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Gross and microscopic pathological findings in a sebaceous gland carcinoma of the perineum and vulva in a Friesian cow

SEBACEOUS gland lesions that have been previously described include sebaceous hyperplasia, sebaceous adenoma, sebaceous epithelioma and sebaceous gland carcinoma, which is rare (Yager and Scott 1993). Sebaceous gland tumours are common epithelial skin tumours in dogs, but are rare in other domestic animal species (Pulley and Stannard 1990,Yager and Scott 1993). Rostami and others (1994) found no sebaceous gland tumours in a comprehensive 10-year study of domestic species. Although malignant sebaceous gland tumours have been observed to occur in the eyelids of dogs and cats (Pulley and Stannard 1990), reports of the condition are scarce. This short communication describes, to the authors’ knowledge for the first time, a sebaceous gland carcinoma affecting the perineum and vulva of a Friesian cow in Tanzania. A five-year-old Friesian cow was admitted to the university veterinary clinic for management of an ulcerated nodular growth on the perineum. The history indicated that the lesion had started as an elevated, button-like ulcer on the lower part of the perineum. Clinical and surgical intervention had not arrested the development of the lesion; instead, it had continued to expand rapidly, developing into an abnormal mass of tissue. Immediately after detection, the lesion was treated as an infected wound, with local dressing and systemic antibiotics. Each time it was cleaned for dressing, the wound bled. Three weeks after it had first been noticed, the lesion had grown into a large, fungating (a nodular ‘fungus’ or ‘cauliflower’-shaped proliferating growth, with a crater-like, ulcerating and necrotising wound) mass of tissue, extending to cover the whole perineum and both labia of the vulva. Histopathological studies on biopsy samples of the lesion suggested that it had features of a squamous cell carcinoma. Given this diagnosis and the associated poor prognosis, the cow was euthanased with an intravenous overdose of sodium pentobarbitone. Tissue samples of the lesion and local lymph nodes were taken and fixed in 10 per cent neutral buffered formalin for histopathological investigation. Grossly, the tumour presented as a cauliflower-like inflorescence of a nodular mass of tissue, fungating and locally invading the tissues of the perineum and both labia of the vulva. The left side of the vulva was worse affected than the right (Fig 1). The surface of the tumour was nodular and ulcerated. It appeared to have involved the perineum and vulva, and the infundibulum of the vagina showed evidence of neoplastic invasion. No metastases were detected in the regional lymph nodes. Histopathologically, the lesion presented compact masses of irregularly shaped epithelial cells, closely packed in poorly circumscribed, sheet-like extensions infiltrating haphazardly into the dermis (Fig 2). The constituent cells had faint outlines; their nuclei varied in size and shape but most were round or ovoid (Fig 2). Mitotic figures were frequent, and occasional populations of cells exhibited subtle differentiation into early features characteristic of sebaceous gland cells. These populations were composed of a mixture of immature, hyperchromatic, undifferentiated cells, tall columnar cells reminiscent of undifferentiated basal cells, mostly at the periphery of the cell masses, and cells bearing subtle evidence of minute fatty vacuolations and differentiation towards characteristic sebaceous gland cells (Fig 2). In addition, there were many foci of differentiation into squamous epithelium and concentric keratinisation, most of them located more or less at the centre of the epithelial cell masses. The bizarre gross appearance of the tumour, its rapid growth into a fungating mass of tissue, the ulceration, illdefined borders, frequent mitotic figures, and the invasive growth of the tumour into the deeper dermis and subcuta-