Track: Case Reports

Topic: Neoplasia,Carcinogensis,Tumor Biology

Abstract:

First described in 2018, EWSR1-SMAD3 rearranged fibroblastic tumor (ESRFT) is a soft tissue tumor with fewer than 20 cases described in the literature. The tumor has an apparent female predominance and occurs most commonly on acral locations. We present a case of ESRFT highlighting the utility of ERG staining for diagnosis.

A 47-year-old woman presented to dermatology with a 0.5 cm pearly nodule on the left lateral heel. The lesion had been present unchanged for several years. It was intermittently painful, especially when ambulating. A shave biopsy was done with a differential diagnosis of glomus tumor, angioma, and benign nerve sheath tumor.

Histology demonstrated a cellular spindle cell neoplasm within the dermis. The cells had uniform, bland nuclei without appreciable atypia or mitotic activity. The spindle cells formed intersecting fascicles within a scant collagenous stroma. Diagnostic considerations included dermatofibroma, hybrid peripheral nerve sheath tumor, and spindle cell hemangioma. Immunohistochemical stains were performed and, notably, the spindle cells showed strong diffuse immunoreactivity to ERG but were negative for CD34. No specific staining of the spindle cells was seen with S-100 protein, SOX-10, Factor XIIIa, EMA, or MART-1. The clinical presentation, morphology, and ERG positivity raised the possibility of ESRFT. EWSR1 gene rearrangement testing by FISH break apart probe was positive supporting the diagnosis.

The recommended treatment for ESRFT is complete excision of the lesion as early evidence suggests a risk for recurrence. We present this case to raise awareness of this newly described entity.

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Eleni Pilitsi, MD