THE CASE:
A 59-year-old man, heavy smoker, with no medical history, who consulted for a sternal swelling starting from July 2019. The patient firstly consulted in November 2019.Systemic symptoms as fever, night sweating or weight loss were absent. The clinical examination revealed a firm painful mass of the manubrium. There were no inflammatory signs of the skin. A first chest computed tomography (CT) revealed a poorly limited osteolytic lesion of the manubrium measuring 20 x 13 x 40 mm with multifocal interruption of the anterior and posterior bony cortex. There was a deep extension to the mediastinal tissue as well as to superficial layers (figure 1). This scannographic aspect was very evocative of a chondrosarcoma. Computed tomographic scans of the head, abdomen, and pelvis did not reveal any suspicious lesion. There was no biological inflammatory syndrome and LDH rate was normal. Tuberculosis tests were negative, excluding a tuberculosis destruction of the sternum. A needle biopsy was realized and concluded to a non-specific inflammatory remodeling of striated muscle tissue. Unfortunately, it was not possible to continue the follow up because of COVID-19 epidemic, and the patient was lost of sight for 3 months. Meanwhile, the sternal mass increased in size and become more painful. A second CT scan showed a progression of the tumor (48 x 40 x 58mm) with a near contact with the brachiocephalic vein truncus (figure 2). After multi-disciplinary team discussion, and taking into consideration the high suspicion of a progressing sarcoma, it was decided to perform a surgical resection of the mass. Via a median skin incision facing the sternum, resection considered the whole manubrium with an extension to the upper part of the body of the sternum, the interior part of the clavicles and the anterior arch of the two first ribs from both sides. In the anterior mediastinum, there was a tight adhesion to the thymus and so resection was enlarged to this later. Reconstruction was performed with a polytetrafluoroethylene (PTFE) mesh and covered by the two pectoralis major (figure 3).
Postoperative course was uneventful. On macroscopy, manubrium was enlarged and the cut surface was white, homogeneous. The cortical bone was deformed with focal rupture. The posterior tissue contained lymph nodes measuring 5 mm to 3cm. Histological examination revealed sternal and lymph nodes infiltration by sheets of large round cells with scanty cytoplasm and round nuclei containing 2 or 3 nucleoli; mitoses were numerous. There was no chondroid differenciation. Immuno-histochemical staining showed high and diffuse positivity for CD20 and CD79a (Figure 4). Margins were negative. Prospectively, no secondary location is found and sternal location is the unique site. Level of LDH was normal. Based on morphologic finding and clinical findings (a single skeletal site with regional lymph node involvement), a primary B large cell lymphoma of sternum was posed. This tumor was staged IIE, and the patient received 6 cycles of R-CHOP protocol.