Unusual involvement of scalp and bilateral kidneys in an aggressive mediastinal diffuse large B cell lymphoma: documentation by FDG-PET imaging.

In the present communication, an unusual combination of scalp soft tissue and underlying brain involvement with intact skull bone coupled with bilateral renal involvement from a mediastinal diffuse large B cell lymphoma (DLBL) is presented. A 45-year-old man, a diagnosed case of mediastinal DLBL with bilateral lung involvement, was treated with conventional 6 cycles of chemotherapy and local external radiotherapy with initial good treatment response evidenced by considerable regression in mass size and regression in pulmonary lesions. Three months later, he returned with complaints of soft tissue swelling over the scalp; one of them in the high parietal bone and the other over the occipital region. A whole body FDG-PET at this time showed 2 moderate-sized foci in the scalp (with preservation of both tables of skull bone) and corresponding large foci in the brain parenchyma beneath, a superior mediastinal focus, a few foci in the apical and lower zone of left lung, extensive irregular uptake in the right pleura and the right lung parenchyma coupled with a loculated effusion in its lower zone and studded foci of hypermetabolism throughout the bilaterally enlarged kidneys. CT of the head confirmed the FDG-PET findings and histopathology of the biopsy from the scalp swelling was suggestive of DLBL. Ultrasound imaging of the abdomen showed lobulated bilaterally enlarged kidneys with multiple hypoechoic areas within them. The patient underwent palliative local external radiotherapy to the brain and systemic chemotherapy with poor clinical results with raised serum beta-2 microglobulin and serum LDH levels and deranged renal function. The patient died within a month after the FDG-PET study. The event of scalp and bilateral renal involvement from DLBL is rare in lymphoma literature and this report highlights that such unusual events can occur as part of widespread dissemination and underscores the importance of whole-body imaging with FDG-PET.