Primary skeletal muscle anaplastic large cell lymphoma mimicking dermohypodermatitis

Anaplastic large cell lymphoma (ALCL) is a non-Hodgkin’s lymphoma (NHL) characterized by a strong expression of CD30. ALK-ALCL is a rare subtype that typically affects older adults and has a poor prognosis. It rarely arises in the skeletal muscle, particularly with primary involvement. Herein, we report the case of ALK-ALCL with primary involvement of the muscle. A 69-year-old male patient presented with fever, an erysipeloid placard in the axillary cavity, and the lateral and anterior chest wall initially treated with antibiotic therapy without improvement. A CT scan revealed a tumor proliferation in the pectoralis minor muscle, whose anatomopathological and immunohistochemical studies were in favor of ALCL. ALCL may mimic common dermatological conditions, including dermohypodermatitis. Therefore, in cases where symptoms do not resolve after conventional treatment, radiological examinations or even a biopsy should be considered to determine the cause of the symptoms and to initiate an appropriate treatment strategy.