49 Histiocytoma


The history (age, breed and duration of onset) and clinical examination were suggestive of a cutaneous histiocytoma; however, the other differentials could not be ruled out on clinical examination alone. Boxers in particular are predisposed to mast cell tumour, so confirmation of the diagnosis of histiocytoma was essential, before deciding on the best course of treatment.

A fine-needle aspirate sample was obtained aseptically with a 23-gauge needle. The author’s technique is to insert the needle into the lump and redirect it in and out in several directions and then remove it. A 10-ml syringe containing air is attached to the needle and the contents expressed onto a clean microscope slide by pushing in the plunger. Usually, this method produces a good harvest of cells. The slide is stained with modified Wright’s stain or sent to a cytopathologist. A correct interpretation of the sample is essential to avoid a misdiagnosis, which could lead to major surgery or to other life-threatening treatments.

In this case, the fine-needle aspirate revealed a population of mononuclear cells with oval to round nuclei (some with indented nuclear membranes) and pale blue cytoplasm (Fig. 49.2). The cells lacked the granules that one would expect to see with mast cells, thus ruling out a mast cell tumour. Plasmacytomas have a smooth surface that is rarely ulcerated. Cells from a plasmacytoma generally have a more basophilic staining cytoplasm, and the cells show increased anisocytosis (variation in cell size) and anisokaryosis (variation in the size of the nucleus). Sebaceous gland adenomas and hyperplasia yield epithelial cells containing lipid vacuoles, which were not seen in this case, and infectious granulomas would yield large numbers of inflammatory cells such as neutrophils and macrophages that also were not present in this case.

Sep 3, 2016 | Posted by in SMALL ANIMAL | Comments Off on Histiocytoma

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