Myoid Hamartoma of the Breast: A Case Report

Chromosomal Translocation t(5;12)(p13;q14) Leading to Fusion of High-mobility Group AT-hook 2 Gene With Intergenic Sequences From Chromosome Sub-Band 5p13.2 in Benign Myoid Neoplasms of the Breast: A Second Case

“…The immunohistochemical profile of myoid hamartoma is similar to that of leiomyoma. They stain positively for specific markers of smooth-muscle differentiation such as smooth muscle actin, vimentin, desmin, and caldesmon (15,18,22,24,25), and they are also positive for estrogen and progesterone receptors (15,18,22,24,25). A similar positivity for estrogen receptors and progesterone receptors has also been found in retroperitonealabdominal cavity leiomyomas (44,45), uterine leiomyomas (46)(47)(48)(49), and most breast hamartomas (50,51).…”

“…The general histological description of myoid hamartomas of the breast maintains that in this tumor, the smooth muscle component is mixed with other elements such as adipose tissue, fibrous stroma, and glandular tissues (22,25).…”

“…The smooth muscle component of myoid hamartomas is intriguing because, apart from the erector muscle of the nipple and the vessels, smooth muscle cells are generally absent from normal mammary stroma (13,21). Thus, in myoid hamartomas, the smooth muscle tumor component was suggested to originate from the myoepithelium through a metaplastic process, or from stromal myofibroblasts, from the walls of local vessels, or from a stem cell capable of multidirectional differentiation (5,6,8,11,13,18,21,25,52). In the third and fourth editions of Rosen's Breast Pathology textbook, the authors treat hamartoma and myoid hamartoma as two different lesions, writing about the latter that "Regrettably, the designation of these tumors as hamartomas is now well entrenched in the literature", signaling the opinion that myoid hamartomas may not be true hamartomas (42,53).…”

“…Judging by the publication record, myoid hamartomas of the breast are very rare benign lesions, most of which have been reported as single cases (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). The differential diagnosis of myoid hamartoma includes various tumor-like lesions showing smooth muscle differentiation and spindlecell tumors including fibroadenoma, myofibroblastoma, leiomyoma, and leiomyosarcoma (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25).…”

“…Differential diagnosis of the many phenotypically somewhat variable benign myoid lesions that can be found in the breast is not always possible nor is it necessarily clinically relevant (21,22,25). Nevertheless, a general histological description of myoid hamartoma of the breast is that the prominent smooth muscle component is mixed with other breast elements such as adipose tissue, fibrous stroma, and glandular tissue (22,25).…”