title: Spindle cell lipoma-like tumor, solitary fibrous tumor and myofibroblastoma of the breast: a clinico-pathological analysis of 13 cases in favor of a unifying histogenetic concept.
abstract: We reviewed the clinico-pathological features of a series of 13 cases of benign spindle stromal tumors (BSSTs) of the breast relating to a basic common theme consisting of a well-circumscribed proliferation of vimentin+/CD34+/BCL-2+/CD99+ spindly to oval-epithelioid cells, variably arranged in haphazard to short fascicular growth pattern, with interspersed thick or thin collagen bands. Morphological variations included atypical mono- or multi-nucleated cells in five cases and a mature lipomatous tumor component, varying from focal to prominent, in eight cases. Based on morphological and immunophenotypical features, a distinction was made between two main subtypes of these tumors--fibroblastic and myofibroblastic. The former subtype included two cases respectively represented by a typical solitary fibrous tumor (SFT) and a neoplasm labeled "spindle-cell lipoma (SCL)-like tumor", closely reminiscent of soft tissue SCL. Both tumors had cells with fibroblastic-like appearance, haphazardly arranged and immunoreactive for vimentin, CD34, BCL-2, and CD99. The latter subtype, comprised nine cases exhibiting evidence of myofibroblastic differentiation (desmin and alpha-smooth muscle actin) which were classified as myofibroblastomas (MFBs). The remaining two cases were defined as "mixed BSSTs", having typical features of diverse neoplasms, respectively represented by a case of MFB with focal SFT and pleomorphic/SCL-like areas, and SFT with focal MFB-like component. The common basic morpho-immunophenotypical features, the possibility that both fibroblastic and myofibroblastic tumors may contain an additional mature lipomatous component, and the existence of hybrid stages (mixed BSSTs) strongly support the view that such tumors belong to the same category of lesions. We postulate that the precursor of all these neoplasms is the vimentin+/CD34+ cells of the mammary stroma, the well-known inherent plasticity of which to differentiate toward several mesenchymal lines, provides the explanation for the phenotypic heterogeneity of these neoplasms. Accordingly, the encompassing term "benign spindle stromal tumors of the breast" is advocated for such tumors.
authors.affiliation: Istituto di Anatomia Patologica, Università di Catania, Via Biblioteca 4, 95124 Catania, Italy. gaetano.magro@tiscalinet.it
authors.forename: Gaetano
authors.initials: G
authors.lastname: Magro
authors.forename: Michele
authors.initials: M
authors.lastname: Bisceglia
authors.forename: Michal
authors.initials: M
authors.lastname: Michal
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Eusebi
mesh_terms: D000071443:12E7 Antigen; D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD / Q000032:analysis; D018952:Antigens, CD34 / Q000032:analysis; D014408:Biomarkers, Tumor / Q000032:analysis; D018567:Breast Neoplasms, Male / Q000737:chemistry / Q000209:etiology / Q000473:pathology*; D015815:Cell Adhesion Molecules / Q000032:analysis; D005260:Female; D005350:Fibroma / Q000737:chemistry / Q000209:etiology / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D008067:Lipoma / Q000737:chemistry / Q000209:etiology / Q000473:pathology*; D008297:Male; D008327:Mammography; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000032:analysis; D009379:Neoplasms, Muscle Tissue / Q000737:chemistry / Q000209:etiology / Q000473:pathology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D017154:Stromal Cells / Q000737:chemistry / Q000473:pathology; D014746:Vimentin / Q000032:analysis
chemical_list: D000071443:12E7 Antigen; D015703:Antigens, CD; D018952:Antigens, CD34; D014408:Biomarkers, Tumor; C061828:CD99 protein, human; D015815:Cell Adhesion Molecules; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D014746:Vimentin