Journal of Plastic, Reconstructive & Aesthetic Surgery (2013) 67, e93ee94

CORRESPONDENCE AND COMMUNICATION Heterotopic ossification in cauliflower ear Dear Sir, The cauliflower ear is a thickened deformity of the external ear seen after repeated traumatic hematoma formation in the auricle, and most commonly caused by sporting activity, such as rugby, boxing, wrestling and judo or injury from a fall or motor vehicle accident.1 This hypertrophied tissue is commonly considered to consist of fibrosis and neocartilage, resulting from the scarring and stimulation of mesenchymal stem cells in the perichondrium caused by bleeding between the perichondrium and the cartilage or perichondritis.2 When performing otoplasty, however, we sometimes experience a bone-like hardness in the hypertrophied tissues of a cauliflower ear. We have previously reported multiple ossifications in the cauliflower ear patient using computed tomographic scan.3 Herein, we report another case of the cauliflower ear in which detailed histopathological findings showed rigid bone formation in the excised specimen. A 22-year-old male presented with a severe deformity of the right ear as a result of playing rugby for 4 years (Figure 1). The outline of the entire ear had significantly changed with protruding thick tissues, and the structural integrity was poor. Otoplasty was performed from a postauricular incision, and the ear cartilage and hypertrophied tissues were completely exposed. The deformed, hyperplastic tissues were then shaved with a scalpel to restore normal shape, and the skin was closed with application of a bolster suture to the scaphoid fossa. Surgical specimens, grossly ash gray solid and hard masses, were submitted to the pathological department for detailed examination. The wound healed well, and the ear maintained a good contour at 1-year follow-up observation. The decalcified, and azan-stained (which shows collagen fiber as deep blue, cartilage matrix as light blue, and nuclei as bright red) specimens revealed presence of fibrosis, cartilage, and bone structure (Figure 2). As only abnormal tissues were removed, all of these tissues were thought to

derive from tissue neogenesis. The neonatal bone showed almost the same structure as normal bone including trabeculae, though it lacked bone marrow. Regarding distribution, the neonatal bone constituted a large portion of the specimen, contacting primarily the fibrous tissue, and also the neocartilage, but to the lesser extent. Abundant blood vessels were also observed, as were a proliferation of fibroblasts, and a slight spreading of osteoblasts. Calcification and atypical tissue were not observed. Heterotopic ossification (HO) is defined as bone formation in non-osseous tissues, usually occurring in trauma such as fractures, surgical procedures such as arthroplasty, and

Figure 1 Preoperative appearance of the cauliflower ear. A 22-year-old male with rugby injury, resulting in a projected, solid deformity of the right ear. The dotted line shows the site where the specimen was surgically excised.

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Correspondence and communication cauliflower ear condition, which our case suggested, may provide valuable insight into efforts to clarify the osteogenic potential in the perichondrium, which could help in developing a new treatment for bone/cartilage regeneration, although further studies are needed.

Financial disclosure and products Authors report no conflict of interest or funding with regard to this manuscript.

References Figure 2 Pathological finding of the cauliflower ear (Azan stain)(100). Azan stain clearly discriminated fibrosis, cartilage, and bone structure. The neonatal bone principally contacted the fibrosis, and partially with neocartilage. These induced tissues are believed to derive from stimulated mesenchymal stem cells in the perichondrium.

neurologic disorders such as spinal cord injury.4 Although the exact cause of HO remains unknown, it is presumed that pluripotential mesenchymal cells differentiate into osteoblasts, and in turn cause endochondral ossification. Research has yet to determine the source of these mesenchymal cells or the stimulus that causes them to differentiate. In our case, mesenchymal stem cells in the perichondrium emerged as candidates for the osteogenic origin. Although no osseous system or bone-forming properties exist in an external ear, a considerable degree of HO was observed in the excised tissues, and the neonatal bone exhibited rigid structures comparable to normal bone. Recent studies have confirmed that the perichondrium has the potential for not only chondrogenesis but also osteogenesis5; it is presumed that hematoma formation detached the perichondrium from the cartilage and stimulated the perichondrial stem cells, filling the dead space with fibrogenesis, chondrogenesis, and osteogenesis. Hematoma itself may also play an important role, as fracture hematoma possesses multiple inflammatory and growth factors in endochondral ossification. Marrow elements were not observed in our case, probably because bone marrow formation is angiogenesis-dependent and requires a more prolonged course. Although cauliflower ear has been known to develop solely of fibrosis and neocartilage, our case exhibited a considerable degree of HO in surgically excised tissues of the cauliflower ear, as well as fibro-neocartilaginous material. The revision of the current concepts of the

1. O’Donnell BP, Eliezri YD. The surgical treatment of traumatic hematoma of the auricle. Dermatol Surg 1999;25:803e5. 2. Ohlse ´n L, Skoog T, Sohn SA. The pathogenesis of cauliflower ear. An experimental study in rabbits. Scand J Plast Reconstr Surg 1975;9:34e9. 3. Mashiko T, Mori H, Kato H, et al. Semipermanent volumization by an absorbable filler: onlay injection technique to the bone. Plast Reconstr Surg Glob Open 2013;1:e4. 10.1097/GOX.0b013e31828c66b0. 4. Chao ST, Suh JH, Joyce MJ. Treatment of heterotopic ossification. Orthopedics 2007;30:457e64. 5. Hojo H, Ohba S, Taniguchi K, et al. Hedgehog-Gli activators direct osteo-chondrogenic function of bone morphogenetic protein toward osteogenesis in the perichondrium. J Biol Chem 2013;288:9924e32.

Takanobu Mashiko Department of Plastic Surgery, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe, Saitama 350-8550, Japan Department of Plastic Surgery, University of Tokyo, School of Medicine, 7-3-1, Hongo, Bunkyo-Ku, Tokyo 113-8655, Japan E-mail address: [email protected] Toshiharu Minabe Ichiro Shiokawa Department of Plastic Surgery, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe, Saitama 350-8550, Japan Kazuhide Mineda Kotaro Yoshimura Department of Plastic Surgery, University of Tokyo, School of Medicine, 7-3-1, Hongo, Bunkyo-Ku, Tokyo 113-8655, Japan

18 August 2013

Heterotopic ossification in cauliflower ear.

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