ORIGINAL ARTICLE Mammary Pseudoangiomatous Stromal Hyperplasia Composed of Predominantly Giant Cells: An Unusual Variant Nil C ¸ omunog ˘lu, MD,* Cem C ¸ omunog ˘lu, MD, † S ¸ ennur _ Ilvan, MD, ‡ Zerrin Calay, MD, ‡ and Mahmut Mu ¨ slu ¨ manog ˘lu, MD § *Department of Pathology, Yeditepe University Medical Faculty, Kayıs ¸ dag ˘ ı, _ Istanbul, Turkey; † Department of Pathology, Turkish Cancer Institute, S ¸ is ¸ hane, _ Istanbul, Turkey; ‡ Department of Pathology, _ Istanbul University, Cerrahpas ¸ a Medical Faculty, Cerrahpas ¸ a, _ Istanbul, Turkey; and § Department of Surgery, _ Istanbul University, C ¸ apa Medical Faculty, C ¸ apa, _ Istanbul, Turkey n Abstract: Pseudoangiomatous stromal hyperplasia (PASH) is a benign proliferative lesion of mammarian stroma that presents as a localized mass. We describe the clinical, radiologic, cytologic, and histopathologic features of a case of PASH with giant cells that presented as a rapidly growing localized mass in the breast in a 32-year-old woman. An unusual feature of our case was the presence of multinucleated giant cells lining pseudovascular spaces and dispersing in collagenous stroma. To the best of our knowledge, this is the second case in the English literature and PASH with predominance of mul- tinucleated giant cells has never been described previously in a female patient. n Key Words: breast, giant cells, pseudoangiomatous stromal hyperplasia P seudoangiomatous hyperplasia (PASH) of the mammarian stroma was first described by Vuitch et al. in 1986 (1). It presents as a localized mass in premenapausal woman and simulates low grade an- giosarcoma and fibroadenoma. PASH of the breast is recognized either as an incidental microscopic finding or a clinically palpable lesion (2). The etiology of PASH remains unknown, but most authors believe that PASH represents a neoplastic process of myofib- roblastic origin. PASH is a tumor formed by myofi- broblasts with variable expression of myxoid and fibroblastic features (3,4). In this article, we describe a case of PASH with unusual giant cell features. CASE HISTORY A 32-year-old woman presented with a 3 month history of a rapidly growing mass in her left breast. Medical history revealed insignificant findings. Physical examination showed a nonfixed, nontender, well-defined mass with rubbery consistence in the upper quadrant of her left breast. The nipple and are- ola were unremarkable. No axillary lymph nodes were palpable. A bilateral mammogram revealed a 27.9 · 22.5 · 15.1 mm circumscribed mass in her left breast. Sonographic examination of both axillary regions revealed no lympadenopathy. Gross examination showed a 2.5 · 2 · 1.5 cm, well-circumscribed, breast mass with rubbery consis- tence. Cut-surface was yellow-pinkish, homogenous, and bright. Hemorrhage and necrosis were not detected. Frozen section samples of the breast mass were evaluated and interpreted as stromal hyperplasia with giant cells. Materials and Methods Tissue from the excisional biopsy was fixed in 10% neutral-buffered formalin. Representative samples were embedded in paraffin. Five micron sections were obtained and stained with hematoxylin and eosin. Immunohistochemical studies were performed on formalin fixed paraffin-embedded sections using the standard avidin–biotin peroxidase complex technique and the peroxidase-anti peroxidase technique. (CD34, OB-END ⁄ 10, monoclonal, 1:400, Neomarkers; Lab Address correspondence and reprint requests to: Dr. Nil C ¸ omunog ˘lu, MD, Department of Pathology, Yeditepe University School of Medicine, 26 Ag ˘ ustos Campus, Kayıs ¸ dag ˘ ı 34755, Istanbul, Turkey, or e-mail: nilustundag@yahoo.com and ncomunoglu@yeditepe.edu.tr. ª 2007 Blackwell Publishing, Inc., 1075-122X/07 The Breast Journal, Volume 13 Number 6, 2007 568–570