Cytologic Evaluation as a Diagnostic Tool to Differentiate Adrenocortical Tumors and Pheochromocytomas

Abstract

Background: The utility of cytologic evaluation to distinguish adrenocortical tumors and pheochromocytomas in dogs has not been thoroughly investigated, partly because of the perceived risks of the procedure.

Objectives: Report test characteristics of fine needle aspiration (FNA) and cytologic evaluation for differentiation of adrenocortical tumors and pheochromocytomas in dogs. Complications associated with FNA also were recorded.

Animals: Thirty-eight dogs with 40 adrenal tumors that had FNA and cytologic evaluation performed before adrenalectomy were included in the study from three institutions. Tumors included 17 pheochromocytomas, 21 adrenocortical tumors, 1 concurrent adrenocortical adenoma and pheochromocytoma, and 1 malignant neoplasm.

Results: Of the 40 FNA cytologic aspirations performed, 35 (87.5%) had a predominant cell type identified and therefore were considered of diagnostic quality. Of these, 30 (85.7%) correlated with the final histopathological diagnosis. When all samples were included, FNA and cytologic evaluation had a sensitivity of 77.3%, specificity of 76.5%, positive predictive value of 81.0%, negative predictive value of 72.2%, and accuracy of 76.9% for identifying adrenocortical tumors. For pheochromocytomas, these values were 72.2%, 95.2%, 92.8%, 80.0%, and 84.5%, respectively. Six (15.9%) dogs had self-limiting complications associated with the FNA procedure.

Conclusion and clinical importance: Fine needle aspiration and cytologic evaluation of adrenal tumors has a low complication rate and can help differentiate adrenocortical tumors and pheochromocytomas. Thus, cytologic evaluation of adrenal tumors should be considered to help differentiate adrenal tumors and allow more individualized treatment of affected dogs.

Keywords: adenoma; adrenal; aspirate; carcinoma; cytology.

FIGURE 1

Cytology of canine adrenocortical adenoma. Fine needle aspirate of an adrenal mass was markedly cellular and contained numerous variably sized clusters of relatively uniform large oval to polygonal epithelial cells. The nuclear to cytoplasmic ratio was low. Cells exhibited mild to rarely moderate anisocytosis and anisokaryosis. The cells contained round nuclei with occasional one to two prominent nucleoli and finely to coarsely stippled chromatin. The cytoplasm is abundant and pale pink to amphophilic in color. Occasional cells contained numerous distinct small cytoplasmic vacuoles. (Wright‐Giemsa; 50× oil objective).

FIGURE 2

Cytology of canine pheochromocytoma. Fine needle aspirate of an adrenal mass was markedly cellular with numerous naked nuclei and rare to occasional intact cells consistent with endocrine/neuroendocrine origin. Cells were arranged individually and in small clusters. Intact cells displayed mild anisocytosis and anisokaryosis. The nuclear to cytoplasmic ratio was high. Cells were oval to polygonal with a small amount of medium blue cytoplasm that occasionally contained moderate numbers of fine pink granules. The nuclei were oval and centrally placed with coarsely stippled chromatin and inconspicuous nucleoli. (Wright‐Giemsa; 100× oil objective).