LAUSR

747 Antinuclear antibodies and autoantibodies to extractable nuclear antigens (including anti-Jo-1, anti-Mi-2 and antiTIF1-gamma) were negative. A CT scan of the chest and abdomen showed several enlarged lymph nodes in the right jugular area and a tumour in the left upper lobe. One lymph node was excised for histological examination. It revealed metastatic spread of a poorly-differentiated squamous cell carcinoma of the lung. After treatment with intravenous immunoglobulins and steroids, regression of myositis and the cutaneous lesions was achieved. The inoperable lung cancer was treated with pembrolizumab, paclitaxel, and cisplatin. The patient died two months later of pneumonia. We report a patient with squamous cell lung cancer, necrobiotic xanthogranuloma, and polymyositis. In approximately 80% of cases, necrobiotic xanthogranuloma is accompanied by monoclonal gammopathy [1]. Necrobiotic xanthogranuloma may also be associated with blood cancers or lymphoproliferative disorders [2, 3]. No cases associated with lung cancer as in our patient or other solid tumours have been reported so far. In our patient, monoclonal gammopathy and leukaemia were ruled out based on immuno-electrophoresis and flow cytometric analysis. Polymyositis is one of many inflammatory myopathies and is accompanied by symmetrical proximal muscle weakness. About 30% of elderly patients with dermatomyositis/polymyositis have an underlying malignancy. Cancer is less frequent in the presence of polymyositis than dermatomyositis [4, 5]. Associated cancers include those of the ovary, lung, breast, gastrointestinal tract, pancreas, nasopharynx, testicles, and non-Hodgkin’s lymphoma. An association between polymyositis and lung cancer has been rarely reported [6]. The pathophysiology of polymyositis and malignancy is not well understood. Some patients with paraneoplastic polymyositis develop autoantigens common to cancer and muscle tissue, resulting in muscle damage [7]. Paraneoplastic polymyositis is frequently resistant to treatment because of the underlying malignancy. On the other hand, the treatment of cancer may lead to the regression of myositis. To the best of our knowledge, this is the first reported case of necrobiotic xanthogranuloma and polymyositis in a patient with lung cancer. The simultaneous occurrence of these two potentially paraneoplastic diseases in the same patient may constitute a new clinical entity.