Feline bowenoid in situ carcinoma

Feline Bowenoid in situ carcinoma (BISC) is a rare variant of feline squamous cell carcinoma that presents as multiple discrete plaques of epidermal hyperplasia and dysplasia. For a long time it was assumed that feline papilloma virus might play a role in this disease. Now it has been proven by using consensus primers – and even more the virus isolated is closely related to human papillomvirus[1].

The condition is seen primarily in cats over 10 years of age[2]. Quite a number of cases have been described in FIV-positive cats[3]. The distribution of lesions is multicentric but involves mainly the face, shoulders and limbs. Clinically, it is characterized by non-pruritic papules, nodules, and hyperkeratotic and hyperpigmented plaques which can become ulcerated. In some cases, Demodex spp mites can be seen in the hair follicles within lesions.

Histologically, BISC lesions are characterized by irregular epidermal hyperplasia with broad rete ridges and full-thickness epidermal dysplasia. Hair follicle infundibula and isthmi may be involved in the hyperplastic process[4].

Their development is associated with the presence of a papilloma virus. The term in situ refers to a malignant proliferation of epidermal and follicular outer sheath cells that are not invasive into the underlying dermis. Unfortunately, lesions may progress over time into an invasive carcinoma. Metastasis is extremely uncommon. These lesions usually develop in systemically ill or immunosuppressed cats and are believed to be virally induced.

Various therapeutic options have been proposed but it seems that synthetic retinoids, notably acitretin, given orally at a dosage of 1 mg/kg BID until remission of lesions and then on alternate days, gives variable results depending on FIV retroviral status. This treatment requires regular monitoring: Schirmer tear testing every 2 months and measurement of serum cholesterol, triglyceride and hepatic enzymes.

Table 1. – Distinguishing SCC from BISC[5]

Feature BISC SCC
Hair color Nonwhite White
Lesion number Multiple Unique or bilateral
Localization Other locations Nose, ear tips, eyelids, lips
Form More or les circular Irregular
Erythema Moderate Marked
Surface Hyperkeratotic Crusty



  1. ↑ Guaguere, E & Prelaud, P (2000) A practical guide to feline dermatology. Merial, France
  2. ↑ Guaguere, E et al (1999) Vet Dermatol 10:61-67
  3. ↑ Miller, WH Affolter, VA & Scott, DW (1992) Vet Dermatol 3:177-182
  4. ↑ Baer KE, Helton K Baer KE, Helton K (1993) Multicentric squamous cell carcinoma in situ resembling Bowen’s disease in cats. Vet Pathol 30:535–543
  5. ↑ Adapted from Favrot, C. et al (2010) Clinical, Histologic, and Immunohistochemical Analyses of Feline Squamous Cell Carcinoma In Situ. Vet Pathol 46(1):25-33

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