Glomus Tumor of Hoffa's Fat Pad and Its Management by Arthroscopic Excision
A 42-year-old woman presented to us with a history of pain in her right knee for the past one year. The trigger spot for the pain was located just medial to the ligamentum patellae at the level of the joint line. The pain was sharp and shooting in nature and was precipitated by pressure over the trigger spot. The patient was very apprehensive and would not allow repeated examination due to the fear of precipitating the severe pain. The patient was also unable to squat or sit cross legged since deep knee bending would also precipitate the pain. There was no history of aggravation of pain with change in the temperature. She had visited numerous local physicians for the past one year, but despite the dramatic presentation, no diagnosis had been made in the patient till then. Her inflammatory parameters (cell counts, 7,800; erythrocyte sedimentation rate [ESR], 10 mm 1st hour) were normal. A radiograph of the knee was normal. Magnetic resonance imaging (MRI) of the knee revealed a 1 × 1 cm nodule at the inferior aspect of the patella in Hoffa's fat pad. This nodule was hyperintense on T2-weighted images and hypointense on T1-weighted images (). A characteristic clinical picture along with supportive MRI findings led us to suspect glomus tumor as a possible diagnosis. An ischemia test was done at this stage and was found to be positive, and it substantiated our diagnosis. Due to the intraarticular nature of the nodule, no attempt was made to infiltrate it with local anaesthetic.\nThe patient was taken up for arthroscopy of the right knee under a tourniquet. Standard anterolateral and anteromedial portals were used. Intraoperatively, a pedunculated 0.8 × 0.5 cm reddish brown nodule arising from Hoffa's fat pad was seen. A 70° scope was also used to inspect the fat pad. The reddish brown color of the nodule made it easy to differentiate from the surrounding yellow fat pad (). The fat around the pedunculated nodule was carefully shaved to reveal the base. The nodule was excised from the base and the tissue sent for histopathological examination. No separate incision or portal was required to remove the nodule. The fat pad was inspected again and parts of the surrounding synovium were removed to ensure complete removal and decrease the chances of recurrence.\nThe histological evaluation confirmed the diagnosis of glomus tumor. H&E staining () revealed a well-circumscribed, encapsulated lesion composed of hyalinized variably sized blood vessels lined by flattened endothelium with the perivascular region showing a solid proliferation of monomorphic round to oval cells with fine chromatin, inconspicuous nucleoli and moderate cytoplasm. A further confirmation was made using immunohistochemisty for smooth muscle actin which showed diffuse cytoplasmic positivity ().\nPostoperatively the patient had dramatic total relief from pain and she remains asymptomatic at the last follow-up after 15 months.