Veterinary Medicine - February 2009 - (Page 75) 1A. Cytologic examination of a fine-needle aspirate of an anal sac adenocarcinoma reveals clustering of the cuboidal cells and indistinct cellular borders. Anal sac adenocarcinoma cells typically lack overt criteria of malignancy (Wright’s-Giemsa; 50x). (Photo courtesy of Joyce Knoll, VMD, PhD, DACVP.) 1B. Histologic section of adenocarcinoma of the apocrine gland of the anal sac. The lumen of the anal sac is in the center (black arrow), immediately surrounded by lymphocytic inflammation and clusters of normal apocrine glands (thin white arrow). Normal architecture to the left and far right is effaced by the lobulated adenocarcinoma (thick white arrow) (hematoxylin-eosin; 20x). (Photo courtesy of John H. Keating, DVM, DACVP.) in 40% to 72% of cases at presentation.3-8 This metastasis to the iliac lymph nodes can occur early in the course of disease while the anal sac tumor is still quite small.8 Lateral abdominal radiographic ndings can suggest a soft tissue opacity in the sublumbar region, causing ventral deviation of the colon. Abdominal ultrasonography has higher sensitivity than does radiography in detecting iliac lymphadenopathy and can better characterize the number and size of lymph nodes and evaluate the remainder of the abdomen for evidence of distant metastatic disease (Figure 2).1 Pulmonary metastatic disease occurs less commonly and can be identi ed as a nodular or diffuse pattern on thoracic radiographs.1 Other uncommon sites of metastasis include the spleen, liver, and lumbar spine.4 The information gathered during staging will help guide treatment and formulate a prognosis. 2. The ultrasonographic appearance of iliac lymphadenopathy due to metastatic anal sac adenocarcinoma in a dog. cellular borders are seen (Figure 1A). Despite this tumor’s aggressive biologic behavior, the cytologic appearance of the cells can be benign, with few criteria of malignancy apparent. Suppurative in ammation or necrosis identi ed in cytologic specimens can be misleading since tumors can be secondarily infected. In such cases, obtain a biopsy after appropriate antibiotic therapy.1 Biopsy may also be needed to distinguish between epithelial tumors involving the circumanal glands and apocrine glands of the anal sacs (Figure 1B). However, a lesion at the site of an anal sac often increases clinical suspicion of the tumor type. Staging tests include abdominal ultrasonographic and three-view thoracic radiographic examinations. Evidence of local spread to the iliac lymph nodes is common, occurring TREATMENT Because anal sac adenocarcinoma has a high rate of local metastasis and a locally invasive nature, a multimodal approach to treatment is typically recommended. The bene t of surgery and radiation has been shown in retrospective studies, while the role of chemotherapy is less clearly de ned. Medical management of hypercalcemia The clinical signi cance of hypercalcemia related to anal sac adenocarcinoma is not well-characterized. In most cases, this paraneoplastic syndrome resolves once the tumor is surgically removed.3 However, long-term complications of persistent hypercalcemia in dogs with unresectable disease are not well-established, and, in our experience, these dogs have not developed evidence of renal compromise. Nevertheless, judicious monitoring of blood urea nitrogen and creatinine VETERINARY MEDICINE February 2009 75
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