Plexiform xanthomatous tumor: a report of 20 cases in 12 patients

We present 12 patients with 20 plexiform xanthomatous tumors (PXTs). All patients were male. Patient ages ranged from 20 to 59 years (mean 45 years). Clinical information was available for 11 (92%) patients. Only one patient with markedly elevated cholesterol levels had a family history of hypercholesterolemia; none of the others had a family or personal history of diabetes mellitus, hypercholesterolemia, or hyperlipoproteinemia. Three patients had markedly elevated serum triglyceride levels. The tumors were solitary in seven patients and multiple in five patients: three patients had two tumors, one presented had three, and one had four. PXTs were located on the knee (n = 8), elbow (n = 5), foot or hand (n = 3), and one each on the Achilles tendon, buttock, toe, and back. PXT was white to yellow in color and ranged in size from 0.7 to 5 cm (mean 2.7 cm). The tumors were located in the dermis and subcutis, had a distinctive plexiform arrangement, and were composed of various admixtures of uniform epithelioid and xanthomatous cells. All tumors in patients with solitary or multiple lesions had a plexiform architecture. Most of the nodules of the plexiform pattern of PXTs measured 0.5-2 mm. Rarely cholesterol clefts, necrosis, sparse inflammation, and multinucleated Touton giant cells were present. In two patients with multiple tumors, the PXT completely lacked the xanthoma cells and thus resembled an epithelioid lesion. Immunohistochemically, all lesions were KP1 (CD68) and vimentin positive and lysozyme, S-100 protein, HMB-45, epithelial membrane antigen, cytokeratins, factor VIIIrag, CD34, muscle-specific actin, alpha-smooth muscle actin, desmin (D33), desmin (Der-11), chromogranin, synaptophysin, neurofilament protein, and glial fibrillary acidic protein negative. Two patients with multiple lesions noted recurrences over 10 years. With the exception of one patient who died of an unknown cause, all 10 patients with follow-up were alive, some with residual disease, over a mean of 9 years (range 1-25 years). Some PXTs may represent a morphologic variant of tuberous or tendinous xanthoma, yet its exclusive occurrence in men, absence of personal/familial hyperlipemia/hypercholesterolemia in some patients, and relative paucity of inflammation and cholesterol clefts may make this a distinctive entity.