Thoracic epithelioid inflammatory myofibroblastic sarcoma: a rare and aggressive disease with case report and literature review

Abstract

Epithelioid inflammatory myofibroblastic sarcoma (EIMS) is a rare subtype of inflammatory myofibroblastic tumor, characterized to be an aggressive disease with high frequency of ALK rearrangement, rapid recurrence, and poor prognosis. Primary EIMS of thoracic origin is rarely observed. Herein, we described a case of 28-year-old female developed primary EIMS in the anterior mediastinum with hepatic metastasis. The EIMS displayed sheet-like growth of epithelioid and spindle cells with enlarged nuclei, abundant and eosinophilic cytoplasm, and infiltration of inflammatory cells. Immunohistochemical staining revealed positive expression of ALK in the nuclear membrane, and ALK rearrangement was identified by polymerase chain reaction assay. Alectinib showed partial response, and achieved a meaningful survival benefit for four months. Based on this case report and literature review, ALK inhibitor reveals promising activity on the rare but aggressive EIMS. Awareness of EIMS in thoracic disease and its clinicopathological features is essential to avoid erroneous diagnosis.

Keywords: ALK rearrangement; Alectinib; Epithelioid inflammatory myofibroblastic sarcoma; Inflammatory myofibroblastic tumor; Thoracic.

Fig. 1

Computed tomography images of thoracic EIMS in the anterior mediastinum, associated with hepatic metastases at baseline (A), after one (B) and three–month (C) treatment of alectinib

Fig. 2

Optical image of EIMS in Hematoxylin and Eosin staining with 100× (A) and 200× (B) magnification ratio in paraffin-embedded tissue. Positive expression of immunohistochemical staining for ALKp80 (diffuse, C), CD30 (D), CD10 (E), CKpan (F), EMA (focal, G), and Ki-67 (H)

Fig. 3

Negative expression of immunohistochemical staining for Desmin (A), SMA (B), SALL4 (C), MyoD1 (D), CD20 (E), and CD34 (F)