Benign rheumatoid nodule in the soleus muscle. Case report

Abstract Benign rheumatoid nodules are subcutaneous nodules, identical in morphology and histology to the nodules that develop over the course of rheumatoid arthritis (RA); they present in individuals with no symptoms of arthritis and with negative rheumatoid factor (RF). This article introduces the case of a 46-year-old caucasian male who consulted for a tumour in his right leg. He tested negative for rheumatoid factor, anti-citrullinated protein antibodies, antinuclear antibodies, and antineutrophil cytoplasmic antibodies, as well as for acute phase reactants. A musculoskeletal ultrasound showed a solid tumour of 3.5 × 1.5 cm with well-defined margins in the soleus muscle, and with a heterogeneous hypoechoic structure with intra- and peri-lesional vascularisation. The MRI showed a fibrous tumour with no signs suggestive of aggressive growth. An ultrasound-guided biopsy showed the characteristic histology of a rheumatoid nodule. The clinical presentation, diagnosis, differential diagnosis, and treatment of benign rheumatoid nodules are discussed.