Mast cell
tumor (MCT) is a frequent cutaneous
tumor in dogs, with a variable biological behavior. Studies correlate cytologic and histopathologic features of MCTs with their biological behavior, prognosis, and response to treatment. The use of preoperative
opioids is common in canine patients undergoing surgical removal of these
tumors. Certain
opioids can induce or downregulate mast cell degranulation and influence
cancer progression. The aim of the present study was to investigate whether the administration of
morphine or
butorphanol during surgical excision of canine cutaneous MCTs affects their cytologic and histopathologic appearance, thus influencing cytologic and histopathologic grading. This was a prospective, blinded, randomized, cohort clinical study. Forty-five dogs with cutaneous MCTs were randomly allocated into three groups according to preanaesthetic medication:
dexmedetomidine combined with
morphine (group M) or
butorphanol (group B) or
normal saline (group C). Cytologic specimens and histopathologic samples were obtained both prior to and after surgery. Samples were graded according to Kiupel's and Patnaik's systems, examined immunohistochemically for Ki-67
protein (Ki-67) and c-kit proto-oncogene product (KIT) expression, and histochemically for argyrophilic nucleolar organizing regions (
AgNORs). Based on both Kiupel's and Patnaik's systems, no statistically significant differences were noted concerning the number of cases with grading discrepancies in grades allocated prior to versus after surgery among the groups. The same applied for cytological grading and immunohistochemical and histochemical evaluation. It seems that administration of
morphine or
butorphanol as part of the
preanesthetic medication for surgical removal of canine cutaneous mast cell
tumors does not influence histopathologic and cytologic grading of MCTs.