Extrapleural Solitary Fibrous Tumor of Foot: A Case Report

Abstract

A 77-year-old woman was admitted to our Hospital for a mass lesion in the plantar area of the
left foot. The patient referred that the mass was present for about 30 years but it had never been
treated before because asymptomatic. Foot Magnetic Resonance Imaging (MRI) reviewed a
low-signal-intensity tumor on both T1 weighted and T2 weighted images. Based on clinical
and diagnostic imaging findings we initially suspected a fibroproliferative neoplasm like an
aggressive fibromatosis. Histologically the lesion was benign fibroblastic spindle cell lesion
with dense or loose collagen fibers. Cellularity was low and no mitotic figures were found. The
tumor cells were positive for CD34, whereas they were negative for α smooth muscle actin,
desmin, HHF35 and S100 protein. These pathological findings were consistent with an Extrapleural
Solitary Fibrous Tumor (Extrapleural SFT). The Extrapleural SFT should be included
in the differential diagnosis of extrapleural lesions in which MRI suggests fibrous content.
These entities exhibit a dense fibrocollagenous matrix that can produce low signal intensity on
T2-weighted MRI images, similar to Extrapleural SFT. However, in order to reach a proper diagnosis
and treatment is essential to integrate a detailed patients’ clinical history and to perform
a biopsy to collect cells for closer examination.