Popliteal mass in an adolescent girl
Introduction. An abnormal mass in the popliteal fossa can be caused by multiple pathologies, eg. a benign synovial cyst (Backer's cyst), tenosynovial giant cell tumor (TGCT), or an extremely rare pigmented villonodular synovitis (PVNS). The goal of this case report is to present an observed popliteal mass and overview its impact on the patient's health. Case Description. We report a 16-year-old girl presenting with right knee swelling, pain, limited joint movement. It started seven months ago, and worsened after visiting a sauna. The examination revealed swelling on the knee joint and a hard palpable structure in the poplitea, red vertical skin striae were visible around the mass. An ultrasound of the joints showed severe effusion in the suprapatellar bursa, synovial hypertrophy, a massive Backer's Cyst in the poplitea with multiple visible septa. MRI examination identified an increased fluid in the knee joint, significantly thickened synovium and Backer's cyst measuring approximately 10x5.8x3.2 cm. The patient underwent arthroscopy of the right knee. A cytological examination of the synovial fluid showed groups of synovial cells, average amount of leukocytes, lymphocytes (70%), neutrophils (30%), macrophages. Histologically - a tumor was found, formed by monomorphic cells with oval nuclei, eosinophillic cytoplasm, osteaoclast-type multinucleated giant cells, hemosiderophages, in line with the diagnosis of tenosynovial giant cell tumor. Summary. A female patient, diagnosed with a rare and benign TGCT, involving the synovium, bursae and tendon sheath. TGCT leads to joint pain, swelling and limitation of movement. The tumor was removed during an arthroscopy. Conclusions. We detected a non-malignant TGCT involving the joint synovium, bursae and tendon sheaths. Our patient underwent surgery - the most effective treatment for giant cell tumors.