BackgroundRenal medullary carcinoma is one of the rarest malignancies arising from the kidney. Despite various aggressive therapeutic regimens, mortality remains significantly high (95%) with a median overall survival of 5 months. Furthermore, the scarcity of this malignancy renders randomized clinical trials impossible. We examined the expression of programmed death ligand 1 (PD-L1) in two new renal medullary carcinoma cases, investigated their responses to the PD-L1 inhibitor nivolumab and explored the predictive role of the rate of PD-L1 expression in such response.Case presentationTwo African-American patients (male and female) with sickle cell trait who presented to our center with hematuria and flank pain were diagnosed with metastatic renal medullary carcinoma. PD-L1 was expressed at rate of 25% and 60% in patient 1 and 2 respectively. Following nephrectomy, they were started on nivolumab. Patient 1 initially responded to the treatment with regression of metastatic lesions. However, following this early response, patient 1 who has been receiving nivolumab for more than 15 months, was noted to have a disease progression. Patient 2 had disease progression after 3 months of nivolumab therapy.ConclusionsAlthough PD-L1 is expressed in these patients with renal medullary carcinoma, response to nivolumab was only observed in patient 1 whose tumor has the lowest rate of PD-L1 expression. This may suggest that in RMC, response to PD-L1 inhibition therapy may not correlate with the rate of PD-L1 expression.

Conventional ossifying fibromas (OF) are benign, slow growing neoplasms, typically found in the gnathic bones, and thought to originate from the osseous mesenchyme or the periodontal ligament [1,2]. These tumors typically present in females in their third and fourth decade of life, with a propensity for the teeth-bearing areas of the mandible or maxilla [3]. Conversely, juvenile aggressive ossifying fibromas (JAOF) typically occur in the paranasal sinuses and craniofacial bones with rapid growth leading to local destruction, facial deformity, and associated complications. There are two histologic variants of JAOF: Juvenile trabecular ossifying fibroma (JTOF) and juvenile psammomatoid ossifying fibroma (JPOF). Both entities are rare in comparison to conventional ossifying fibroma and are indistinguishable on imaging. Therefore, clinical, radiologic, and pathologic correlations are required to reach the correct diagnosis. Herein, we present a case of juve-