Pulmonary epithelioid inflammatory myofibroblastic sarcoma with multiple bone metastases: case report and review of literature

Abstract

Epithelioid inflammatory myofibroblastic sarcoma (EIMS) is a rare variant of inflammatory myofibroblastic tumor with distinctive morphological features and malignant clinical behavior. Only a few such cases have been described in the literature. We report here a case of unusual pulmonary EIMS with multiple bone metastases. A 21-year-old Chinese male patient presented with complaints of general fatigue and rapid weight loss, and a huge tumor arising in the left lower lobe of lung was detected by chest computed tomography. The mass of lung was totally resected. Microscopically, the tumor cells were rounded and epithelioid in shape. Myxoid stroma and inflammatory infiltration was also present. The tumor cells were immunopositive to anaplastic lymphoma kinase (ALK) in smooth cytoplasmic pattern. Fluorescence in situ hybridization (FISH) assay revealed the presence of rearrangement of ALK gene. Three months after lung surgery, there were multiple bone metastases and intraspinal mass found by positron emission tomography. The second surgical treatment was performed to remove the intraspinal lesion. The histological and immunohistochemical features of intraspinal mass were similar to those of pulmonary tumor. The diagnosis of pulmonary EIMS with multiple bone metastases was made. To the best of our knowledge, it may be the first case of an EIMS arising in lung. Awareness of EIMS in respiratory tract and its distinctive features is important for pathologists to avoid a diagnostic pitfall caused by histologic similarities to other ALK-positive tumors. ALK inhibitor is a promising treatment for this aggressive tumor regardless of its potential acquired resistance.

Fig. 1

Radiological findings of lung tumor and metastatic lesions of bone. a Chest computed tomography (CT) revealed a huge well-circumscribed mass in the left lower lobe of lung without signs of neighboring pleura invasion (white arrow). b The pulmonary tumor showed heterogeneous enhancement. Three months after surgery, F18-fluorodeoxyglucose (FDG) positron emission tomography revealed abnormally increased FDG uptake in the pelvic bone (c) and vertebra mass (d) (white arrows), indicating metastatic lesions of bones

Fig. 2

Postoperative micrographs of pulmonary and intraspinal masses. a Pulmonary tumor was non-encapsulated and observed to infiltrating the surrounding lung tissue. b In some areas of pulmonary tumor, the interlacing bundles of spindle cells were found to intermingle with plasma cells and lymphocytes. c The plump polygonal-like myofibroblasts with prominent nucleoli were also observed in myxoid background. d In other areas, the tumor was composed of diffused well-circumscribed polygonal and epithelioid tumor cells with distinct nucleoli. Nuclear atypia and mitotic figures were observed. e Necrosis could be found in epithelioid areas of pulmonary tumor. f The intraspinal tumor was composed of only polygonal and epithelioid tumor cells. a HE staining with original magnification × 100; b-f, HE staining with original magnification × 400)

Fig. 3

Immunohistochemical and FISH assay of tumor. The polygonal and epithelioid tumor cells were observed to be positive for Desmin diffusely (a) and ALK in smooth cytoplasmic pattern (b). c The spindle cells in pulmonary tumor were also found to be positive for ALK. However, the epithelioid tumor cells were negative for CD30 (d) and SMA (e) staining. f FISH assay with break-apart probe for ALK gene shows one intact yellow signal, one separated red and green signal per nucleus in tumor cells indicating the presence of a rearrangement of ALK gene. (a-e, immunohistochemical staining with original magnification × 400; f, FISH assay with original magnification × 400)