Giant Cell Tumor of Tendon Sheath: A Rare Peri-carpo-metacarpal Location Masquerading as a Recurrent Ganglion Cyst-a Diagnostic Conundrum

INTRODUCTION: Giant cell tumors of tendon sheath (GCTTS) are benign soft-tissue lesions commonly affecting the digits, which occasionally cause pressure atrophy of an adjoining bone; but perforating the cortex to expand into the medullary canal is quite uncommon. We report such a case of suspected recurrent ganglion cyst with eventually manifested as a GCTTS with an intra-osseous involvement of the capitate and hamate bone. CASE PRESENTATION: A 28-year-old lady had been diagnosed as a case of recurrent ganglion cyst of the dorsum of the left wrist – 6 years ago and 4 years ago – both of which were confirmed histopathologically and were surgically excised. The patient had now presented in July 2021 with similar complaints of pain and swelling over the same site, for 1 year. Our initial clinical diagnosis was a case of recurrent ganglion cyst. Patient also presented with occasional bouts of fever for the past 2 weeks, which made us suspect osteomyelitis as well. Routine blood parameters showed that an elevated ESR and CRP, blood, and urine cultures were negative and magnetic resonance imaging showed features suggestive of osteomyelitis-involvement of capitate and hamate bone. However, to our surprise, intraoperatively, there were no features suggestive of osteomyelitis and the lesion was excised in-toto and the gross specimen resembled a classic ganglion cyst, which was sent for histopathological examination. To our surprise yet again, it was reported as a case of Giant cell tumor of the tendon sheath, which in retrospect, clinically and radiologically correlated with an intra-osseous involvement of the capitate and hamate. The patient is on regular follow-up to pick up any further recurrences. CONCLUSION: “Once a ganglion, always a ganglion” should not be taken as the Gospel truth. Histopathological diagnosis continues to remain as the gold standard, especially in cases of soft-tissue swellings of the hand. Correlation and integration of clinical features, Imaging modalities and histopathological diagnosis are the cornerstone in the management of GCTTS.