Objective—To characterize variability in melanoma-associated antigen (MAA) genes and gene expression in melanomas of dogs.
Animals—18 dogs with malignant melanomas and 8 healthy control dogs.
Procedures—cDNA was prepared from malignant melanoma biopsy specimens and from pigmented oral mucocutaneous tissues of healthy control dogs. Genomic DNA was extracted from poorly pigmented melanomas. A PCR assay was performed by use of Melan-A, SILV, or tyrosinase-specific primers.
Results—Splice variants of Melan-A and SILV were identified in malignant melanomas and also in healthy pigmented tissues, whereas a tyrosinase splice variant was detected in melanoma tissues only. A short interspersed nuclear element (SINE) insertion mutation was identified in the SILV gene in 1 of 10 poorly pigmented melanomas. Six novel exonic single nucleotide polymorphisms (SNPs; 3 synonymous and 3 nonsynonymous) were detected in the tyrosinase gene, and 1 nonsynonymous exonic SNP was detected in the SILV gene.
Conclusions and Clinical Relevance—Variants of MAA mRNA were detected in malignant melanoma tissues of dogs. The importance of MAA alternative transcripts expressed in melanomas and normal pigmented tissues was unclear, but they may have represented a means of regulating melanin synthesis. The tyrosinase splice variant was detected only in melanomas and could potentially be a tumor-specific target for immunotherapy. A SILV SINE insertion mutation was identified in a melanoma from a Great Dane, a breed known to carry this mutation (associated with merle coat color). The nonsynonymous SNPs detected in tyrosinase and SILV transcripts did not appear to affect tumor pigmentation.
Objective—To compare treatment protocols for chronic enteropathy and concurrent protein-losing enteropathy that used prednisolone in conjunction with either azathioprine or chlorambucil in dogs.
Design—Retrospective case series.
Procedures—All dogs had hypoalbuminemia (serum albumin concentration, < 18.0 g/L) and chronic enteropathy as diagnosed via complete gastrointestinal tract investigations including intestinal biopsy. Dogs received either an azathioprine-prednisolone combination (group A; n = 13) or a chlorambucil-prednisolone combination (group C; 14). Response to treatment was assessed by evaluation of body weight gain, serum albumin concentration, and duration of primary treatment.
Results—No significant pretreatment differences were detected between groups for any baseline variable (signalment and weight), clinicopathologic variable (albumin, cobalamin, and folate concentrations), or histopathologic findings. After treatment, serum albumin concentration and weight gain were significantly greater in group C. Median survival time for group A dogs was 30 days (95% confidence interval, 15 to 45 days) and was not reached for group C dogs. Duration of primary treatment was positively associated with the histopathologic presence of mild lacteal dilatation and use of a chlorambucil-prednisolone combination.
Conclusions and Clinical Relevance—Results suggested that a chlorambucil-prednisolone protocol is more efficacious for treatment of chronic enteropathy and concurrent protein-losing enteropathy, compared with an azathioprine-prednisolone combination. Given these findings, a prospective randomized clinical trial is warranted.
Objective—To determine whether argyrophilic nucleolar organizing regions (AgNORs), Ki-67, and proliferating cell nuclear antigen (PCNA) scores were associated with histologic grade and survival in dogs with soft tissue sarcomas (STSs).
Animals—60 dogs with STSs.
Procedure—Medical records were examined and histologic specimens were reviewed. Tissue specimens obtained from archival materials were used to prepare sections for histologic staining for AgNOR and immunohistochemical staining for Ki-67 and PCNA labeling. Follow-up monitoring was obtained by reevaluation or telephone conversations with referring veterinarians or owners.
Results—27 (45%) STSs were grade 1, 23 (38%) were grade 2, and 10 (17%) were grade 3. The mean and median AgNOR, Ki-67, and PCNA scores were determined, and significant positive associations among AgNOR and Ki-67 scores with histologic grade and mitotic score were detected. Fifty-four dogs had adequate follow-up examinations and were included in survival analysis and evaluation of prognostic factors. Overall median survival time was > 1,306 days. Twelve of 54 (22%) dogs died of tumor-related causes. Metastatic disease developed in 8 of 54 (15%) dogs. Results of univariate analysis indicated that increased mitotic score, increased AgNOR score, increased Ki-67 score, incomplete surgical margins, noncurative intent surgery, Ki-67 score greater than the median Ki-67 score, and AgNOR score greater than the median AgNOR score were prognostic factors for decreased survival time. Results of multivariate analysis indicated that increased AgNOR score was the only prognostic factor for decreased survival time.
Conclusions and Clinical Relevance—Results suggested that AgNORs and possibly Ki-67 should be routinely evaluated with histologic grading for STSs in dogs.
Objective—To compare the Kiupel (2 categories) and Patnaik (3 categories) histologic grading systems for predicting the presence of metastasis at the time of initial examination in dogs with cutaneous mast cell tumors (MCTs).
Design—Retrospective case series.
Animals—386 client-owned dogs with cutaneous MCTs.
Procedures—Medical records of dogs with newly diagnosed, histologically confirmed cutaneous MCTs that had undergone complete clinical staging were reviewed for clinical and histopathologic data.
Results—All Patnaik grade 1 MCTs (n = 52) were classified as Kiupel low-grade MCTs, and all Patnaik grade 3 MCTs (43) were classified as Kiupel high-grade MCTs. Of the 291 Patnaik grade 2 MCTs, 243 (83.5%) were classified as Kiupel low-grade tumors, and 48 (16.5%) were classified as Kiupel high-grade MCTs. Dogs with Patnaik grade 3 MCTs were significantly more likely to have metastases at the time of initial examination than were dogs with grade 1 or 2 MCTs (OR, 5.46), and dogs with Kiupel high-grade MCTs were significantly more likely to have metastases than were dogs with Kiupel low-grade MCTs (OR, 2.54). However, 3 of 52 (5.8%) dogs with Patnaik grade 1 tumors, 48 of 291 (16.5%) dogs with Patnaik grade 2 tumors, and 44 of 295 (14.9%) dogs with Kiupel low-grade tumors had metastatic disease.
Conclusions and Clinical Relevance—Findings indicated that in dogs with cutaneous MCTs, prognostication should not rely on histologic grade alone, regardless of grading system used, but should take into account results of clinical staging.