Fibroblastic and Myofibroblastic Tumors in Children and Adolescents

Abstract

Fibroblastic and myofibroblastic tumors in children and adolescents are a relatively common group of soft tissue proliferations that range from reactive to hamartomatous to neoplastic, with a full spectrum of benign, intermediate, and malignant neoplasms. These lesions are diagnostically challenging because of morphologic and immunohistochemical overlap, despite significant clinical, genetic, and prognostic differences. The fibromatoses are a major subgroup, and all types of fibromatoses can occur in the 1st 2 decades of life. Intermediate and malignant fibroblastic-myofibroblastic tumors are an important group that includes variants of fibrosarcoma and other tumors with recurrent cytogenetic or molecular genetic abnormalities and low metastatic potential. Pathologic examination is enhanced by adjunct techniques, such as immunohistochemistry, cytogenetics, and molecular genetics, although morphology provides the ultimate criteria for a specific diagnosis. This article reviews the clinicopathologic features of fibroblastic and myofibroblastic tumors with an emphasis on the unique aspects of these neoplasms in children and adolescents, the use of diagnostic adjuncts, and differential diagnoses.

Infantile Digital Fibroma: A Rare Fibromatosis

“…However, these inclusions vary in number, and in rare cases may be absent. 5,12 Tumors with decreased numbers of inclusion bodies often show an increase in fibrosis, and this process is thought to be related to the age of the lesion with younger lesions having more inclusions accompanied by less fibrosis and older lesions having less inclusions with more fibrosis. 19 …”

“…It often causes a dome-shaped elevation of the overlying structures, forming a protuberant or polypoid nodule ( Figure 3). 5,12,18 Tumor cells have pale eosinophilic cytoplasm with plump, elongated nuclei, a thin membrane, and finely granulated chromatin. In the superficial dermis there are ectatic thin-walled vessels that become slitlike in the deep dermis.…”

“…20 Actin-related immunohistochemical stains have shown variable staining for the inclusions (Figure 6). 5,12,21 The spindle cells of the lesion typically show cytoplasmic staining for calponin, a-smooth muscle actin, and desmin, and membranous staining for CD99. 5,12,21 ELECTRON MICROSCOPY The ultrastructure of the spindle cells shows the presence of discrete bundles of microfilaments that contain many dense bodies that measure between 5 and 7 nm in diameter as well as filaments that are not bundled that measure 10 nm in diameter.…”

“…5,12 The overlying epidermis can display a host of changes, including acanthosis, hyperkeratosis, parakeratosis, rete ridge flattening, entrapment of adnexal structures, and, rarely, ulceration. The lesion itself is made up of a proliferation of bland intradermal spindle cells arranged in whorls, fascicles, or a storiform pattern in a collagenous background of varying degrees ( Figure 2).…”

“…9,10 Still, the etiology and pathogenesis of infantile digital fibroma remain unclear, with no large series demonstrating an association between infantile digital fibroma and genetic disorders or malformations. 11,12 CLINICAL FEATURES In the largest study, which included 57 patients, Laskin et al 5 found that the mean age at presentation was 22 months with ages ranging from newborn to 10 years. However, the tumor has been reported to appear much later in life as well.…”