Primary giant cell tumor of soft tissue in the finger
1. Department of Dermatology, Hospital "Infanta Margarita," Cabra,
Córdoba, Spain. firstname.lastname@example.org
Primary giant cell tumor of soft tissue (GCTST) arising in a finger is a rare event. We report a case of a 54-year-old man with a primary finger giant cell tumor that appeared histologically identical to giant cell tumor of bone. The patient presented with a cystic mass of the finger. The magnetic resonance imaging showed no relation between the nodule and bone, tendons or synovial tissues. The distinction of this entity from other more common primary finger tumors with giant cell morphology is emphasized.
A 54-year-old man presented with a 2-year-history of a lump at the base of the distal phalanx of the right ring finger. The patient denied any direct trauma to this area. Physical examination showed a 12-mm diameter nodule with a cystic aspect. The skin over the nodule was normal with no surface change and the nodule was not fixed to the underlying tendons (Fig. 1). The magnetic resonance imaging study showed no relation between the nodule and bone, tendons or synovial tissues. A clinical diagnosis of epidermoid cyst was made. Under ring block anaesthesia the lesion was completely removed.
On gross examination, the lesion was a well-outlined, solid, round mass. Microscopically, the tumor consisted of a non-encapsulated, well-circumscribed mass in the subcutaneous tissue composed of large nodules of cells that extended to the reticular dermis. The neoplastic cells were ovoid to spindle with vesicular nuclei forming a syncytium. These cells were admixed with numerous osteoclast-like giant cells (Fig. 2). Cytological atypia and mitotic activity were not prominent. In some areas, the tumor matrix exhibited a chondroid (Fig. 3) and osteoid pattern (Fig. 4). No focal areas of hemorrhage, foamy macrophages, fibrohistiocytic changes or vascular invasion were seen. Immunohistochemistry showed the multinucleate cells stained positive with CD68. Staining for CD45, cytokeratin (AE1-AE3), smooth muscle actin, S-100, CD31 and lysozyme were negative. These findings were consistent with the diagnosis of GCTST. There has been no recurrence in the 18 months since the operation.
Primary giant cell tumor of soft tissue (GCTST) is a rare soft tissue tumor originally described in 1972 in 2 different series by Salm and Sissons  and Guccion and Enzinger . The lesion affects patients aged between 5-84 years, with no predilection for sex . It commonly involves the thigh, trunk, and upper extremities. Although the histogenesis of GCTST is uncertain, its histologic features are similar to giant cell tumor of bone.
Histologically, GCTST shows a well circumscribed, non-encapsulated and multinodular lesion, composed of round to spindle-shaped cells intimately admixed with scattered osteoclast-like multinucleated giant cells. It has been postulated that the osteoclast-like cells arise by fusion of the mononuclear cells . Chondroid, osteoid or mature bone is present in approximately 50 percent of cases, usually located at the periphery of the tumor. Immunohistochemically, GCTST stains for CD68, vimentin and tartrate-resistant acid phosphatase. Cytokeratin, smooth muscle actin and S-100 immunoexpression have also been reported . The prognosis of GCTST was initially thought to be that of a malignant tumor, based on the aggressive histologic appearance and clinical behavior exhibited by the reported tumors . The metastatic potential was mainly related to deep invasion . However, some of the originally reported tumors were similar to "malignant fibrous histiocytoma." More recent studies have established other histologic criteria for the diagnosis of GCTST, more similar to conventional giant cell tumor of bone. According to these criteria, the tumors have a better clinical course and the depth of the lesion does not appear to be a significant prognostic factor [3, 5].
The differential diagnosis of GCTST includes soft tissue mesenchymal tumors that are rich in giant cells, especially nodular tenosynovitis. This would be a consideration in the present case because of the tumor location on the hand. Nodular tenosynovitis (giant cell tumor of the tendon sheath) is encapsulated, shows a characteristic nodular growth pattern, lacks the typical spindle stromal cells of a conventional giant cell tumor, and contains scattered giant cells, lymphocytes, foamy macrophages, hemosiderin and large amounts of dense fibrous tissue. These features are scarce or absent in GCTST. Immunohistochemically, nodular tenosynovitis stains for CD68 and CD45, without lack of smooth muscle actin immunoreactivity . A soft extension of an underlying giant cell tumor of bone must be ruled out by clinical and radiological evaluation. Other benign lesions include pigmented villonodular synovitis, which affects synovial lined joints, bursae and tendon sheaths. This is characterized by the presence of hemosiderin-laden multinucleated giant cells. The ubiquitous presence of hemosiderin lends the tissue a characteristic pigmented appearance. Nodular fasciitis with osteoclast-like giant cells are composed of immature fibroblasts in short, irregular bundles. Giant cells surround areas of hemorrhage and myxoid degeneration. Cellular dermatofibroma shows a commonly fascicular growth pattern, a predominance of eosinophilic spindle cells, and focal cytologic polymorphism with inflammatory cells, foamy cells and giant cells.
Malignant giant cell tumors of soft tissues may be the malignant counterpart of the neoplasm described here. Giant cell malignant fibrous histiocytoma, osteoclast-like giant cell rich leiomyosarcoma, and extraskeletal osteosarcoma are usually large, deeply-seated lesions with obvious cellular atypia. In contrast, GCTST is frequently superficial and devoid of significant pleomorphism and atypical mitosis. Epithelioid sarcoma may be considered because of the presence of osteoclast-like giant cells in some of these tumors. Epithelioid sarcoma shows larger tumor cells, zones of central necrosis, and a more infiltrative pattern. In other areas of the body, atypical fibroxanthoma may be considered. This tumor is a sun-induced lesion sometimes containing osteoclast-like giant cells, but it has a cellular pleomorphism and atypical mitosis, features lacking in GCTST. Plexiform fibrohistiocytic tumor is another sarcoma that should be included in the differential diagnosis. This lesion primarily affects the distal upper extremity of children and young adults. It consists of a mixture of histiocyte-like cells and multinucleated giant cells arranged in a plexiform pattern. Primary GCTST lacks the plexiform pattern and smaller nodules of this tumor.
The optimal treatment of GCTST appears to be conservative surgical resection with tumor-free margins. A careful follow-up of these patients is necessary because of the possible malignant potential of the tumor.
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