Clinical findings included patient age, location, physical examination, and patient history. In case 1, a 60-year-old man was referred to our department for evaluation of a painless, slow-growing right-sided mass on the thigh next to the inguinal flexure. Physical examination revealed a 4.0x2.0cm firm, poorly circumscribed and non-movable mass. There was no history of fever, injury and skin redness. Laboratory data, including calcium, phosphate and alkaline phosphatese values, were all within the normal ranges.
In case 2, a 36-year-old woman was admitted to our hospital with swelling, skin redness and pain in the upper limb that persisted for 6 months without prior history of trauma. A clinical examination revealed that the 6.0x4.0cm mass lesion was tender and did not display any discharge or drainage sinus. No lymph node metastasis was found in any case, and both cases showed no evidence of metastasis or recurrence at half to one-year follow up.
Both patients underwent US and CT scan. For case 1, US revealed a well-circumscribed large solid mass located in the gracilis muscle. The Doppler sonographic examination showed a few vascular signals within the mass (Fig. 1a). Plain CT showed an isodensity mass with enlargement of gracilis muscle, while contrast CT revealed a slightly persistent homogeneous enhancement of the mass with blurred margins (Fig. 1b-d). For case 2, US revealed a blur large solid mass located in the deltoid muscle. Plain CT showed a hypodensity mass located in the superficial deltoid muscle extending to the intermuscular space, while contrast CT revealed a slightly persistent heterogeneous enhancement of the mass with blurred margins (Fig. 1e-f). There were no evidences of calcification or mineralization in any of the mass, and the adjacent structures were all normal.
On MRI, the morphological manifestations of the masses were showed intuitively. The maximum lesion size ranged from 4.0 cm to 6.0cm. All lesions showed iso-hyper signal intensities on T2WI with fat saturation (Fig. 2a, white arrow) or without fat saturation (Fig. 3a white arrow) sequence, and heterogeneous hypo-iso signal intensities on T1FSPGR sequence (Fig. 2b, white arrow; Fig. 3b white arrow), relative to muscle signal intensity. The solid masses showed well-defined margins adjacent to the subcutaneous tissue, while the blurred margins adjacent to the muscle showed a slight hyperintense signal on T2-weighted images (Fig. 2c, black triangle). On DCE-MRI, all lesions showed single or multiple nodular enhancements with either oval (Fig. 2d white arrow) or irregular (Fig. 3c) shapes, and with blurred margins. Furthermore, internal enhancements were all heterogeneous. TIC appeared with a slow increase type (Fig. 3d). Lesions on DWI (b=500s/mm2) were hyperintense with an higher mean ADC value of 2.19× 10−3 mm2/s (Fig. 3e, ROI 3) than surrounding normal soft tissue (1.03× 10−3 mm2/s)(Fig. 3f, ROI2).
The resected specimens revealed that the tumors invaded the peripheral muscles. Consequently, complete surgical excision of the mass was performed. Pathological examination indicated that many multinucleated giant cells were scattered, and were surrounded by spindle cells, which suggested a GCT-ST. The giant and spindle cells had slight cellular atypia. In addition, spindle cells exhibited brisk mitotic activity. The tumor invaded the neighboring muscles in both cases. The obtained data suggested that this was a slow-growing entity.
Tumors interstitial hemorrhage were obvious and rich in hemosiderin-containing cells (Fig. 4 a-d). Immunohistochemically, the giant cells were strongly positive for CD68 in both cases. In addition, compared to Case 2, smooth-muscle actin (SMA) of Case 1 showed focally positive staining. In addition, no staining of Myoglobin, Myogenin, MyoD1, desmin, CD34, S-100, CK and EMA were found in both tumors (Fig. 4 e-f). Finally, based on clinical, histologic and immunohistochemical (IHC) findings, patients were diagnosed with giant cell tumors.