Abdominal giant cell tumor of soft tissue: A case report with diagnostic pointers

INTRODUCTION

Giant cell tumor of soft tissue (GCTST) is a primary soft tissue neoplasm with rare incidence. Salm and Sissons first described this entity in 1972; the tumor was initially considered a benign neoplasm with histological similarities to the giant cell tumor of bone.^[1] Guccion and Enzinger reported a more aggressive form of the tumor, making its biological behavior potentially malignant.^[2] Oliveira et al. reported cases with metastasis, identifying it as the behavior of a low-grade sarcoma.^[3]

Oliveira et al., and Folpe et al., reported that complete surgical excision may be potentially curative for GCTST.^[3,4] Lee et al. reported a distinct pathogenetic difference between GCTST and GCT of bone, as the former lacked the H3F3A genetic mutation seen in GCT of bone.^[5]

GCTST is commonly reported in the upper and lower extremities, with an equal gender preponderance and average age of presentation at 40 years. Case reports have documented rare sites for GCTST, including head and neck, trunk, colon, breast, axilla, and liver.^[6-10]

The present case report describes clinico-pathological features of GCTST in a 36-year-old female with the tumor arising in the abdominal wall, which is an unusual site for such a neoplasm.

CASE REPORT

A 36-year-old female patient presented with an abdominal mass in the right lumbar region. It was non-tender and indolent in growth over the past 6 months. Ultrasonography showed a hypoechoic area measuring approximately 28 × 27 mm, with a suspicion of a benign lesion. The patient underwent a wide local excision of the swelling. Pathological examination showed a grey-brown nodular tissue measuring 4.0 × 3.0 × 1.5 cm with peripheral calcification. Microscopy revealed a tumor with peripheral metaplastic trabecular bone surrounded by new bone formation with osteoblastic rimming [Figure 1]. Sheets of mononuclear cells with round to oval nuclei, some showing spindle cell morphology and scant eosinophilic cytoplasm, and abundant osteoclast-like giant cells [Figure 2]. The tumor cells lacked nuclear atypia or necrosis. Mitotic figures were 3-4 per 10 high-power fields. There were foci of cartilage matrix along with peripheral bundles of skeletal muscle and fibroadipose tissue. The peripheral margins were clear of the tumor. Based on the findings, a diagnosis of a GCTST was made. Clinical and radiological correlation was advised to assess any potential spread or organ involvement. The available follow-up data show a disease-free period of 6 months.

Close

Figure 1: Peripheral metaplastic bone formation seen, with osteoblastic activity, enclosing the lesion (Hematoxylin and eosin, 40x).

Export to PPT

Close

Figure 2: Tumor with sheets of monomorphic oval to spindle cells with numerous interspersed osteoclast-like giant cells (Hematoxylin and eosin, 100x).

Export to PPT

DISCUSSION

GCTST is a rare neoplasm with a low malignant potential. Most of the documented literature described the predilection for the upper and lower extremities. The average age of presentation is 40 years, and there is an equal gender preponderance.^[11] Rare case reports of GCTST have been documented at other sites, including head and neck, trunk, breast, and colon. Clinical presentation of the lesion is varied and depends on the site of occurrence; however, they are reported to have an indolent growth pattern. Luangxay et al.^[7] reported the case in the breast, and Lee et al.^[10] reported the case in the colon. Yadav et al.^[12] reported it in the abdominal wall of a 28-year-old female. The present case of GCTST involved the abdominal wall, with a swelling arising and attached to the rectus fascia in a 36-year-old female. The literature search reveals this to be the second documentation of GCTST in the abdominal wall.^[7,10,12]

GCTST has an identical histological presentation to GCT of bone with sheets of mononuclear cells and abundant osteoclast-like giant cells. They can have a rim of metaplastic bone at the periphery, which may extend to the center. The tumor may show secondary aneurysmal bone cyst-like changes. They can be multilobulated and show extension into the surrounding soft tissue. The major differential diagnosis of the entity includes GCT of bone and tenosynovitis tissue, which can be ruled out based on radiological features and involvement of bone and joints. GCTST can show metastasis and even vascular invasion, which warrants a careful examination to rule out soft tissue malignancies with giant cells, such as leiomyosarcoma, pleomorphic sarcoma, and melanoma. The absence of nuclear atypia and low mitotic activity can help exclude the differential diagnosis.^[12]

Immunohistochemistry is of limited value in the diagnosis. GCTSTs are positive for vimentin, CD68, smooth muscle actin, and p63 and negative for S100, CD45, H3.3G34W, which can help in difficult cases [Table 1].^[12,13]

Surgical excision with clear margins is the treatment of choice for GCTST. Cases of post-surgery radiotherapy have been documented in patients with incomplete resections. The recurrence rate of GCTST is reported to be 10-15% with a few cases showing metastasis. The presented case was treated with surgery, and post-surgery radiotherapy was not advocated in view of clear margins. The local recurrence rate makes a long-term follow-up imperative.^[11-13]

CONCLUSION

GCTST is a rare but important tumor to consider in soft tissue masses. Although the cancer has a low malignant potential, regular follow-up and monitoring are necessary due to the risk of recurrence. The present case is reported for the rarity of the site, adding to the existing literature.