Challenges in diagnosis: Lesions following needle injury that mimic tenosynovial giant cell tumor

Tenosynovial giant cell tumors (TSGCTs) are the second most common type of tumor found on hands after ganglion cysts. In contrast to the painful nature of a ganglion cyst, a TSGCT is painless. It is predominantly benign in nature. Clinically, there are mainly three types of TSGCTs: localized, diffuse, and malignant. Although this is a well-established entity, diagnosis remains challenging and encompasses a wide differential diagnosis. Our aim in reporting this case is to demonstrate how a simple needle injury can mimic this entity and lead to diagnostic dilemmas. To the best of our knowledge, no similar case has been reported in the medical literature. We present the case of 35-year-old female patient who developed localized swelling because of an iatrogenic needle prick that involved a nerve bundle and caused the patient extreme pain. Upon clinical, radiological, and histological examination, this lesion resembled a TSGCTs and led to a misdiagnosis. However, after synthesizing all relevant information, particularly the clinical history of the needle injury, the conclusive diagnosis favors a foreign body giant cell reaction accompanied by granulomatous inflammation. In this case review, we emphasize several key points that differentiate this entity from those in similar differential diagnoses. This case underscores the importance of a multidisciplinary approach to diagnosis, integrating clinical, radiological, and histomorphological features. • TSGCTs are benign tumors from synovial tissue, with three types: localized, diffuse, and malignant. • A 35-year-old female developed swelling and severe pain in her thumb after an iatrogenic needle prick, initially misdiagnosed as TSGCT. • Accurate diagnosis requires a combination of clinical history, radiological findings, and histopathological examination. • Histopathology revealed granulomas and various giant cells, inconsistent with typical TSGCT features. • The patient's trauma history was crucial for diagnosis in similar cases.