Primary sclerosing epithelioid fibrosarcoma of the sacrum: a case report and review of the literature

Abstract

Sclerosing epithelioid fibrosarcoma is a rare tumour characterised histologically by a predominant population of epithelioid cells arranged in strands and nests, embedded in a fibrotic and hyalinised stroma. It is a low grade tumour with an indolent course. A 48 year old woman presented with a painful swelling over her back for six months. Investigation and biopsy revealed features of sclerosing epithelioid fibrosarcoma involving the left half of the sacrum, left sacro-iliac joint, and posterior part of the left ilium. Preoperative radiotherapy and wide location excision of the tumour were followed by metastatic recurrence of the tumour in the lung and scalp six years after initial presentation. The tumour showed typical histology of sclerosing epithelioid fibrosarcoma. The radiological features confirmed its primary location in the sacrum. The patient declined chemotherapy and died of disseminated disease eight years after initial presentation. Review of the literature confirms the fact that sclerosing epithelioid fibrosarcoma, despite its low grade, is a clinicopathologically distinct tumour with full malignant potential, the recurrence, metastasis, and mortality rate being 48%, 60%, and 35%, respectively. Sclerosing epithelioid fibrosarcoma can occur as a primary bone tumour, the clinical behaviour of which is probably similar to its soft tissue counterpart.

Figure 1

Computerised tomography scan of the patient, showing the tumour arising from the sacrum and involving the sacro-iliac joint and the posterior part of the ilium.

Figure 2

Multiple nodules are present in the chest radiograph, consistent with metastatic involvement of the lung.

Figure 3

(A) Cut surface of the tumour shows light yellow firm tissue. (B) Histologically, the tumour has a monotonous appearance, consisting of polygonal cells arranged in cords, strands, and clusters, surrounded by dense collagenous stroma with areas of hyalinisation. The tumour infiltrates into the surrounding cortical lamellar bone. (C) High power magnification to show the morphology of the tumour cells. They are rounded, oval, or polygonal, of small to medium size, and with clear or pale eosinophilic cytoplasm. The nuclei of the tumour cells are small, ovoid, or angular, and mostly pale or vesicular, with distinct nucleoli and little pleomorphism. (D) Some of the tumour cells show clear or vacuolated cytoplasm, but they constitute less than 20% of the tumour.