FINAL DIAGNOSIS GLOMUS TUMOR OF THE KIDNEY
Glomus tumors arise from the glomus body, a specialized smooth muscle-derived structure that regulates blood flow for thermal regulation . Approximately 10 percent of glomus tumors are multiple, and in some instances, they are familial . Most patients with glomus tumors are young to middle aged adults . These lesions typically occur as painful skin nodules in the upper extremities, most often the subungual region of the fingers, followed by other portions of the distal extremities including the wrist, palm, and foot as the most common sites. Internal locations such as mediastinum, lung, trachea, and stomach are unusual for involvement by glomus tumor [3, 4]. Glomus tumor arising within the kidney is exceptionally rare, with six cases described .
The histologic differential diagnosis of glomus tumor of the kidney includes other neoplasms with myoid or pericytic differentiation (hemangiopericytoma, juxtaglomerular cell tumor, leiomyoma, and angiomyolipoma), neuroendocrine tumors (carcinoid tumor and paraganglioma) and metanephric adenoma. Histologic features and a panel of immunohistochemical stains differentiates glomus tumor from these entities.
Glomus tumor can have a hemangiopericytoma-like vascular pattern. However, hemangiopericytomas are smooth muscle actin negative, unlike glomus tumor . Juxtaglomerular cell tumor presents in a much younger population than glomus tumor and virtually all patients are hypertensive due to the secretion of renin by tumor cells [7, 8]. Immunohistochemically, juxtaglomerular cell tumor can be separated from glomus tumor by strong renin and CD34 positivity and focal patchy staining of smooth muscle actin . Ultrastructurally, renin-specific granules are present.8 Angiomyolipoma, with a predominant muscular component might enter the differential diagnosis but can be separated from glomus tumor by HMB-45 or melan-A positivity of the perivascular epithelioid cells . Although glomus tumors in which the cells form nests might be confused with paraganglioma, lack of chromogranin and synaptophysin expression clarifies the diagnosis. Leiomyomas, particularly the epithelioid variant can be a part of the differential diagnosis, but they are usually strongly desmin positive. Metanephric adenoma can be differentiated from glomus tumor by positive WT1 and S100 staining [10-12].
In conclusion, this lesion is difficult to distinguish from other renal neoplasms by radiographic imaging. Histologic and immunohistochemical overlap with other entities that occur in the kidney can lead to an incorrect diagnosis. Careful histologic examination and immunohistochemical interpretation are necessary to make the diagnosis of glomus tumor of the kidney, which shows an excellent clinical outcome.
Contributed by Kotaro Sasaki, MD, Sheldon I. Bastacky, MD, Anil V. Parwani, MD. PhD and Debra L. Zynger, MD