Objective—To reexamine (via immunohistochemical techniques) canine tissue samples that had been previously classified as gastrointestinal leiomyosarcomas (GILMSs), identify and differentiate gastrointestinal stromal tumors (GISTs) from GILMSs, and compare the biological behavior and clinical course of GISTs and GILMSs in dogs.
Design—Retrospective case series.
Procedures—Medical records of 42 dogs for which a histologic diagnosis of GILMS was confirmed were reviewed for signalment, clinical signs, physical examination findings, results of initial diagnostic tests, surgical findings, adjunctive treatment, location of the tumor, completeness of resection, and outcome after surgery. Archived tumor tissue specimens from each dog were restained via immunohistochemical techniques to differentiate tumor types. Long-term follow-up information was obtained from the medical record or through telephone interviews with owners and referring veterinarians.
Results—On the basis of immunohistochemical findings, 28 of 42 tumors were reclassified as GISTs and 4 were reclassified as undifferentiated sarcomas; 10 tumors were GILMSs. In dogs, GISTs developed more frequently in the cecum and large intestine and GILMSs developed more frequently in the stomach and small intestine. Median survival times for dogs with GISTs and GILMSs were 11.6 and 7.8 months, respectively; if only dogs surviving the perioperative period were considered, median survival times were 37.4 and 7.8 months, respectively. These differences, however, were not significant.
Conclusions and Clinical Relevance—In dogs, many previously diagnosed GILMSs should be reclassified as GISTs on the basis of results of immunohistochemical staining. The biological behavior of these tumors appears to be different.
Objective—To determine clinical activity and toxic effects of lomustine when used to treat cats with mast cell tumors (MCTs).
Design—Retrospective case series.
Animals—38 cats with measurable, histologically or cytologically confirmed MCTs treated with lomustine at a dosage ≥ 50 mg/m2.
Procedures—Medical records were reviewed to determine response to treatment and evidence of drug toxicoses. The Kaplan-Meier method was used to estimate remission duration.
Results—26 cats had cutaneous MCTs, 7 had MCTs of the mesenteric lymph nodes, 2 had gastrointestinal tract MCTs, 2 had hepatic MCTs, and 1 had MCTs involving multiple organs. Targeted lomustine dosage was 50 mg/m2 in 22 cats and 60 mg/m2 in 16 cats. Median administered dosage of lomustine was 56 mg/m2 (range, 48 to 65 mg/m2), and median number of doses administered was 2 (range, 1 to 12). Seven cats had a complete response and 12 had a partial response, for an overall response rate of 50%. Median response duration was 168 days (range, 25 to 727 days). The most common toxicoses were neutropenia and thrombocytopenia.
Conclusions and Clinical Relevance—Results suggested that lomustine had activity against MCTs in cats and was well tolerated. Further, findings suggested that treatment with lomustine should be considered for cats with MCTs for which local treatment is not an option.
Objective—To determine the biological behavior of
liposarcomas in dogs and identify clinical signs, the
effect of treatment on survival time, and potential
Animals—56 dogs with histologically confirmed liposarcoma.
Procedure—Information was obtained on signalment,
tumor size, location of the tumor, stage of disease,
remission duration, overall survival time, cause
of death, type of surgery (incisional biopsy, marginal
excision, or wide excision), and any additional treatments
Results—Surgery consisted of incisional biopsy in 6
dogs, marginal excision in 34, and wide excision in 16.
Twenty-five dogs had histologic evidence of tumor
cells at the surgical margins and 28 did not (status of
the margins was unknown in 3 dogs). Twelve of 43
dogs had local recurrence. Median survival time was
694 days, and the only factor significantly associated
with survival time was type of surgery performed.
Median survival times were 1,188, 649, and 183 days,
respectively, for dogs that underwent wide excision,
marginal excision, and incisional biopsy. Factors that
were not found to be significantly associated with
survival time included tumor size, status of the margins,
tumor location, and histologic subtype.
Conclusions and Clinical Relevance—Results suggest
that in dogs, liposarcomas are locally invasive
neoplasms that rarely metastasize and occur primarily
in appendicular or axial locations and that wide excision
is preferred to marginal excision when feasible.
(J Am Vet Med Assoc 2004;224:887–891)