LETTER TO THE EDITOR Myoid Harmatoma of the Breast: Clinicopathologic Analysis of a Rare Tumor Indicating Occasional Recurrence Potential To the Editor: Myoid hamartoma (MH) is an extremely rare subtype of breast hamartoma characterized by the presence of myoid cell bundles in the stroma. Only approximately 30 cases have been reported to date. So its biological behavior, clinicopathologic features and histological origin are not well characterized. Moreover, its potential recurrence is usually overlooked. To the best of our knowledge, no case of MH with local recurrence has been reported previously. Herein, we described clinicopathologic features of five MHs, containing two recurrent lesions. Our aim is to elucidate pathologic features of MH, and to lay stress on its recurrence potential to evoke attentions of pathologists and surgeons. Five cases of MH were collected in the Department of Pathology, Shanghai Cancer Center, Fudan University, Shanghai. For each case, sections of 5 lm were cut from paraffin blocks for HE and immunohistochemistry using Envision method. The primary antibodies included vimentin, desmin, h-caldesmon, calponin, SMA, MSA. One case was studied ultrastructurally. The age of five patients ranged from 29 to 44 years (mean, 39 years). Physical examinations all revealed nontender, palpable lumps. The radiological information of two patients was available. On Mammography, two lesions appeared as ovoid to rounded, well circumscribed masses of mixed heterogenous density. A thin smooth capsule with peripheral radiolucent zone was seen in one lesion. In MRI, the lesion displayed an ovoid, well-defined mass with heterogenous enhancement, a focal dark thin rim. Internal fat Address for correspondence and reprint requests to: Wentao Yang, MD, PhD, Department of Pathology, Shanghai Cancer Center, Fudan University, 270 Dong’an Road, Shanghai 200032, China, or e-mail: ywentao2000@ yahoo.com. DOI: 10.1111/j.1524-4741.2011.01085.x ª 2011 Wiley Periodicals, Inc., 1075-122X/11 The Breast Journal, Volume 17 Number 3, 2011 322–324 intensity was demonstrated. All patients underwent lumpectomy. Three patients were well after the initial surgery. However, two cases developed local recurrence. One case relapsed 10 months following the initial surgery. Another recurred twice, with an interval of 36 and 41 months, respectively. Moreover, when recurred for the second time there were two separate lesions. The two original tumors were ill-defined. All patients were fine at present. The lesion size ranged from 1.4 to 2.0 cm (mean, 1.7 cm). Gross examination all revealed round, ovoid, soft or firm, nodular masses. Microscopically, three lesions were sharply demarcated, with an intact, thin, fibrous envelope. Two cases were ill-defined (Fig. 1). Each lesion was composed of breast lobules and ducts, myoid cell bundles, fibrous stroma, and mature adipose in various proportions. In one case, myoid component mingled more diffusely with adipose and fibrous tissue, exhibiting solid sheet appearance. In the remaining four cases, myoid element was scattered within the fibro-fatty background. Myoid cells, arranged in bundles or fascicles, showed the morphological appearance resembling smooth muscle cells or myofibroblasts. In two cases, myoid cells apparently arised from the myoepithelial layer of glands and merging with it. In all lesions, adipose tissues were noted in variable amounts, ranging from 5% to 20% in area. Associated epithelial changes included apocrine metaplasia, and usual or papillary hyperplasia of ductal epithelium. Neither epithelial cells nor stromal cells had prominent atypia. Mitotic figures were absent in four cases. Whereas, a few mitotic figures (1 ⁄ 10HPF) were found in myoid stroma of one recurrent tumor (Fig. 2). The immunohistochemical investigations revealed that myoid component was diffusely and strongly positive for vimentin, SMA and MSA in all tumors. All cases showed variable expression of desmin. Three cases were immunoreactive to h-caldesmon (Fig. 3) and calponin, respectively. Ultrastructural study of one case showed that there were large amounts of letter to the editor • 323 Figure 1. The lesion was ill-defined, and mingled with the surrounding normal tissue in some area (HE stain). Figure 3. Myoid stroma was positive for h-caldesmon (immunoperoxidase stain). Figure 2. A few mitotic figures were found in myoid stroma (HE stain). Figure 4. Ultrastructural features. Myoid cells showed myofibroblastic differentiation, including cytoplasmic actin filaments with fusiform dense bodies, prominent subplasmalemmal densities and a continuous basal lamina. No desmosomes or cytokeratin filaments were seen. cytoplasmic actin filaments with fusiform dense bodies and abundant organelles. Prominent subplasmalemmal densities and an almost continuous basal lamina were also seen (Fig. 4). No desmosomes or cytokeratin filaments were indentified. These features were suggestive of myofibroblastic differentiation. The histogenesis of myoid component in MH is uncertain. Different studies have raised that myoid cells originate from myoepithelium, stromal myofibroblasts, walls of blood vessel, and stromal stem cell (1), respectively. In this series, three lesions showed immunohistochemical traits of virtual smooth muscle tumors. However, one case ultrastructurally exhibited myofibrobalstic differentiation. So we propose that myoid stroma expresses smooth muscle markers immunohistochemically, while some tumors might show myofibroblastic differentiation ultrastructurally. The disparity of immunophenotype and ultrastructure of myoid cell makes it difficult to judge its differentiation direction. More studies are needed to ascertain the origin of myoid component. Although breast hamartoma is benign, rare cases with local recurrence have already been reported. Daya et al. (2) noted that two of 25 cases recurred after local excision, because the first resection was incomplete. In the series of Tse et al. (3), one lesion also developed recurrence. An incomplete excision 324 • letter to the editor may be one contributing factor of tumor recurrence. Some author (4) deems that there is no tendency local recurrence or multifocality in MH. Nevertheless, in this series, two cases developed local recurrence; one initial tumor exhibited ill-defined with a few mitotic figures. On these grounds, we presume these histological features might be suggestive of potential recurrence of MH. Unsatisfactorily, it was difficult to judge the status of surgical margins from the submitted tissue sections, so we could not rule out the possibility of incomplete resection leading to tumor recurrence. Herein, we suggest that pathologists who see illdemarcated border and mitotic figures in myoid component should be alerted to recurrence possibility in MH. Furthermore, it is essential to illustrate these morphological findings in pathological reports, in order to evoke attention of clinicians. Although the recurrence possibility of hamartoma was mentioned in literatures, surgeons have not paid enough attentions to the issue in practice. Nowadays, ‘‘Shelling out the tumor’’ is still widely applied as the routine treatment protocol. Some author (4) suggests excisional biopsy performed by ‘‘shelling out’’ the tumor is an adequate treatment for MH. However, our study has demonstrated MH does have occasional recurrence potential, so wide local excision and clear margins should be warranted. Lin Yu, MD,* Wentao Yang, MD, PhD,* Xiaoli Xu, MD, PhD,* Yajia Gu, MD, PhD, Chaofu Wang, MD, PhD,* Hongfen Lu, MD,* Weiqi Sheng, MD, PhD,* and Daren Shi, MD, PhD,* *Department of Pathology, Fudan University Shanghai Cancer Center, Fudan University, Shanghai, China Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China; and àDepartment of Diagnostic Radiography, Fudan University Shanghai Cancer Center, Shanghai Medical College, Fudan University, Shanghai, China REFERENCES 1. Tommaso LD, Pasquinelli G, Damiani S. Smooth muscle cell differentiation in mammary stromo-epithelial lesions with evidence of a dual origin: stromal myofibroblasts and myoepithelial cells. Histopathology 2003;42:448–56. 2. Daya D, Trus T, D’Souza TJ, et al. Hamartoma of the breast, an underrecognized breast lesion. Am J Clin Pathol 1995;103: 685–9. 3. Tse GMK, Ma TKF, Chan ABW, et al. Hamartoma of the breast: a clinicopathological review. J Clin Pathol 2002;55:951–4. 4. Rosen PP, (ed). 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