Expression of epithelial and neuroendocrine markers within canine apocrine gland anal sac adenocarcinoma (AGASACA) and the relationship to peripheral hypercalcemia and parathyroid hormone-related protein (PTHrP) expression
Apocrine gland anal sac adenocarcinoma (AGASACA) of the dog is a frequently invasive and metastatic tumor and is commonly associated with peripheral hypercalcemia due to circulating elevated parathyroid hormone-related protein (PTHrP). As the tumor name implies, this neoplasm is attributed to apocrine gland origin, and special staining is not typically performed for additional investigation. Few studies have pursued additional characterization of these masses and identified evidence of neuroendocrine differentiation within some canine anal gland tumors. At this time, however, the significance of this finding is unknown, though additional examination may reveal relationships between neuroendocrine differentiation and the occurrence of peripheral hypercalcemia, PTHrP expression (a frequent underlying cause of peripheral hypercalcemia), metastasis at the time of diagnosis, and/or patient survival time. The first objective of this study was to validate a PTHrP antibody for use in canine histology sections of AGASACA tumors. Secondly, we set out to determine if tumors that display neuroendocrine differentiation more commonly express PTHrP (a frequent underlying cause of peripheral hypercalcemia). A subset of canine anal sac apocrine gland tumors was retroactively evaluated via immunohistochemistry to determine tissue differentiation, histologic tumor pattern, and PTHrP expression. The third objective was to determine if a correlation between tumor PTHrP expression and peripheral hypercalcemia existed. The presence or absence of peripheral hypercalcemia was recorded by retrospective review of medical records for all patients within the study. Lastly, the relationships between histologic pattern and neuroendocrine differentiation, PTHrP expression, and peripheral hypercalcemia were evaluated. Tumor patterns were recorded during microscopic evaluation and the tumors were separated into one of seven groups based on their specific pattern. There was no significant relationship between hypercalcemia and histologic tumor pattern. Results did show a significant correlation between hypercalcemia and positive PTHrP expression compared to the absence of PTHrP expression. No statistical analysis was performed regarding neuroendocrine differentiation as no tumors showed positive reactivity.
AGASACA, apocrine gland anal sac adenocarcinoma, PTHrP, parathyroid hormone-related protein, hypercalcemia, neuroendocrine
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign