title: Characterization of the leiomyomatous variant of myofibroblastoma: a rare subset distinct from other smooth muscle tumors of the breast.
abstract: Mammary myofibroblastoma is a benign spindle cell tumor that can show variable morphologic patterns and lines of differentiation. Myofibroblastoma belongs to a family of CD34-positive tumors with similar morphology that show a deletion of 13q14, which includes RB1 and FOXO1A genes. A subset of these tumors demonstrates distinct smooth muscle differentiation. We aimed to characterize 4 cases of the leiomyomatous variant of myofibroblastoma arising in the breast by clinicopathological, immunohistochemical, and molecular means. All 4 examples arose in women aged 41 to 62 years (median, 46.5 years). Tumors ranged in size from 1.7 to 2.5 cm (median, 2.2 cm). Morphologically, all tumors were characterized by bundles of smooth muscle cells with elongated cigar-shaped nuclei and eosinophilic cytoplasm. All 4 tumors showed diffuse positive staining with desmin, caldesmon, smooth muscle actin, estrogen receptor, and Bcl-2. CD34 staining was diffusely positive in 2 cases, was weak and patchy in 1 case, and was negative in 1 case. Two (50%) of 4 tumors showed deletion of RB1 by fluorescence in situ hybridization. Loss of Rb staining was seen in 1 tumor with RB1 deletion by fluorescence in situ hybridization, whereas intact Rb staining was observed in 1 nondeleted case studied. In conclusion, this rare variant of myofibroblastoma is a distinct subgroup of tumors among an already uncommon category of (smooth muscle) breast tumors. Some reported examples of "parenchymal leiomyoma" may represent the leiomyomatous variant of myofibroblastoma.
authors: Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10065. Electronic address: tid9007@med.cornell.edu.
authors: Timothy M
authors: TM
authors: D'Alfonso
authors: Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10065.
authors: Shivakumar
authors: S
authors: Subramaniyam
authors: Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10065.
authors: Paula S
authors: PS
authors: Ginter
authors: Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10065; Institute for Precision Medicine of Weill Cornell and New York-Presbyterian Hospital, New York, NY 10065.
authors: Juan Miguel
authors: JM
authors: Mosquera
authors: Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10065.
authors: Theresa Y
authors: TY
authors: MacDonald
authors: Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10065.
authors: Zohal
authors: Z
authors: Noorzad
authors: San Pablo Pathology Group, Bayamon, Puerto Rico 00959.
authors: Lurmag Y
authors: LY
authors: Orta
authors: Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10065.
authors: Yi-Fang
authors: YF
authors: Liu
authors: Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10065; Institute for Precision Medicine of Weill Cornell and New York-Presbyterian Hospital, New York, NY 10065.
authors: Mark A
authors: MA
authors: Rubin
authors: Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10065.
authors: Sandra J
authors: SJ
authors: Shin
mesh_terms: D000328:Adult; D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics; D001943:Breast Neoplasms / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000473:pathology*; D005260:Female; D017353:Gene Deletion; D020022:Genetic Predisposition to Disease; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D007889:Leiomyoma / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000473:pathology*; D008875:Middle Aged; D009379:Neoplasms, Muscle Tissue / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000473:pathology*; D010641:Phenotype; D056286:Retinoblastoma Binding Proteins / Q000032:analysis / Q000235:genetics; D044767:Ubiquitin-Protein Ligases / Q000032:analysis / Q000235:genetics
chemical_list: D014408:Biomarkers, Tumor; C000606393:RB1 protein, human; D056286:Retinoblastoma Binding Proteins; D044767:Ubiquitin-Protein Ligases
keywords: 13q14; CD34; Leiomyomatous; Myofibroblastoma; RB1