Anaplastic Lymphoma Kinase (ALK)-Negative Inflammatory Myofibroblastic Tumor of the Kidney in a Nine-Month-Old Girl

Abstract

An inflammatory myofibroblastic tumor (IMT) is an uncommon, benign tumor of myofibroblastic spindle cells. An IMT can occur in any part of the body. However, involving kidney is exceedingly rare. When this rare entity occurs in children, it becomes incredibly challenging to distinguish this rare entity from other malignancies such as Wilms tumor. Although imaging studies of the abdomen and pelvis add to the diagnosis, however, histological examination and immunohistochemical staining remain the gold standard for the precise diagnosis of this rare entity. To the best of our knowledge, only 48 cases of renal IMT have been published in the medical literature so far. We report the case of a nine-month-old girl who was brought with complaints of hematuria, and later, imaging and histological confirmation revealed an anaplastic lymphoma kinase (ALK)-negative IMT of the kidney.

Keywords: benign; ct (computed tomography) imaging; hematuria; inflammatory myofibroblastic tumor; wilms tumor.

Figure 1. MRI revealing well-defined, predominantly solid hypoenhancing right renal mass with a small cystic area in the periphery of the lesion

Figure 2. Gross examination: well-circumscribed lesion with focal hemorrhage

Figure 3. Histological examination: hematoxylin and eosin stain (H&E)

A, B, H&E and bland spindle cells with mixed inflammatory infiltrate. C, Spindle cells showed nuclear and cytoplasmic positivity for cyclin D1. D, Spindle cells are negative for ALK stain. ALK: anaplastic lymphoma kinase.