Background

This rare soft tissue tumor and presents as a congenital tumor or in early infancy. Less than 5 cases have been described. These tumors have been described in the palate, scalp, and hand. All tumors were ulcerated and may infiltrate the surrounding soft tissue and bone.

INCIDENCE	Very rare
AGE RANGE-MEDIAN	Congenital or early infancy

HISTOLOGICAL TYPES	CHARACTERIZATION
General	Common striking feature are nodular, linear, and plexiform aggregates of oval-to-spindle cells with pink flocculent cytoplasm and round, reniform, or spindle nuclei with dispersed chromatin, small nucleoli, and occasional mitoses Within these aggregates were large mononucleate cells and multinucleate giant cells with one to several nuclei, often with prominent nucleoli, and abundant granular eosinophilic cytoplasm Round conglomerates of oval-to-spindle cells and giant cells mimicked non-necrotizing granulomas Some aggregates had discernible lumens, either empty or containing erythrocytes, lined by plump, cuboidal, or flat endothelial cells Concentric arrangement of oval-to-spindle cells around small-caliber vascular structures resulted in an onion skin appearance Envelopment of preexisting blood vessels rarely was observed Occasional vessels showed eccentric periendothelial proliferation protruding into the lumen Perineural and intraneural involvement by small vessels was common In some regions, stroma between the tumoral aggregates was loose, and moderate lymphoplasmacytic infiltrate and scattered mast cells were present Periphery of the lesions, increase in vessels of capillary or slightly larger size, with plump endothelial cells and generally one or two layers of periendothelial cells Vessels were separated by a loose stroma containing delicate spindle cells
VARIANTS

SPECIAL STAINS/IMMUNOPEROXIDASE/OTHER	CHARACTERIZATION
Special stains
Immunoperoxidase	Factor VIII and CD31 was positive in the endothelium of lesional and nonlesional vessels Highlighted poorly discernible, small vascular channels within the densely cellular areas Oval-to-spindle cells in the aggregates and periendothelial cells in the hemangioma-like areas showed strong positive staining for smooth muscle actin and vimentin Strong positive staining for KP-1 antibody in the multinucleate giant cells and large mononucleate cells Weakly positive staining for peanut lectin agglutinin in some of the multinucleate giant cells Negative for: Desmin, S-100, LCA, EMA, and Cam 5.2

DIFFERENTIAL DIAGNOSIS	KEY DIFFERENTIATING FEATURES
Giant cell fibroblastoma	Express CD34 and show rearrangements of chromosomes 17 and 22
Epithelioid hemangioendothelioma with osteoclast-like giant cells	Am J Clin Pathol 1990;93:813?. Arch Pathol Lab Med 1993;117:315?. Young adults Epithelioid tumor cells in these cases, even in solid areas, recapitulated endothelial cells with intracytoplasmic lumina and Factor VIII staining Lack the concentric orientation of cells around small vessels
Plexiform fibrohistiocytic tumor	Children and young adults and is characterized by the plexiform and nodular growth of rounded histiocytoid cells with interspersed osteoclast-like giant cell Onion-skin layering of tumor cells around vessels and the hemangioma-like areas are absent
Myopericytoma	Am J Surg Pathol 1998;22:513?5. Cells with pericytic/myofibroblastic differentiation in a concentric arrangement around vascular lumens Hemangiopericytoma-like areas Giant cells were not described in cases of myopericytoma Found mainly in adults, youngest patient was 10 years old
Infantile myofibromatosis, infantile fibromatosis, or infantile fibrosarcoma	Oncology Reports 1999;6:1101?. Am J Surg Pathol 1994;18:14?4. Characteristic chromosomal aberrations have been described

PROGNOSIS AND TREATMENT	CHARACTERIZATION
Prognostic Factors	Natural history of giant cell angioblastoma is not fully known Features typically associated with malignancy, such as a brisk mitotic rate, anaplasia, and necrosis are absent in giant cell angioblastoma The clinical features, histological findings, and follow-up data suggest that giant cell angioblastoma is a benign tumor that would not be expected to metastasize but that could create significant local problems because of its infiltrative nature.
Treatment	Am J Surg Pathol 1991;15:175?3. This tumor extensively infiltrated the skin, soft tissue, and bone of the entire forearm-managed with amputation when the patient was 3 months old
	Am J Surg Pathol 2001;25:185-196 With interferon- therapy one had no progression of residual microscopic disease Second patient experienced considerable regression of the tumor with interferon- administered before subtotal excision-currently has stable minimal residual disease

Am J Surg Pathol 1991;15:175?3.
Am J Surg Pathol 2001;25:185-196