Morphological study of apocrine gland tumors in domestic Richardson's ground squirrels (Urocitellus richardsonii)

The morphology of 58 apocrine tumors from 31 domestic Richardson's ground squirrels (Urocitellus richardsonii) was examined, comparing tumor subtypes with clinical information and histological findings. The squirrels included 23 males (74%) and 8 females (26%). Of the 58 tumors, 36 (62%) were located from the cervical skin to the dorsal skin, 17 (29%) were from the perioral region to the cheek, and the location was unrecorded for the remaining 5 squirrels (9%). Histologically, 49 tumors (84%) were apocrine adenocarcinomas, 6 were apocrine adenomas (10%), and 3 were apocrine cysts (5%). The 49 apocrine adenocarcinomas were subclassified as 16 (33%) cystic papillary type, 16 (33%) tubulopapillary type, 12 (24%) solid type, and 5 (10%) micropapillary invasive type. Fisher's exact test revealed correlations between tumor subtypes and tumor diameters, nuclear atypia, tumor margins, vascular invasion, and periodic acid-Schiff (PAS) positivity. This study showed a predominance of apocrine adenocarcinomas with various histological subtypes. In addition, subclassification of these tumors was useful for predicting the biological behavior of apocrine gland tumors in Richardson's ground squirrels.

Automated summary

This study examined the morphology of 58 apocrine tumors in 31 domestic Richardson's ground squirrels and compared tumor subtypes with clinical information and histological findings. The majority of the tumors were apocrine adenocarcinomas, with the cystic papillary and micropapillary invasive types being the most common. There were correlations between tumor subtypes and tumor diameter, nuclear atypia, tumor margins, vascular invasion, and PAS positivity.