O07 - Alkaline Phosphatase Cytochemistry in the Diagnosis of Canine and Feline Primary Pulmonary Neoplasia

Abstract: Background: Distinguishing primary and secondary pulmonary neoplasia can be challenging via cytology. No rapid, inexpensive diagnostic tool to aid in this distinction is currently available. Alkaline phosphatase cytochemistry (ALP-CC) has been used in people to identify primary pulmonary carcinomas. We hypothesized this approach could be applied to canine and feline lung aspirates.

Objectives: The primary objectives of this study were to evaluate the utility of ALP-CC in aiding in the diagnosis of primary pulmonary epithelial neoplasia in dogs. Secondary objectives including reporting ALP staining characteristics of canine mesothelium and feline pulmonary lesions.

Animals: Hospital population and archived samples.

Methods: A retrospective case search was conducted to identify canine and feline cases with contemporaneous cytology and histopathology reports. Neoplastic and non-neoplastic etiologies were included. Slides were prospectively stained for ALP activity. Sensitivity and specificity were calculated using the histopathologic diagnosis as the gold standard. Mesothelial cells from cavitary lavage were previously collected as part of a different study and ALP activity was evaluated.

Results: Fifty canine cases and six feline cases met inclusion criteria. Ninety percent of canine primary pulmonary epithelial neoplasms were ALP-positive. The sensitivity and specificity for assignment of pulmonary epithelial origin among all samples and among all neoplastic lung lesions were 90% and 80%, and 90% and 78% respectively. Canine mesothelial cells did not display ALP positivity. Feline pulmonary carcinomas displayed ALP positivity.

Conclusions: ALP-CC has good sensitivity and specificity for aiding in the diagnosis of canine primary pulmonary epithelial neoplasia, and mesothelial cells do not display ALP-positivity.