Diffuse large B-cell lymphoma presenting as sternal mass in a patient with ankylosing spondylitis: a case report study

Primary bone lymphoma is a rare entity that constitutes less than 1% of all non-Hodgkin lymphomas and 3–5% of malignant bone tumors. Chronic immune and inflammatory diseases carry a level of risk for the development of malignancies that is correlated with the disease severity. There is conflicting evidence regarding the risk of lymphoma in spondyloarthritis. CASE PRESENTATION: The authors present a rare case of primary diffuse large B-cell lymphoma of the sternum in a 41-year-old Iranian woman with ankylosing spondylitis (AS). Physical examination revealed a 7×7.5 cm firm swelling of the anterior midline chest wall above the breasts, and MRI showed a lesion within the sternal marrow with an associated soft-tissue mass in the anterior aspect of the sternum. Following core-needle biopsy under ultrasound guidance, a histopathological study demonstrated diffuse sheets of large noncleaved atypical cells with large multilobated prominent nuclei and fine chromatin compatible with diffuse large B-cell lymphoma. CLINICAL DISCUSSION: Primary and exclusive involvement of the sternum is an uncommon presentation of lymphoma. Radiological, histological, and clinical characteristics of primary bone lymphoma can resemble those of other medical disorders. Although infrequent, existing evidence shows that AS seems to be associated with a small but significant risk for malignancy. CONCLUSION: Even though inflammatory involvement of the anterior chest wall could be a common clinical finding in patients with AS, it is recommended that anterior chest wall pain or any mass almost always needs comprehensive assessment and imaging evaluation in such patients to avoid any delayed diagnosis, misdiagnosis, and ensuing morbidity or mortality.