P3.M243: Beyond a Sprain: An Unusual Presentation of Bone Pain in a 16 -year-old Male

Introduction: Bone pain is one of the most common complaints in children. Although it's mainly secondary to a benign cause, it could also be the primary symptom to a more serious condition such as malignancy. Most benign conditions such as bone tumors are asymptomatic and diagnosed incidentally; however others can present with pain, swelling and other systemic symptoms. The overlap in symptoms in both benign and malignant processes make diagnosis challenging. Thorough evaluation including combination of multiple findings on physical exam and imaging can help narrow down the diagnosis.

Case Description: A previously healthy 16-year-old male presented with 3-month history of right ankle swelling and weight bearing pain after playing on a trampoline. At the time, he was seen by orthopedics and placed on a walking boot for a month. He presented again to orthopedics with persistent pain. MRI obtained showed an infiltrative bone lesion of right calcaneus with surrounding enhancing soft tissue mass concerning for neoplasm. He underwent 2 biopsies which were non diagnostic. While awaiting the second biopsy result, PET scan was done showing abnormal hypermetabolism in the right calcaneus lesion associated with lymph nodes in the right popliteal and inguinal regions. He then presented with growing right inguinal lymph node; ultrasound obtained showed findings concerning for metastatic disease. He ultimately underwent lymph node excision and biopsy which revealed diffuse large B-cell lymphoma, stage II; started on chemotherapy under protocol ANHL 1131.

Discussion: Lymphomas usually occur in the lymph nodes with extra nodal site being less frequent. Primary bone lymphoma (PLB) is a rare type of lymphoma that accounts for 3-7% of primary bone tumors. The presentation usually includes bone pain, palpable mass and bone fractures with B symptoms seen less commonly. In our patient the combination of persistent pain not attributed to trauma, swelling and association with enlarged lymph node prompted further evaluation. Imaging is typically the first initial approach. MRI can help distinguish primary lymphoma of the bone from other bone tumors such as Ewing sarcoma and osteosarcoma. However, microscopic features aid guide final diagnosis for accurate treatment. In our case despite inconclusive biopsies, worsening symptoms ultimately led to lymph node excision and final diagnosis.

Conclusion: Identifying warning signs is key for early referral to pediatric oncologist. Although bone pain mainly accounts for benign conditions, recognizing additional findings on exam, course and length of symptoms in association with abnormal imaging can help prevent delay in diagnosis and increase possibility of successful treatment.