between age, breed, sex or body weight and the response to treatment or the overall survival rate (Norris et al., 1992). O f the 110 dogs, 107 had carcinomas and three had mesenchymal tumours. Both bladder and urethra were tumorous in 60 cases, bladder only in 36, and urethra only in 14. Six dogs died of the disease and three died of other causes, but most were humanely destroyed to minimize suffering.

Macroscopical Description Tumour architecture. In the absence of fresh tissue, papillary architecture was determined macroscopically from the sections by a branched pattern of epithelial growth along fine fibrovascular septa. O f the 107 carcinomas, 72 (65%) had a flat or laminar architecture and 37 (34%) a papillary architecture (Table 2; Fig. 1); insufficient tissue was available for an adequate assessment of this parameter in one dog. Three categories of papilloma (benign) are described in the W H O list of histological diagnoses as applied to man, but in the present series of dogs no lesions that fitted the stated criteria were found. Two lesions were found that fitted the architectural pattern of inverted papillomas. However, cytologically, one had foci of invasion and the other had areas of irregular epithelial thickening with frequent mitoses interpreted to be an in-situ carcinoma (Farrow et al., 1986).

C a n i n e B l a d d e r and U r e t h r a l

9..

Fig. 1.

Cancer

t 17

.....,

Papillary transitional carcinoma. Epithelial fronds branching from a delicate fibrovascular framework. HE. x 20.

Microscopical Description Epithelial surfaces and depth of biopsy. The epithelial surface was intact in 62 (56%) cases, absent due to orientation in embedding in 23 specimens (21%), artefactually lost in handling or desquamated in 20 (18%) and ulcerated and granulating in five (5%). The depth of biopsy included tumour or epithelium only in six (5%) cases and extended to the lamina propria in eight (7%) and to the muscularis in 96 (87%).

Patterns oftumour growth and histology. The patterns of tumour growth are given in Table 2 and carcinoma in situ is illustrated in Fig. 2. The histological types of tumour are given in Table 3, and the subtypes of transitional tumour with squamous or glandular elements are illustrated in Figs 3a and b. The association between tumour grade and histological type is given in Table 4.

Tumourgrade. Grade 1 or well-differentiated transitional cell carcinoma (TCC),

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Fig. 2.

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Carcinoma in situ. Focal thickening of epithelium with nuclear vesiculation, anisokaryosis and irregular crowding. Interepithelial mitoses are present (left of centre and lower right) and vacuolation due to glandular metaplasia. HE. x 300.

present in 24 dogs (22%), was characterized histologically by normal cytoplasmic volume and regularity of nuclear placement. The nuclei were round with mild anisokaryosis and hyperchromicity and nucleoli were small or inapparent (Fig. 4). Grade 2 or moderately differentiated TCC, present in 63 dogs (57%), was characterized by moderate variations in cytoplasmic volume and in nuclear placement, size and shape. The nuclei were hyperchromatic, most having a prominent single nucleolus (Fig. 5). Grade 3 or anaplastic TCC, present in 23 dogs (21%), was characterized by marked variation in cell and nuclear size and shape with irregular nuclear crowding and moulding. The chromatin was deeply stained and irregularly distributed and the nucleoli were prominent, frequently multiple, and variable in location (Fig. 6). The transitional carcinomas and the sub-types (squamous or glandular) contained roughly similar proportions of Grade 2 tumours (59% and 57%, Histological

Table 3 types of canine bladder cancer

Histological ~ype Transitional cell carcinoma (TCC) T C C with squamous or glandular differentiation Adenocarcinoma Undifferentiated carcinoma Mesenchymal tumour Total

Number of cases

Percentage

58 42 6 1 3

53 38 5 1 3

110

100

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Fig. 3.

119

Squamous and glandular metaplasia in transitional tumour. (a) Foci with squamous characteristics. HE. x 270. (b) Papillary frond with multiple areas of cystic pseudoacini. HE. x 100.

respectively; Table 4). However, the sub-types differed from the transitional carcinomas in containing less Grade 1 tumours (14% instead of 26%) and more Grade 3 tumours (29% instead of 15%). This suggests that the sub-types behaved more aggressively. The relationship of histological type of tumour to the presence of metastases is given in Table 5. All cases of T C C without squamous or glandular metaplasia (12) had metastases in those dogs from which necropsy slides were available. However, two dogs with transitional carcinoma and with squamous or glandular metaplasia were apparently free of metastatic disease.

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V.E. Valll e t al.

Fig. 4.

G r a d e 1 or well-differentiated transitional c a r c i n o m a . HE. x 300.

Extent of infiltration. The invasion of normal tissues by tumour was of the "broad front" type in 22 cases (20%; Fig. 7), and tentacular (single cell invasion) in 60 (55%), with tumour cells singly and in rows permeating through the stromal tissues (Fig. 7b). These two patterns of invasion were combined in 11 cases (10%). The pattern was of undetermined type in 17 cases.

Character of invasion. The type of invasion did not appear to affect significantly the occurrence of metastases, although in 37 cases the tentacular and broadfront types of invasion were associated with metastases in 25 and seven cases, respectively (Table 6). Small vessel invasion. Vascular invasion was found in the veins in 15 dogs (14 %), in lymphatics in six (6%), in both sites in one dog and in neither site in 88 Table 4 Association of turnout grade and histological type of canine transitional carcinoma

Grade

Number of cases of stated histological type Transitional cell carcinoma

Transitional, with metaplasia*

Adenocarcinoma

Undifferentiated

Mesenchymal

Total number of cases

1

15

6

0

0

3

2 3

34 9

24 12

5 1

0 1

0 0

24 63 23

Totals

58

42

6

1

3

110

* T r a n s i t i o n a l cell c a r c i n o m a with s q u a m o u s or g l a n d u l a r metaplasia.

C a n i n e B l a d d e r a n d Urethral C a n c e r

Fig. 5.

121

Grade 2 or moderately differentiated transitional carcinoma. HE. x 300.

dogs (80%). There was a tendency for vascular invasion to increase with increasing tumour grade. The proportions of Grade 1, 2 and 3 tumours with vascular invasion were 8%, 20% and 32%, respectively (data not shown). There was an inverse relationship between the histological recognition of tumour emboli and distant metastases. T u m o u r emboli were found in 14 of

Fig. 6.

Grade 3 or poorly differentiated transitional carcinoma. HE. x 300.

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v. v~. Valll et at.

Table 5 Association between histological type of bladder transitional carcinoma and metastases

None

At all sites

Undetermined

Total number of eases

Transitional cell carcinoma TCC with squamous or glandular metaplasia Adenocarcinoma Undifferentiated Mesenchymal

0 2 0 0 0

12 20 5 0 0

46 20 1 1 3

58 42 6 1 3

Totals

2

37

71

110

Histological type

Number of cases with metastases

* "None," indicates that from the 42 dogs from which necropsy slides were available no metastatic disease was detected. "All sites," includes metastases found in all tissues sectioned at necropsy. "Undetermined," includes cases in which no necropsy was carried ont. Thirty-nine (2 + 37) of the 42 dogs from which necropsy slides were available had carcinomas and the remaining three had mesenchymal tumours.

the 37 cases (38%) in which metastases were proved to be present, but emboli were not observed in the remaining 23 (62%).

Tumour grade and tumour spread. T u m o u r grade was examined in relation to depth of invasion, vascular invasion and metastases. "In-situ" lesions were largely of Grade 1 (eight), though some (four) were of Grade 2, but no Grade 3 lesions had an in-situ architecture (Table 7). O f the 37 tumours with papillary architecture, only one was non-invasive and the cell type of this lesion was Grade 1. Lesions of all three grades invaded the muscularis, but the proportion of lesions with deep invasion was greater for Grades 2 and 3 than for Grade 1 (P<0"0001). Invasion was not observed in tissues from 13 dogs (12%), including one case of papillary carcinoma. Invasion extended into the lamina propria in 20 cases (18%) and to or through the muscularis of the bladder in 73 (66%). In four dogs the tissue samples did not permit the evaluation of invasion. Metastases and tumour grade. Since metastases are an unequivocal expression of malignancy, their occurrence was looked for in relation to tumour grade (Table 8). In five of the 21 dogs with Grade 2 T C C the diagnosis was made at necropsy. From two of these five cases samples of tissue other than bladder were available. These samples did not show metastases, but this did not exclude their possible occurrence. All Grade 2 T C C s for which necropsy slides were available were found to have metastasized, whereas two Grade 3 T C C s were not found to have spread to other tissues (P<0-029).

Survival and tumourgrade. Regardless of any treatment given, there was significant correlation between survival and tumour grade (P<0"035) but not between survival and type of invasion or tumour architecture. The survival of dogs with Grade 3 T C C was not significantly different from that of dogs with Grade 2 tumours (Table 9). In contrast, the survival of animals with both Grade 2 and 3 T C C was significantly shorter than that of dogs with Grade 1 tumours (P<0"035). These results demonstrate the significance of an accurate

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Fig. 7.

123

Patterns of invasion. (a) L a m i n a r interface of invasive transitional c a r c i n o m a and muscularis o f b l a d d e r wall. T h e t u m o u r is a d v a n c i n g across a " b r o a d front." HE. x 270. (b) Interface of transitional t u m o u r with a " t e n t a c u l a r " p a t t e r n of invasion of the muscularis of the b l a d d e r wall. HE. x 150.

assessment of tumour grade. Such assessment is complicated by variability of tumour cells within a single lesion, as illustrated in Fig. 8. Host reaction to tumour. Peritumoral desmoplastic reaction evident in HE-stained

sections was present in 41 dogs (38%; Fig. 9) and absent in 69 (63%). Peritumoral sclerosis was not found in two dogs without metastases but was present

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V a l l i e t al.

Table 6 Association between type of invasion of canine transitional carcinoma and presence of metastases

Total number

Number of cases with metastases

Type of invasion None

At all s i t e s

Undetermined (unobserved)

of gases

Broad-front Tentacular Both Undetermined

0 2 0 0

7 25 3 2

15 33 8 15

22 60 11 17

Totals

2

37

71

110

Table 7 Association between tumour grade and depth of invasion of canine transitional carcinoma

Tumour grade

Number of cases with stated @pe of depth of invasion In-situ (no invasion)

1 2 3 Totals

Papillary (non-invasive)

Lamina pwpria

Muscularis

Total number of cases

Undetermined

8 4 0

1 0 0

8 9 3

7 48 18

0 2 2

24 63 23

12

1

20

73

4

110

Table 8 Association between tumour grade of canine transitional carcinoma and presence of metastases

Tumour grade

Number of cases with metastases*

Total number of eases

None

At all s i t e s

Undetermined

1 2 3

0 0 2

0 27 10

24 36 11

24 63 23

Totals

2

37

71

110

* As for Table 5.

Table 9 Association between survival and tumour grade of canine transitional carcinoma

Survival* (months)

Number of cases with tumours of Grade

Total number of Cas#$

<1 1-6 7-12 >12 Totals * Time from diagnosis to death.

1

2

3

7 5 4 2

36 18 3 3

17 1 1 1

60 24 8 6

18

60

20

98

Canine

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Fig. 8.

Variation in tumour grade within a single biopsy. Transitional carcinoma with Grade 2 lesion in the epithelium on the left and Grade 3 turnout on the right. HE. x 230.

Fig. 9.

Host response to tumour invasion. Multiple foci of invasive transitional tumour surrounded by bands of dense, relatively mature connective tissue. HE. x 100.

in 10 cases with metastases. Metastasis occurred in all cases in which sclerosis was present (P<0"029). The lymphoid (cellular) reaction to tumour in the bladder wall was minimal or focal in 57 dogs (52%), follicular in 20 (18%), diffuse in 19 (17%; Fig. 9) and absent in 14 (13%). The benign reactive cells were predominantly small

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V . E . V a U i e t aL

lymphocytes with numerous plasma cells and very few macrophages and granulocytes. A focal lymphocytic infiltration around the neoplasm appeared to be the most common reaction to transitional bladder tumours that metastasized (22 of 37 cases). In two dogs, metastases occurred with no lymphoid reaction to the primary tumour. More extensive follicular and diffuse reactions were associated with a lower proportion of metastatic lesions. The focal, follicular and diffuse types of infiltration became more intense with increasing depth of invasion of the epithelium into the bladder lamina propria and muscularis. Typically, the less invasive lesions (in-situ and papillary) caused less reaction than did the more invasive ones. There appeared to be a reduced lymphoid reaction when sclerosis was particularly prominent; and there was an increased lymphoid inflammatory reaction of focal and follicular but not diffuse type when sclerosis was absent. The spleen was sectioned in 19 of the 42 dogs examined at necropsy; and in these cases, there was significant follicular atrophy in four, periarteriolar sheath atrophy in one, and atrophy of both areas in 14. Metastatic sites and second primary tumours. Metastases were found in 37 of the 42 dogs that were necropsied. The number of cases with metastases in the various tissues were: lung, 18; regional lymph nodes, 15; skeletal muscle, seven; gastrointestinal tract and adrenal gland, five; bone and prostate, four; liver, kidney and urethra, three; bone marrow, pituitary, heart and ureter, two; and thyroid, pancreas, ovary and uterus, one each. Second primary tumours were found in eight of the 107 dogs with carcinoma. These eight included three dogs with benign second primary tumours (Sertoli cell tumour, adrenal cortical adenoma, and pituitary adenoma) and five with malignant second primary tumours (adenocarcinomas of the bile duct, mammary gland, colon, thyroid and lung). Three dogs with primary mesenchymal tumours of the bladder all had leiomyomas and one of these three also had haemangiosarcoma in the heart with widespread metastases. One dog had TCC in both the kidney and the bladder.

Discussion The most significant finding of this study was that bladder cancer in the dog is pathologically very similar to that in man, a finding that validates the application of classifications for human urothelial cancer to canine transitional tumours. Since tumour grade and depth of invasion have the same implications for tumour aggressiveness and progression in dogs as in man, it would appear that transitional tumours in the dog can be diagnosed and managed in a manner similar to that established for man. Pugh (1973), on the proper assessment of tumours of the human bladder, suggested that the pattern of growth, cell type, tumour differentiation (or grade) and depth of invasion all needed to be determined. These criteria would seem readily applicable to the dog and possibly to other animals. The process of management begins with diagnosis, and in that context it is

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surprising that in only 29 0f96 dogs was malignancy detected by urine cytology (Norris et al., 1992). If the surface of the tumour is necrotic or the area in contact with the lumen is small, despite deep or lateral extension, there may be few diagnostic cells in the urine. The process of surgical biopsy must ensure that the tissues obtained are representative of the overall lesion. Since the stage of development of transitional tumours may vary widely in different areas of the same bladder, multiple samples are required to ensure that the lesion is accurately classified. Transitional carcinomas tend to be multifocal and there may be areas of in-situ tumour adjacent to an invasive lesion with a much more aggressive cytological pattern (Fig. 8). A simple diagnosis of transitional tumour is inadequate for the optimal management of this disease, and the pathological description should include tumour architecture, grade and depth of invasion. Superficial or intra-epithelial lesions can be accurately described only if the epithelium is intact, and invasion can be detected only if the biopsy extends to the muscularis. The mucosal surface of the biopsy specimen must not be touched in the fresh state, and touched only carefully in the fixed state if the epithelium is not to be injured or lost. Architecture is an important aspect of interpreting transitional tumours in man and this study demonstrates that in dogs the papillary lesions are less invasive than in man and tend to invade at a later stage of tumour growth. Up to 90% of human transitional tumours have papillary architecture (Koss, 1975). In this study, 38 of the 107 (36 % ) transitional tumours were of papillary type (Table 2). The presence of metastases was undetermined in the five cases of tumour thought to have a papillary-noninfiltrating growth pattern. Metastases were found in eight of 14 cases of papillary infiltrating T C C in contrast to all of 26 flat and infiltrating turnouts examined at necropsy. It is apparent that the architecture of bladder tumours needs more care in recognition and description by veterinarians. It is reported that papillomas constitute approximately 17 % of primary bladder tumours in animals, and in dogs these lesions may undergo malignant transformation (Maxie, 1993). It is not clear why (benign) papillomas were not identified in the present study. The data included primary neoplasms of the lower urinary tract and should have included benign proliferative lesions. The frequency (eight of 14 cases) of metastases associated with the papillary lesions that were examined at necropsy suggests that these lesions were not "overinterpreted". In contrast to animals, in which papillomas of the bladder are a relatively frequent finding, human beings will rarely be found to have papillomas (as distinguished from papillary carcinomas) if strict criteria for their identification are followed (Schreiner and Kissane, 1990). The dog is likely to be similar to man in this respect, and the status of canine lesions previously thought to be benign papillomas should be reviewed. The significance of intra-epithelial lesions such as those that occur in the h u m a n cervix and bronchioles is not well understood in animals and, as a result, in-situ carcinoma is probably underdiagnosed. This may be part of the reason for the apparently greater incidence of papillomas in animals than in man.

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In contrast to traditional views, it would appear that a vigorous desmoplastic reaction is not so much a function of a "walling-oiF' of tumour by the host but a tumour-regulated response that may protect the neoplasm from the host's cellular and soluble immune defences (MartinezoHernandez, 1988). Tumours with scanty stroma (carcinomas) tend to differ from those in which the stroma is plentiful by their greater content of inflammatory cells (MartinezHernandez, 1988). In the light of this finding it was remarkable that in the present study there were two cases in which both peri-tumoral sclerosis and metastases were absent, but that in all cases in which sclerosis was a prominent feature of the lesion there were concurrent metastases. More important, metastases were present in more than twice as many cases when sclerosis was present than when it was absent (10 of 27 cases). These apparent trends might have been reinforced had it been possible to quantify the host desmoplastic reaction by reticulin or collagen stains. The same overall proportion of inflammatory reaction was found in cases with peritumoral sclerosis (60 of 69 cases; 87%) as compared with cases without sclerosis (36 of 41; 88%), although focal and follicular reactions were more common when sclerosis was absent. Tumour-infiltrating lymphocytes are likely to be thymic-derived and aggregated in a diffuse manner. In this study, the administration of chemotherapeutic agents may have been a confounding factor in the evaluation of host cellular immune response. The intensity of the inflammatory reaction decreased as the depth of invasion of the bladder wall increased and fewer metastases were found as the lymphoid reaction became more intense (data not shown). It is not clear why there should be fewer cases with metastases when there is no apparent lymphoid response. Perhaps both the reduced inflammatory reaction and absence of metastasis are due to the effects of therapy. In human bladder cancer the prognosis improves with increasing intensity of reaction by tumour-infiltrating lymphocytes (Tsujihashi et al., 1989). In both human and canine bladder cancer the lymphocytic reaction occurs around the tumour foci and relatively few lymphocytes penetrate between the individual tumour cells. The association between peritumoral lymphoid reaction and sclerosis may not be a chance occurrence. Post-incisional fibroplasia in nude mice was found to exceed the rate of wound repair in normal control animals and reconstitution of the deficient animals with T cells decreased their collagen production to basal rates (Barbul et al., 1989). It was concluded that T lymphocytes played an early stimulating and a late inhibiting role in wound repair. Thus, exuberant peritumoral sclerosis may represent an "early" ineffective host response and minimal reaction a more effective and mature T-cell reactivity. In the present study, the tendency for the cellular infiltrate and peritumoral fibrosis to have an inverse relationship lends support to the view that tumour-associated desmoplasia benefits the neoplasm, but the cellular reaction benefits the host. When diagnostic surgery was carried out, many of the cases appeared to have extensive tumour formation at the primary site. There is little doubt that in many of these animals dissemination was a relatively late event and therefore

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earlier detection would have increased the number that could have been saved by surgical intervention. Acknowledgments

We thank the staff members in the various institutions for assistance with assembly of the case records and histological slides, andJoyce Amacher for clerical assistance. References

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Received, September 14th, 19941 Accepted, March 3rd, 1995 J