Erythema Nodosum Revealing Metastatic Lung Cancer.

Erythema nodosum (EN) is an inflammatory condition of the subcutaneous fat and has been reported in patients with haematological malignancies (lymphomas) or solid tumours. Lung cancer is the most common cause of paraneoplastic syndrome. We report a case of EN occurring as a paraneoplastic disease. A 48-year-old Tunisian woman, a non-smoker with no relevant medical history, presented with painful, erythematous, firm nodules on her legs with ankle swelling. The patient did not report any other symptoms. There were no abnormalities on examination except for moderate fever. An extensive infectious and immunological investigation was negative. Antistreptolysin antibodies were undetectable. Chest radiography showed a focal opacity in the right lung and a CT scan revealed a mass in the lower right pulmonary lobe with hilar and mediastinal lymphadenopathies, a nodule in the right adrenal gland, condensation in the iliac bone and multiple bilateral nodular cerebral expansive processes. Bronchial biopsies revealed a primitive and moderately differentiated adenocarcinoma. No argument for tuberculosis or sarcoidosis was found. LEARNING POINTS: Erythema nodosum (EN) can be idiopathic.EN has rarely been associated with lung cancer and so the association may be coincidental in our patient.The lung cancer was easily identified by chest x-ray in this case and in cases described in the literature. © EFIM 2021.