Primary intrarenal hemangioma - A series of 39 cases.

Intrarenal hemangiomas lack concise clinicopathologic information, due to the predominance of single case reports and inclusion of other vascular neoplasms and hemangiomas of perirenal, hilar, and renal vein origin. Herein, in this multi-institutional study we evaluate clinicopathologic features of 39 intrarenal hemangiomas. The median age was 62 years (range = 27-94 years; 2:1 male to female ratio), with left-sided predominance (left = 21, right = 13; one case was bilateral). The median tumor size was 1.5 cm (0.2-10 cm). Two cases arose from transplanted kidneys. Most were asymptomatic (n = 30, 86 %), even though most surgical interventions (19 partial, 19 radical, 1 biopsy) were due to hemangiomas (n = 24, 62 %). Synchronous renal neoplasms were present in 9 (23 %) patients, including clear cell renal cell carcinoma (RCC) (n = 4), angiomyolipoma (n = 2), oncocytoma (n = 2), and chromophobe RCC (n = 1). Multifocal hemangiomas (n = 5) were seen in cases with end stage renal disease. Intrarenal hemangiomas were mostly anastomosing (n = 18; 46 %), followed by capillary (n = 15; 38 %), and cavernous (n = 6; 16 %) subtypes. Fibrin thrombus (n = 9; 23 %) and extramedullary hematopoiesis (n = 4; 10 %) were occasionally present, the latter being only in the anastomosing subtype. Immunohistochemistry was performed on a majority (n = 33, 84 %) of hemangiomas, with vascular markers CD31 and CD34 and lack of PAX8 were most used for diagnosis. 30 patients had follow-up (median 48 months, range 1-241 months), none showed disease progression/recurrence. This study provides comprehensive observation of the largest intrarenal hemangioma cohort, highlighting their frequent cause of surgical intervention when present, predominance of anastomosing subtype, multifocality in end stage kidney disease, and occasional concurrent ipsilateral neoplasms.