Histologic evaluation of parovarian nodules in the cat

A notable, although relatively uncommon, finding during feline ovariohysterectomy is the presence of parovarian nodules, located proximal to the ovary, near or within the ovarian vascular bundle. They are usually 2-3 mm in diameter, white-to-tan in color and glandular in appearance. The objective of this study was to either decisively reinforce the existing findings reported in the literature, which suggest that these parovarian nodules are incidental adrenocortical nodules that are clinically and surgically insignificant, or capture any samples that were not ectopic adrenal tissue in order to characterize them histologically.

Ninety-one formalin-preserved tissue sections containing parovarian nodules were collected during routine feline elective ovariohysterectomy and evaluated histologically.

Definitive histologic information was obtained from 73/91 (80.2%) submitted samples. Fifty-two of 73 (71.2%) samples were determined to contain accessory adrenal gland cortex. Twenty of 73 (27.4%) samples were determined to contain residual mesonephric structures. While accessory adrenocortical nodules were found bilaterally in cats of all ages, mesonephric structures were predominantly right-sided, and only found in one cat over the age of 1 year. Ectopic or accessory ovarian tissue was not found in any of the samples.

This study adds to the existing body of data which suggest these nodules are incidental structures that do not need to be removed during surgical sterilization. However, further in vivo studies with larger sample sizes and years of follow-up would be required to more definitively prove this theory.