Lipomatous (Fat-Forming) Solitary Fibrous Tumor of the Breast: A Case Report of an Uncommon Variant of a Rare Clinical Entity

Abstract

Solitary fibrous tumor (SFT) is an uncommon tumor of mesenchymal origin, which can arise at any anatomic location and can exhibit versatile histological features and a clinical course ranging from benign to frankly malignant. Lipomatous (fat-forming) SFT is a morphological variant of SFT characterized by an adipose tissue component. Breast SFT is an extremely rare clinical entity, and the literature review yielded only 28 previously reported cases. However, lipomatous (fat-forming) SFT is much less common than conventional tumors and, to our knowledge, it has never been reported in the breast. We describe a case of a 54-year-old postmenopausal woman who presented with a palpable mass on her right breast. No other associated features such as nipple discharge, skin changes, or axillary lymphadenopathy were present. The clinical differential diagnosis included fibroadenoma, phyllodes tumor, and mammary hamartoma. A ultrasound scan examination demonstrated a large, oval, well-circumscribed lesion with indeterminate features, but suspicious of malignancy. However, a needle core biopsy was performed and histological examination with ancillary immunohistochemical staining confirmed the diagnosis of SFT, a lipomatous variant. The lesion was excised with clear margins and histological examination confirmed SFT with low-risk features and follow-up was planned. Careful histological evaluation with diffuse and strong nuclear expression of STAT6 helped to distinguish lipomatous SFTs from other mimics. Here, we describe the first case of a lipomatous variant of a SFT involving the breast.

Incidental finding of solitary fibrous tumor of male breast: case report and review of literature

“…They have a great similarity with other soft tissue neoplasms, hence its name “great simulator” which makes their diagnosis difficult and confusing with other differential diagnoses [ 6 ]. Although it can be found everywhere, the most common site of initial presentation is the thorax; nevertheless, breast involvement remains rare, and even less often, in men’s breasts [ 6 , 7 ]. To date, very few cases have been reported.…”

“…There were no risk factors associated with the development of these tumors [ 1 ]. SFTs are usually discovered incidentally or through non-specific symptoms [ 2 ], but they rarely present with hypoglycemia linked to a paraneoplastic syndrome, also known as Doege–Potter syndrome [ 1 , 7 ]. Unlike the other cases, for SFT in male breasts, a painless breast mass or tender breast mass was the main symptom at presentation in all reported cases.…”

“…A combination of IHC staining markers is used to identify SFT, including CD34, Bcl-2, and particularly STAT6, which is a highly sensitive (98–100%) and specific (100%) nuclear marker for SFT at all anatomical locations, regardless of tumor morphology. The identification of nerve growth factor-inducible (NGFI)-A binding protein 2 (NAB2)–STAT6 or nuclear factor I/X (NFIX)–STAT6 fusion oncogenes was developed as a specific cytogenetic marker for SFT [ 1 , 7 , 14 ]. The overexpression of glutamate ionotropic receptor α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) type subunit 2 (GRIA2) has also been reported [ 1 ].…”

“…SFTs are mostly benign, but many pathological parameters have been identified and are associated with a poor prognosis; therefore, some SFTs can reappear, metastasize, and lead to death [2,7]. The World Health Organization Classification of Tumors of Soft tissue and Bone divides them into two categories: benign and malignant [7,15].…”

Solitary fibrous tumor of male breast: A case report and literature review

“…In histology, SFT shows a typical pattern-less growth of the spindle cells, alternating with hypercellular and hypocellular areas, and needs to be distinguished from other spindle cell lesions, such as myofibroblastoma, fibroblastic spindle cell tumor, spindle cell lipoma, fibroma and pseudoangiomatous stromal proliferation. When breast SFT exhibited dedifferentiation or lipomatous change in morphological variant cases, [ 10 , 11 ] malignant phyllodes tumor and liposarcoma should also be included in the differential diagnosis. In IHC analysis, a combination of CD34, Bcl-2, and CD99 positivity was traditionally used for the diagnosis of breast SFT; however, it was insufficient for the definitive diagnosis because approximately 10% of breast SFT was negative for CD34, while Bcl-2 and CD99 are more sensitive but less specific.…”