ALK-1 protein expression and ALK gene rearrangements aid in the diagnosis of inflammatory myofibroblastic tumors of the female genital tract

Abstract

Context: Inflammatory myofibroblastic tumor is a predominantly benign, spindle cell, mesenchymal neoplasm with myxoid areas that occurs rarely in the female genital tract and may be confused with other spindle cell lesions, particularly leiomyosarcoma.

Objective: To investigate the utility of detecting anaplastic lymphoma kinase-1 protein expression and ALK gene rearrangements in the diagnosis of inflammatory myofibroblastic tumors in the female genital tract.

Design: Eight inflammatory myofibroblastic tumors arising in the female genital tract and seen in consultation (from 2004 to 2011) were reviewed. Immunohistochemistry for anaplastic lymphoma kinase-1 and fluorescence in-situ hybridization studies for ALK gene rearrangements were performed.

Results: The anatomic sites included myometrium (4 cases) and endometrium, fallopian tube, cervix, and a cervical polyp (1 each), with a patient age range from 25 to 52 years. Histologic features ranged from bland spindle cells to striking cytologic atypia, embedded in a prominent myxoid background. Anaplastic lymphoma kinase-1 immunohistochemistry was positive in 7 cases. Fluorescence in-situ hybridization studies detected ALK gene rearrangements in 5 cases. Five cases had both immunopositivity and fluorescence in-situ hybridization abnormalities, 2 cases had immunopositivity only, and 1 case was negative by both methods.

Conclusions: This is the first report, to our knowledge, of ALK gene rearrangements in inflammatory myofibroblastic tumors in the female genital tract. If a myxoid background is appreciated in a spindle cell lesion of the female genital tract, especially if inflammatory cells are present, anaplastic lymphoma kinase-1 staining along with fluorescence in situ hybridization studies, for ALK gene rearrangements, may aid in distinguishing inflammatory myofibroblastic tumors from their malignant mimics.