Veterinary Pathology OnlineFirst, published on July 24, 2014 as doi:10.1177/0300985814543198
Full Length Manuscript
Prognostic Value of Histologic Grading for Feline Mammary Carcinoma: A Retrospective Survival Analysis
Veterinary Pathology 1-12 ª The Author(s) 2014 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/0300985814543198 vet.sagepub.com
S. W. Mills1*, K. M. Musil1*, J. L. Davies2, S. Hendrick1, C. Duncan3, M. L. Jackson1, B. Kidney1, H. Philibert1, B. K. Wobeser1, and E. Simko1
Abstract Feline mammary carcinoma is highly malignant and generally associated with a poor prognosis, although studies suggest the range of survival times in affected cats is broad. Histologic grading of these tumors is achieved using the Elston and Ellis system, originally developed for human breast cancer. In cats, however, classification using this method has variable prognostic value. Therefore, objectives of this study were (1) to evaluate the Elston and Ellis grading system for feline mammary carcinoma in a predominantly spayed population and (2) to determine whether modification of this system or development of a novel system improved the prognostic value of histologic grading. Survey data and histologic features for 108 carcinomas from 97 cats were analyzed with respect to overall survival. Elston and Ellis grading failed to correlate significantly with overall survival. Using multivariable analysis, lymphovascular invasion, nuclear form, and mitotic count each demonstrated independent prognostic significance (P ¼ .008, 25% abnormal) were then assigned. Mitotic figures were evaluated according to Elston and Ellis.8 Briefly, mitotic figures were counted in 10 consecutive fields at the periphery of the tumor in the areas of highest proliferative activity. Microscope field diameter was maintained at 0.53 mm for all observations to standardize counts.1 Care was taken to exclude apoptotic, pyknotic, or otherwise hyperchromatic nuclei, only including those that had definitively entered prophase or were in metaphase, anaphase, or telophase. In certain cases where tumor heterogeneity and high mitotic rate caused mitotic count to differ by more than 20% between 2 observers, they were repeated independently until acceptable concordance was attained. A correlation coefficient (Pearson’s R value) of 0.954 was obtained overall.
Histologic Grading Initially, tumors were graded according to the EE grading system described for human breast cancer (Table 1).8 In this system, carcinomas are scored according to 3 criteria: percentage tubule formation, degree of nuclear pleomorphism, and mitotic count. Briefly, the degree of tubule formation is assessed subjectively on low power and expressed as a percentage. When greater than 75% of the tumor parenchyma exhibits tubule formation, 1 point is assigned. Tubule formation between 10% and 75% is given a score of 2 points, and 3 points are assigned when 17 was given 3 points. The score for each category was summed, and the total score for each tumor corresponded to a predetermined grade (I, II, or III), indicating well-differentiated, moderately differentiated, or poorly differentiated carcinomas, respectively. Three new grading systems were designed, applied to our data, and analyzed with respect to OS. First, in the mitoticmodified Elston and Ellis (MMEE) grading system (Table 1), range subcategories within the mitotic count category of the EE grading system were modified to better accommodate the wide range and high magnitude of mitotic counts observed within the tumors we evaluated. Cutoff values between mitotic
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Veterinary Pathology
Figures 1–4. Mammary gland; cat, mammary carcinoma. Hematoxylin and eosin. Figure 1. Example of low nuclear form score (5% abnormal). Figure 2. Higher magnification of Fig. 1. Figure 3. Example of high nuclear form score (>25% abnormally shaped nuclei). Figure 4. Higher magnification of Fig. 3. Examples of abnormal nuclear form are frequently noted (eg, deviations from a smooth nuclear contour and round or oval shape such as corrugation, angularity, clefting, indentation, or overtly ameboid shape; arrowheads).
count subcategories were derived directly from tertile boundaries from our results. Next, with the revised Elston and Ellis (REE) grading system (Table 1), the EE grading system was modified further to include nuclear form scoring and lymphovascular invasion. Nuclear pleomorphism scoring was removed, and an additional point was added to the grading chart to accommodate the addition of lymphovascular invasion. Scoring and grading with the MMEE and REE grading systems was otherwise achieved in the same manner as described above for EE grading. Finally, a novel grading system was developed directly from the Cox proportional hazards analysis (Table 2). Hazard ratios were assigned to the presence of the independent prognostic factors (lymphovascular invasion, nuclear form, and mitotic count) using coefficients from the model and divided into grades. Mitotic count subcategories were derived directly from the median mitotic count observed in our results. Using the novel grading system, the absence of lymphovascular
invasion together with less than or equal to 5% abnormal nuclear form and a mitotic count less than or equal to 62 in 10 high-power fields corresponded to grade I (low-grade carcinoma). The presence of any one of lymphovascular invasion, greater than 5% abnormal nuclear form, or a cumulative mitotic count greater than 62 yielded grade II (intermediate-grade carcinoma). Finally, if any 2 or all 3 of the aforementioned features were present, grade III (high-grade carcinoma) was assigned.
Statistical Analysis Analyses were conducted using Prism (GraphPad Software, La Jolla, CA) and Stata (StataCorp LP, College Station TX) statistical software packages. Normality was assessed with the D’Agostino and Pearson normality test. To analyze the relationship between individual survey or histologic criteria/
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Mills et al
5
Table 1. Elston and Ellis (EE), Mitotic-Modified Elston and Ellis (MMEE), and Revised Elston and Ellis (REE) Grading Systems for Evaluation of Invasive Mammary Carcinoma in Female Cats. Applicable Grading System EE, MMEE, REE
EE, MMEE
EE, MMEE, REE
REE only
REE only
Histologic Feature Tubule formation Comprises a majority of the tumor (>75%) Present to a moderate degree (10%–75%) Little or none present (25% abnormal
Point Total
Grade
Comment
3-5 6-7 8-9 or 8-10 (REE)
I II III
Well differentiated Moderately differentiated Poorly differentiated
Score 1 2 3 1 2 3
1 2 3 0 1 1 2 3
a
Cumulative number of mitoses in 10 consecutive fields in the most mitotically active area with a microscope field diameter of 0.53 mm (40 objective). Abnormal nuclear form includes any deviation from smooth nuclear contour or round/oval nuclear shape such as clefting, angularity, corrugation, or ameboid morphology assessed at high power (40–60 objective) in the least differentiated and/or most invasive portions of the tumor (Figs. 1–4). The number of nuclei exhibiting the abnormal nuclear form is estimated and expressed as a percentage of the total number of nuclei within any given field. b
grading and OS, Kaplan-Meier curves were generated and compared using log rank or Gehan-Breslow-Wilcoxon tests. A Cox proportional hazards model was used to evaluate the effect of multiple criteria on OS, and hazard ratios were calculated using the Mantel-Haenszel method. For continuous variables, categorization was based on median values or tertiles unless otherwise stated. OS was defined as the period between the date of biopsy/excision and the date of death or last documented follow-up. Cases were grouped into 5 distinct outcomes: (1) alive, (2) lost to follow-up, (3) tumor-related death/euthanasia, (4) non–tumor-related death/euthanasia, and (5) death/euthanasia of unverified cause (but suspected to be tumor related). For statistical analysis of OS, outcomes 1, 2, and 4 were considered censored events. In all cases, a P value equal to or less than .05 was considered significant.
Results Female cats in this study ranged in age from 3.5 to 20 years old (median, 11 years; mean [SD], 11.4 [3.5] years). Breeds included 65 domestic short hair (66.3%), 14 domestic long hair (14.4%), 5 domestic medium hair (5.1%), 6 Siamese (and crosses) (6.2%), 2 Maine Coon (and crosses) (2%), 1 Korat cross (1%), 1 Manx (1%), 1 Birman (1%), 1 Chinchilla (1%),
and 1 Devon Rex (1%). Ovariectomy or ovariohysterectomy (spaying) had been performed previously in 82 cats (84.7%), while 15 (15.3%) were intact or spayed concurrently with mass removal. Tumor diameter was less than 2 cm in 51 cases (52.6%), between 2 and 3 cm in 18 cases (18.4%), greater than 3 cm in 19 cases (19.6%), and unknown in 9 cases (9.2%). On presentation to the referring clinic, 56 cats (57.7%) were reported to have a single mass, 40 (40.8%) had multiple masses, and the number of masses was unreported in 1. A total of 43 cases (43.9%) were classified as WHO stage 1, 15 (15.3%) as stage 2, and 32 (33%) as stage 3, with 7 (7.2%) unknown (survey information incomplete). Results of Kaplan-Meier survival analysis of survey data and histologic features are listed in Tables 3, 4, and 5. Although tumor diameter was not a significant factor overall, those greater than 3 cm in diameter were associated with reduced OS (P ¼ .046) compared with tumors less than 2 cm in diameter. More advanced WHO stage and the presence of lymph node metastases also showed statistically significant negative correlation with OS (both P ¼ .01). Both WHO histologic subtype (P ¼ .005) and the presence of lymphovascular invasion (P < .001) corresponded with OS. A weak association was found between tumors with >75% tubule formation and those with less than 10% tubule formation (P ¼ .037) and OS, the
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Veterinary Pathology
Table 2. Novel Grading System for Evaluation of Invasive Mammary Carcinoma in Female Cats. Histologic Featurea
Score
Lymphovascular invasion Absent Present Nuclear formb 5% abnormal >5% abnormal Mitotic countc 62 >62
0 1 0 1 0 1
Total Score
Grade
0 1 2–3
I (low-grade carcinoma) II (intermediate-grade carcinoma) III (high-grade carcinoma)
Median Survival, mo
Survival at 18 mo, %
31 14 8
82 37 18
a
Each feature is evaluated and scores are assigned and summed. Absence of lymphovascular invasion, abnormal nuclear form 5%, and a mitotic count 62 correspond to grade I (total score ¼ 0). The presence of any one of lymphovascular invasion, abnormal nuclear form >5%, or a mitotic count >62 indicates grade II (total score ¼ 1). If any 2 or all 3 features are present, grade III is assigned (total score ¼ 2–3). b Abnormal nuclear form includes any deviation from smooth nuclear contour or round/oval nuclear shape such as clefting, angularity, corrugation, or ameboid morphology assessed at high power (40–60 objective) in the least differentiated and/or most invasive portions of the tumor (Figs. 1–4). The number of nuclei exhibiting the abnormal nuclear form is estimated and expressed as a percentage of the total number of nuclei within any given field. c Cumulative number of mitoses in 10 consecutive fields in the most mitotically active area with a microscope field diameter of 0.53 mm (40 objective).
Table 3. Kaplan-Meier Analysis of Selected Clinicopathologic Criteria With Respect to Overall Survival in Female Cats With Mammary Carcinoma. na (Median Survival in mo) Age (median, 11 y) (i) 11 y (ii) > 11 y Reproductive status (i) Intact (ii) Spayed Tumor diameter (i) 3 cm Lymph node metastases (i) No (ii) Yes WHO stage (i) 1 (ii) 2 (iii) 3
50 (15) 47 (14) 15 (11) 82 (15) 51 (16) 18 (14) 19 (11) 66 (16) 17 (9) 43 (18) 15 (15) 32 (10)
P Value
Hazard Ratio
95% CI
.9 — — .2 — — .09 .17b .49c .046d .01 — — .01 .19b .20c .004d
1 — — 1.5 — —
0.66–1.6 — — 0.8–2.9 — —
0.65b 0.78c 0.50d 0.39 — —
0.35–1.2 0.38–1.6 0.25–1.0 0.19–0.8 — —
0.63b 0.66c 0.43d
0.31–1.3 0.35–1.3 0.25–0.7
CI, confidence interval; WHO, World Health Organization; —, . a Number of cats for which survey data were available. b i vs ii. c ii vs iii. d i vs iii.
latter conferring a poorer prognosis. The median survival of cats with solid or cribriform carcinomas (10 and 8 months, respectively) was less than half that of cats with the tubulopapillary subtype (21 months). Percentage of necrosis, the presence or nature of any inflammation, the stromal response, and the percentage of squamous differentiation were not statistically significant with respect to OS. In contrast, with the exception of chromatin vesiculation, all nuclear characteristics
evaluated within the neoplastic population were significantly and inversely related to OS, including abnormal nucleolar morphology (P ¼ .013), increased anisokaryosis (P ¼ .013), increased size (P ¼ .038), abnormal nuclear form (P < .001), increased nuclear pleomorphism score (P ¼ .006), and increased mitotic count (P ¼ .021). Visible nucleoli were absent in only 2 tumors (1.9%); nuclear size was increased relative to normal in 104 tumors (96.3%). The mean mitotic count
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Table 4. Kaplan-Meier Analysis of Low-Power Histologic Criteria With Respect to Overall Survival in Female Cats With Mammary Carcinoma. na (Median Survival in mo) Tumor subtype (i) Tubulopapillary (ii) Solid (iii) Cribriform (iv) Squamous cell carcinoma Tubule formatione (i) 75% Necrosis (i) 25% (ii) >25% Inflammation (i) None present or mild (ii) Lymphoplasmacytic (iii) Neutrophilic or pleocellular Lymphovascular invasion (i) Absent (ii) Present Stromal response (i) Normal (mild-moderate) (ii) Marked (iii) Intratumoral Squamous differentiation (i) 5% (ii) >5%
61 (21) 36 (10) 10 (8) 1 (—) 37 (13) 54 (14) 17 (29) 56 (18) 52 (12) 34 (18) 59 (15) 15 (9) 68 (18) 40 (8) 71 (14) 29 (14) 8 (31) 67 (15) 41 (12)
P Value .005 25% abnormal Nuclear pleomorphism scoree (i) 1 (ii) 2 (iii) 3 Mitotic countf (median, 62) (i) 62 (ii) >62
71 (13) 34 (15) 3 (18) 2 (34) 96 (15) 10 (4) 69 (18) 35 (9) 4 (14) 4 (35) 89 (14) 15 (16) 64 (21) 36 (12) 8 (12) 2 (34) 83 (16) 23 (11) 54 (18) 54 (9)
P Value .96 .99b .71c .84d .013 .58b .004c .43d .013 .048b .8c .18d .038 .027b .35c .002d
Full Length Manuscript
Prognostic Value of Histologic Grading for Feline Mammary Carcinoma: A Retrospective Survival Analysis
Veterinary Pathology 1-12 ª The Author(s) 2014 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/0300985814543198 vet.sagepub.com
S. W. Mills1*, K. M. Musil1*, J. L. Davies2, S. Hendrick1, C. Duncan3, M. L. Jackson1, B. Kidney1, H. Philibert1, B. K. Wobeser1, and E. Simko1
Abstract Feline mammary carcinoma is highly malignant and generally associated with a poor prognosis, although studies suggest the range of survival times in affected cats is broad. Histologic grading of these tumors is achieved using the Elston and Ellis system, originally developed for human breast cancer. In cats, however, classification using this method has variable prognostic value. Therefore, objectives of this study were (1) to evaluate the Elston and Ellis grading system for feline mammary carcinoma in a predominantly spayed population and (2) to determine whether modification of this system or development of a novel system improved the prognostic value of histologic grading. Survey data and histologic features for 108 carcinomas from 97 cats were analyzed with respect to overall survival. Elston and Ellis grading failed to correlate significantly with overall survival. Using multivariable analysis, lymphovascular invasion, nuclear form, and mitotic count each demonstrated independent prognostic significance (P ¼ .008, 25% abnormal) were then assigned. Mitotic figures were evaluated according to Elston and Ellis.8 Briefly, mitotic figures were counted in 10 consecutive fields at the periphery of the tumor in the areas of highest proliferative activity. Microscope field diameter was maintained at 0.53 mm for all observations to standardize counts.1 Care was taken to exclude apoptotic, pyknotic, or otherwise hyperchromatic nuclei, only including those that had definitively entered prophase or were in metaphase, anaphase, or telophase. In certain cases where tumor heterogeneity and high mitotic rate caused mitotic count to differ by more than 20% between 2 observers, they were repeated independently until acceptable concordance was attained. A correlation coefficient (Pearson’s R value) of 0.954 was obtained overall.
Histologic Grading Initially, tumors were graded according to the EE grading system described for human breast cancer (Table 1).8 In this system, carcinomas are scored according to 3 criteria: percentage tubule formation, degree of nuclear pleomorphism, and mitotic count. Briefly, the degree of tubule formation is assessed subjectively on low power and expressed as a percentage. When greater than 75% of the tumor parenchyma exhibits tubule formation, 1 point is assigned. Tubule formation between 10% and 75% is given a score of 2 points, and 3 points are assigned when 17 was given 3 points. The score for each category was summed, and the total score for each tumor corresponded to a predetermined grade (I, II, or III), indicating well-differentiated, moderately differentiated, or poorly differentiated carcinomas, respectively. Three new grading systems were designed, applied to our data, and analyzed with respect to OS. First, in the mitoticmodified Elston and Ellis (MMEE) grading system (Table 1), range subcategories within the mitotic count category of the EE grading system were modified to better accommodate the wide range and high magnitude of mitotic counts observed within the tumors we evaluated. Cutoff values between mitotic
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Veterinary Pathology
Figures 1–4. Mammary gland; cat, mammary carcinoma. Hematoxylin and eosin. Figure 1. Example of low nuclear form score (5% abnormal). Figure 2. Higher magnification of Fig. 1. Figure 3. Example of high nuclear form score (>25% abnormally shaped nuclei). Figure 4. Higher magnification of Fig. 3. Examples of abnormal nuclear form are frequently noted (eg, deviations from a smooth nuclear contour and round or oval shape such as corrugation, angularity, clefting, indentation, or overtly ameboid shape; arrowheads).
count subcategories were derived directly from tertile boundaries from our results. Next, with the revised Elston and Ellis (REE) grading system (Table 1), the EE grading system was modified further to include nuclear form scoring and lymphovascular invasion. Nuclear pleomorphism scoring was removed, and an additional point was added to the grading chart to accommodate the addition of lymphovascular invasion. Scoring and grading with the MMEE and REE grading systems was otherwise achieved in the same manner as described above for EE grading. Finally, a novel grading system was developed directly from the Cox proportional hazards analysis (Table 2). Hazard ratios were assigned to the presence of the independent prognostic factors (lymphovascular invasion, nuclear form, and mitotic count) using coefficients from the model and divided into grades. Mitotic count subcategories were derived directly from the median mitotic count observed in our results. Using the novel grading system, the absence of lymphovascular
invasion together with less than or equal to 5% abnormal nuclear form and a mitotic count less than or equal to 62 in 10 high-power fields corresponded to grade I (low-grade carcinoma). The presence of any one of lymphovascular invasion, greater than 5% abnormal nuclear form, or a cumulative mitotic count greater than 62 yielded grade II (intermediate-grade carcinoma). Finally, if any 2 or all 3 of the aforementioned features were present, grade III (high-grade carcinoma) was assigned.
Statistical Analysis Analyses were conducted using Prism (GraphPad Software, La Jolla, CA) and Stata (StataCorp LP, College Station TX) statistical software packages. Normality was assessed with the D’Agostino and Pearson normality test. To analyze the relationship between individual survey or histologic criteria/
Downloaded from vet.sagepub.com at MEMORIAL UNIV OF NEWFOUNDLAND on January 30, 2015
Mills et al
5
Table 1. Elston and Ellis (EE), Mitotic-Modified Elston and Ellis (MMEE), and Revised Elston and Ellis (REE) Grading Systems for Evaluation of Invasive Mammary Carcinoma in Female Cats. Applicable Grading System EE, MMEE, REE
EE, MMEE
EE, MMEE, REE
REE only
REE only
Histologic Feature Tubule formation Comprises a majority of the tumor (>75%) Present to a moderate degree (10%–75%) Little or none present (25% abnormal
Point Total
Grade
Comment
3-5 6-7 8-9 or 8-10 (REE)
I II III
Well differentiated Moderately differentiated Poorly differentiated
Score 1 2 3 1 2 3
1 2 3 0 1 1 2 3
a
Cumulative number of mitoses in 10 consecutive fields in the most mitotically active area with a microscope field diameter of 0.53 mm (40 objective). Abnormal nuclear form includes any deviation from smooth nuclear contour or round/oval nuclear shape such as clefting, angularity, corrugation, or ameboid morphology assessed at high power (40–60 objective) in the least differentiated and/or most invasive portions of the tumor (Figs. 1–4). The number of nuclei exhibiting the abnormal nuclear form is estimated and expressed as a percentage of the total number of nuclei within any given field. b
grading and OS, Kaplan-Meier curves were generated and compared using log rank or Gehan-Breslow-Wilcoxon tests. A Cox proportional hazards model was used to evaluate the effect of multiple criteria on OS, and hazard ratios were calculated using the Mantel-Haenszel method. For continuous variables, categorization was based on median values or tertiles unless otherwise stated. OS was defined as the period between the date of biopsy/excision and the date of death or last documented follow-up. Cases were grouped into 5 distinct outcomes: (1) alive, (2) lost to follow-up, (3) tumor-related death/euthanasia, (4) non–tumor-related death/euthanasia, and (5) death/euthanasia of unverified cause (but suspected to be tumor related). For statistical analysis of OS, outcomes 1, 2, and 4 were considered censored events. In all cases, a P value equal to or less than .05 was considered significant.
Results Female cats in this study ranged in age from 3.5 to 20 years old (median, 11 years; mean [SD], 11.4 [3.5] years). Breeds included 65 domestic short hair (66.3%), 14 domestic long hair (14.4%), 5 domestic medium hair (5.1%), 6 Siamese (and crosses) (6.2%), 2 Maine Coon (and crosses) (2%), 1 Korat cross (1%), 1 Manx (1%), 1 Birman (1%), 1 Chinchilla (1%),
and 1 Devon Rex (1%). Ovariectomy or ovariohysterectomy (spaying) had been performed previously in 82 cats (84.7%), while 15 (15.3%) were intact or spayed concurrently with mass removal. Tumor diameter was less than 2 cm in 51 cases (52.6%), between 2 and 3 cm in 18 cases (18.4%), greater than 3 cm in 19 cases (19.6%), and unknown in 9 cases (9.2%). On presentation to the referring clinic, 56 cats (57.7%) were reported to have a single mass, 40 (40.8%) had multiple masses, and the number of masses was unreported in 1. A total of 43 cases (43.9%) were classified as WHO stage 1, 15 (15.3%) as stage 2, and 32 (33%) as stage 3, with 7 (7.2%) unknown (survey information incomplete). Results of Kaplan-Meier survival analysis of survey data and histologic features are listed in Tables 3, 4, and 5. Although tumor diameter was not a significant factor overall, those greater than 3 cm in diameter were associated with reduced OS (P ¼ .046) compared with tumors less than 2 cm in diameter. More advanced WHO stage and the presence of lymph node metastases also showed statistically significant negative correlation with OS (both P ¼ .01). Both WHO histologic subtype (P ¼ .005) and the presence of lymphovascular invasion (P < .001) corresponded with OS. A weak association was found between tumors with >75% tubule formation and those with less than 10% tubule formation (P ¼ .037) and OS, the
Downloaded from vet.sagepub.com at MEMORIAL UNIV OF NEWFOUNDLAND on January 30, 2015
6
Veterinary Pathology
Table 2. Novel Grading System for Evaluation of Invasive Mammary Carcinoma in Female Cats. Histologic Featurea
Score
Lymphovascular invasion Absent Present Nuclear formb 5% abnormal >5% abnormal Mitotic countc 62 >62
0 1 0 1 0 1
Total Score
Grade
0 1 2–3
I (low-grade carcinoma) II (intermediate-grade carcinoma) III (high-grade carcinoma)
Median Survival, mo
Survival at 18 mo, %
31 14 8
82 37 18
a
Each feature is evaluated and scores are assigned and summed. Absence of lymphovascular invasion, abnormal nuclear form 5%, and a mitotic count 62 correspond to grade I (total score ¼ 0). The presence of any one of lymphovascular invasion, abnormal nuclear form >5%, or a mitotic count >62 indicates grade II (total score ¼ 1). If any 2 or all 3 features are present, grade III is assigned (total score ¼ 2–3). b Abnormal nuclear form includes any deviation from smooth nuclear contour or round/oval nuclear shape such as clefting, angularity, corrugation, or ameboid morphology assessed at high power (40–60 objective) in the least differentiated and/or most invasive portions of the tumor (Figs. 1–4). The number of nuclei exhibiting the abnormal nuclear form is estimated and expressed as a percentage of the total number of nuclei within any given field. c Cumulative number of mitoses in 10 consecutive fields in the most mitotically active area with a microscope field diameter of 0.53 mm (40 objective).
Table 3. Kaplan-Meier Analysis of Selected Clinicopathologic Criteria With Respect to Overall Survival in Female Cats With Mammary Carcinoma. na (Median Survival in mo) Age (median, 11 y) (i) 11 y (ii) > 11 y Reproductive status (i) Intact (ii) Spayed Tumor diameter (i) 3 cm Lymph node metastases (i) No (ii) Yes WHO stage (i) 1 (ii) 2 (iii) 3
50 (15) 47 (14) 15 (11) 82 (15) 51 (16) 18 (14) 19 (11) 66 (16) 17 (9) 43 (18) 15 (15) 32 (10)
P Value
Hazard Ratio
95% CI
.9 — — .2 — — .09 .17b .49c .046d .01 — — .01 .19b .20c .004d
1 — — 1.5 — —
0.66–1.6 — — 0.8–2.9 — —
0.65b 0.78c 0.50d 0.39 — —
0.35–1.2 0.38–1.6 0.25–1.0 0.19–0.8 — —
0.63b 0.66c 0.43d
0.31–1.3 0.35–1.3 0.25–0.7
CI, confidence interval; WHO, World Health Organization; —, . a Number of cats for which survey data were available. b i vs ii. c ii vs iii. d i vs iii.
latter conferring a poorer prognosis. The median survival of cats with solid or cribriform carcinomas (10 and 8 months, respectively) was less than half that of cats with the tubulopapillary subtype (21 months). Percentage of necrosis, the presence or nature of any inflammation, the stromal response, and the percentage of squamous differentiation were not statistically significant with respect to OS. In contrast, with the exception of chromatin vesiculation, all nuclear characteristics
evaluated within the neoplastic population were significantly and inversely related to OS, including abnormal nucleolar morphology (P ¼ .013), increased anisokaryosis (P ¼ .013), increased size (P ¼ .038), abnormal nuclear form (P < .001), increased nuclear pleomorphism score (P ¼ .006), and increased mitotic count (P ¼ .021). Visible nucleoli were absent in only 2 tumors (1.9%); nuclear size was increased relative to normal in 104 tumors (96.3%). The mean mitotic count
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Mills et al
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Table 4. Kaplan-Meier Analysis of Low-Power Histologic Criteria With Respect to Overall Survival in Female Cats With Mammary Carcinoma. na (Median Survival in mo) Tumor subtype (i) Tubulopapillary (ii) Solid (iii) Cribriform (iv) Squamous cell carcinoma Tubule formatione (i) 75% Necrosis (i) 25% (ii) >25% Inflammation (i) None present or mild (ii) Lymphoplasmacytic (iii) Neutrophilic or pleocellular Lymphovascular invasion (i) Absent (ii) Present Stromal response (i) Normal (mild-moderate) (ii) Marked (iii) Intratumoral Squamous differentiation (i) 5% (ii) >5%
61 (21) 36 (10) 10 (8) 1 (—) 37 (13) 54 (14) 17 (29) 56 (18) 52 (12) 34 (18) 59 (15) 15 (9) 68 (18) 40 (8) 71 (14) 29 (14) 8 (31) 67 (15) 41 (12)
P Value .005 25% abnormal Nuclear pleomorphism scoree (i) 1 (ii) 2 (iii) 3 Mitotic countf (median, 62) (i) 62 (ii) >62
71 (13) 34 (15) 3 (18) 2 (34) 96 (15) 10 (4) 69 (18) 35 (9) 4 (14) 4 (35) 89 (14) 15 (16) 64 (21) 36 (12) 8 (12) 2 (34) 83 (16) 23 (11) 54 (18) 54 (9)
P Value .96 .99b .71c .84d .013 .58b .004c .43d .013 .048b .8c .18d .038 .027b .35c .002d
