LAUSR

Glomus tumours are neoplasms of mesenchymal origin, first described in 1924 by Masson. These tumours resemble the modified smooth muscle cells of the glomus body which helps regulate body temperature and blood pressure. They are most commonly found in the deep dermis or subcutaneous tissues of the extremities, especially the subungual region. Glomus tumours have also been described in stomach, small bowel, rectum, urinary tract, lung, cervix, vagina, mediastinum, trachea, oral cavity, bone, mesentery, heart and lymph nodes. Renal glomus tumours are extremely rare, with only eight reported cases of primary renal glomus tumours reported in the literature. A 66‐year‐old man presented with an incidental finding of a right renal mass on ultrasound while being investigated for an elevated prostate-specific antigen. He had no history of lower urinary tract symptoms, haematuria or flank pain. He is a healthy and active bus driver with a history of asthma and mild urticaria. He also has a 40‐ pack year history of smoking. Physical examination was unremarkable with no palpable masses in the right flank. Computed tomography scan showed a rounded, heterogenous mass in the upper pole of the right kidney (Fig. 1). Renal ultrasound showed a 5-cm complex echogenic mass with solid and cystic components as well as internal and peripheral vascularity. The patient subsequently underwent a right radical nephrectomy. Macroscopically, the mass was located within the cortex of the upper pole of the right kidney, measuring 58 × 55 × 47 mm. It was a well circumscribed, nodular, multicystic tumour which was contained within the renal capsule (Fig. 2). Microscopic features included vessels of variable size, sheets and nests of bland cells with round to oval nuclei and a moderate amount of eosinophilic cytoplasm. There was no mitotic activity. Entrapped tubules were present at the periphery of the lesion. Centrally there were areas of tumour infarction but no necrosis was identified (Fig. 3). Confirmatory immunoperoxidase stains were performed with the tumour cells showing staining for SMA and focal GATA3. There was no staining within the tumour cells for PAX8, p40, pan cytokeratin, CK19, CK7, CK5/6, AMACR, EMA, MUC‐4, ERG, CD56, chromogranin, synaptophysin or desmin. These micro and macroscopic pathological features and staining patterns are consistent with a primary glomus tumour. Glomus tumours account for less than 2% of soft tissue tumours, with 25% of these arising in visceral organs where glomus bodies are not found. They contain a mixture of glomus cells, blood vessels and smooth muscle cells. Depending on the prevalent cell type, the tumours are classified as solid glomus tumours, glomangioma or glomangiomyoma. The most common site of occurrence is the subungual region of the finger, where they develop as small blue‐red nodules. Glomus tumours have also been described in oesophagus, mediastinum, lung, stomach, colon and urinary bladder. Only eight cases of glomus tumours of the kidney have been reported to date. Billard et al. described a glomangiomyoma involving the renal capsule, while Siddiqui et al. described a glomangioma of the renal parenchyma. In a case series by Al‐Ahmadie et al., three cases of glomus involving the renal parenchyma were described. Herawi et al. described a solid glomus tumour involving