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Today's VeTerinary PracTice | January/February 2016 | tvpjournal.com common neoPlasTic skin lesions in dogs & caTs Peer reviewed 34 Management. Most tumors diagnosed as basal cell tumors via cytology are easily cured with narrow surgical excision. If histopathology reveals a basal cell carcinoma, complete staging, including locoregional lymph node aspiration, chest radiography, and abdominal ultrasonography, is recommended. The malignant variant of this disease is rare enough that studies evaluating chemotherapy are not available. If histology confrms a mass as malignant, chemotherapy may be of beneft. Histiocytoma Description. Histiocytomas affect primarily young dogs, but they may arise at any age. These tumors have not been identifed in cats. Diagnosis. Grossly, histiocytomas have a distinctive appearance: they are raised, rounded, and alopecic and have small indentations all over ("pock marked"), which create an appearance similar to the surface of a strawberry. The tumors are also described as "button-like" because of their shape (Figure 13). These benign tumors will regress on their own, often over several months' time. As they do so, the surface may become ulcerated and intermittently bleed. Experienced practitioners may diagnose these tumors on the basis of gross appearance alone, although cytologic confrmation is suggested. On cytology, histiocytomas are in the round cell tumor category. They may be confused with other round cell tumors, such as plasma cell tumors or poorly granulated MCTs. Despite their benign behavior, histiocytomas often exhibit cytologic features of malignancy, such as numerous mitotic fgures and marked anisocytosis (Figure 14 ). Caution needs to be used in interpreting these features, and FIGURE 12. Cytology of a trichoblastoma; note the cluster of small round to cuboidal cells with small amounts of cytoplasm and relatively uniform nuclei (Diff Quik stain; magnifcation, 50×). FIGURE 13. A 2-cm diameter, round, raised, mostly hairless lesion on the antebrachium of a 7-month-old castrated male cocker spaniel, consistent with the classic clinical appearance of a histiocytoma. FIGURE 14. Cytology of the histiocytoma in Figure 13; note the population of round cells with moderate to large amounts of cytoplasm and distinct cytoplasmic margins (the cells look "outlined" due to clearing of the cytoplasm at the periphery). Prominent anisocytosis can be seen, as well as one mitotic fgure (Diff Quik stain; magnifcation, 50×). Laura D. Garrett Laura D. Garrett, DVM, Diplomate ACVIM (Oncology), is a clinical associate professor in oncology and Chief of Staff of the Veterinary Teaching Hospital at University of Illinois College of Veterinary Medicine. Dr. Garrett received her DVM from University of Illinois, completed an internship at University of Minnesota, and completed an oncology residency at University of Wisconsin–Madison. She is a noted national and international speaker and has published on the topics of canine lymphoma, feline hematology, clinical trials, and communication. After working in a New Zealand specialty clinic, Dr. Garret was on faculty at Kansas State University.