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 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 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.