Acral FibroChondroMyxoid tumor: imaging features of a new entity
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CASE REPORT
Acral FibroChondroMyxoid tumor: imaging features of a new entity Thomas Le Corroller 1,2 & Nicolas Macagno 3 & Hugo Nihous 3 & Pierre Champsaur 1,2 & Corinne Bouvier 3 Received: 9 July 2020 / Revised: 13 August 2020 / Accepted: 16 August 2020 # ISS 2020
Abstract “Acral FibroChondroMyxoid tumor” (AFCMT) is a recently described distinctive subtype of acral soft tissue tumor that typically arises on the fingers and toes. We herein present the unreported imaging features of AFCMT in a 44-year-old woman. This otherwise healthy patient was referred for a painful, slow-growing, soft tissue mass in the middle finger of her right hand. Initial radiographs and computed tomography showed a small lesion centered in the soft tissue of the ulnar aspect of the proximal phalanx, associated with scalloping of the underlying bone. Magnetic resonance imaging confirmed the presence of a wellcircumscribed soft tissue tumor that exhibited relatively high T2-weighted signal intensity and marked enhancement after contrast administration. Subsequent excisional biopsy was performed. Histologically, the tumor was characterized by an abundant stroma displaying fibrous, chondroid, and myxoid areas. By immunohistochemistry, tumor cells stained for CD34, ERG, and focally S100 protein. RNA-sequencing allowed detection of THBS1-ADGFR5 gene fusion which confirmed the diagnosis of AFCMT. At 2-year follow-up, the patient remains free of recurrence. AFCMT is a previously unrecognized entity that may mimic chondroma and should be considered in the differential diagnosis of soft tissue tumors with cartilaginous or myxoid stroma in the extremities. Keywords Extremity . Tumor . Soft tissue
Introduction “Acral FibroChondroMyxoid tumor” (AFCMT) is a recently described soft tissue tumor that occurs electively in the hands and feet and may involve the underlying bone in half of cases [1]. Histologically, this tumor presents a multinodular growth pattern composed of a proliferation of small monotonous ovoid to spindle cells. AFCMT is characterized by an abundant fibrous or chondromyxoid stroma which may account for the previous misclassification of this entity as chondroma. Immunohistochemistry is of limited help with tumor cells usually expressing CD34, ERG, SOX 9, and S100, hinting at a partial cartilaginous differentiation [1, 2]. Yet, RNA-
* Thomas Le Corroller [email protected] 1
Radiology Department, APHM, Marseille, France
2
CNRS, ISM UMR 7287, Aix Marseille University, Marseille, France
3
INSERM, MMG, APHM, CHU Timone, Department of Pathology, Aix Marseille University, Marseille, France
sequencing recently led to the identification of a recurrent THBS1-ADGFR5 gene fusion in all cases of AFCMT allowing better delineation of this entity [1]. Thus far, the imaging features of this tumor have not been described. Here, we describe the imaging appearances, including radiography, computed tomography (CT) and magnetic resonance (MR) imaging, and histological features of AFCMT arising from the soft tissue of the proximal phalanx
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