A previously undescribed cutaneous paraneoplastic syndrome in a cat with thymoma.

ABSTRACT

BACKGROUND: Exfoliative dermatitis is a well-recognized cutaneous paraneoplastic syndrome (PNS) associated with thymoma in cats, of which the clinical and histopathological presentation has been well-characterized. OBJECTIVES: To describe a novel clinical skin manifestation associated with thymoma in a cat. ANIMAL A 14-year-old neutered female domestic short hair cat. METHODS AND MATERIALS Physical, abdominal ultrasonographic, thoracic radiographic, ultrasonographic and computed tomographic examinations, histopathological assessment of the skin and mediastinal mass. RESULTS: The cat was presented with noninflammatory alopecia, with a dorsal multifocal distribution. Examination of the alopecic areas using a dermascope indicated an apparent lack of follicular ostia. Histopathological assessment of alopecic areas confirmed follicular and epidermal atrophy, trichilemmal keratinization and mild orthokeratotic hyperkeratosis. Diagnostic imaging revealed a mediastinal mass, which was surgically removed. Histopathological and immunohistopathological examination of the mass was consistent with a thymoma, associated with multiloculated cyst formation and multifocal cholesterol granulomas. Following surgery, hair re-growth was noted in the previously alopecic areas. The cat was euthanized 3.5 months later because of recurrent chylothorax suspected to be a postoperative complication. The alopecic lesions had improved markedly. CONCLUSIONS AND CLINICAL IMPORTANCE Thymoma-associated PNS might not always manifest as an exfoliative dermatitis and should be considered in the differential diagnosis of multifocal noninflammatory alopecia.