“Low-Fat” Pseudoangiomatous Spindle Cell Lipoma

Abstract

Abstract:Spindle cell and pleomorphic lipoma constitute a spectrum of lipomatous lesions with characteristic clinical, morphologic, immunohistochemical, and molecular features. Multiple variants have been previously described including vascular, fibrous, plexiform, and those with significantly less fat termed “low-fat” and “fat-free” by Folpe. Cytogenetically, spindle cell lipomas frequently display monoallelic loss of 13q14 region, an abnormality also found in cellular angiofibroma and mammary-type myofibroblastoma. Pseudoangiomatous spindle cell lipoma, originally described by Fletcher et al in 1994, is a rare variant within the spindle cell/pleomorphic lipoma spectrum, with less than 20 published cases. It consists of an admixture of spindle cells, “ropey” collagen, variable amounts of mature fat, and irregular, branching slit-like vascular spaces. The authors present a case of a 1-cm subcutaneous lesion excised from the neck of a 70-year-old man with classic histologic and immunohistochemical features of “low-fat” pseudoangiomatous spindle cell lipoma. Fluorescence in situ hybridization demonstrated a loss of 13q14 region, a characteristic presumed cytogenetic finding of spindle cell lipoma, which has been previously unconfirmed in this variant.

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

“…Spindle cell lipomas are painless, slow growing, subcutaneous tumors that typically occur on the trunk, shoulders and neck of middle-aged men, specifically in the mid 50's 1,2,3,4,6,7,8 . A review article by Chen et al 3 reported 7 cases occurring in the head region, of which 2 were on the forehead and 2 in the occipital region of the scalp, neither of which were low-fat/free-fat variants.…”

“…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.…”

Comprehensive Review of Reported Nonclassical Spindle Cell Lipoma Presentations and a Unique Case Report

“…These slow-growing benign soft tissue tumors typically present in the subcutaneous layer of the back, shoulder, or neck of White men between the ages of 40–70. 2,4 Pathological differentiation from liposarcoma, malignant lesions, myxoid tumors, and other spindle cells is important. When pathology determines an SCL, prognosis is consistently good; thus, definitive treatment is considered to be wide local excision.…”