Low-Fat Plexiform Spindle Cell Lipoma With Prominent Myxoid Stroma

Abstract

Spindle cell lipoma (SCL) and pleomorphic lipoma constitute a spectrum of lipomatous lesions with distinctive clinicopathological features. Multiple variants of SCL have been reported including fibrous, plexiform, vascular, pseudoangiomatous, low-fat/fat-free, and myxoid changes. This paper describes an unusual patient with a 1-cm submucosal nodular lesion excised from the buccal mucosa of a 55-year-old woman with classic histopathological and immunohistochemical features of "low-fat" plexiform SCL with prominent myxoid stroma, which initially suggested a soft-tissue myxomatous lesion other than SCL. The current lesion exhibited microscopically few adipocytes supported by network-like myxoid proliferations with retraction artifacts from the surrounding stromal connective tissue. Immunohistochemistry was positive for vimentin, CD34, CD10, and S100, the latter only on adipocytes. The Ki-67 was <1%. Pan-cytokeratin (AE1/AE3), desmin, alpha-SMA, EMA, bcl-2, p53, and remarkably retinoblastoma protein (pRb) were negative. "Low-fat" plexiform SCL bear no significant prognostic significance, but this lesion may challenge the diagnosis even experienced pathologists.

Fat-Free Spindle Cell Lipoma of the Scalp: Lipoma Without a Lipogenic Component

“…Fat-free lipomas are exceedingly rare, even more so than low-fat lipomas 9 . Due to significant morphologic overlap and lack of classic adipocytic content, this subtype is often mistaken for other benign and malignant soft tissue tumors 1,2,4,8 . We present the case of a middle-aged man with a fat-free SCL of the temporal scalp, which posed a challenge for histologic interpretation.…”

“…Spindle cell lipoma (SCL) is a variant of a lipoma, the most common benign soft tissue tumor of the head and neck. it is distinguished by the histopathologic appearance of the tumor stroma and varying amounts of the mesenchymal components 3,4,7,8 . it classically occurs as a solitary, subcutaneous, well-circumscribed lesion on the upper trunk, neck, or shoulders of middle-aged men 1,2,4,6,7,8 .…”

“…it is distinguished by the histopathologic appearance of the tumor stroma and varying amounts of the mesenchymal components 3,4,7,8 . it classically occurs as a solitary, subcutaneous, well-circumscribed lesion on the upper trunk, neck, or shoulders of middle-aged men 1,2,4,6,7,8 . Despite lipomas commonly arising in the head and neck, only a select number of cases of SCL have been described in this region 7,8 .…”

“…Despite lipomas commonly arising in the head and neck, only a select number of cases of SCL have been described in this region 7,8 . Histologically, SCL is composed of an admixture of mature adipocytes, CD-34 positive bland spindle cells arranged in characteristic parallel arrays (“school of fish“), bundles of ropey collagen, myxoid matrix, blood vessels, and mast cell infiltration 1,2,4,6,8 . Multiple subtypes have been reported due to a variation among these elements that differ from the prototypical SCL.…”

“…Multiple subtypes have been reported due to a variation among these elements that differ from the prototypical SCL. Variants include fibrous, plexiform, vascular, pseudoangiomatous, myxoid, fat-rich, and low-fat/fat-free 1,4,6,8 . Billings and Folpe 1 defined the latter as having a very small number of mature adipocytes (<5%) or a lack thereof.…”