Myoid (Muscular) Hamartoma of the Breast: Case Report and Review of the Literature

Abstract

Background: Myoid (muscular) hamartoma (MH) of the breast is a rare benign tumour-forming lesion composed of differentiated mammary glandular and stromal structures, fatty tissue, and areas of smooth muscle. It is considered to be a variant of mammary hamartoma. Case Report: We report the case of a 46-year-old woman with MH, and provide a literature review explaining the origin of smooth muscle cells. Histologically, the tumour consisted of fibrolipomatous stroma containing ductal and lobular structures of the mammary gland located mainly at the tumour borders. The glandular structures showed signs of micro- and macrocystic changes, apocrine metaplasia, and adenosis. The dominant feature was the presence of a fascicular formation of spindle cells, predominantly in central parts, with incursion between glandular structures. Immunohistochemically, foci of smooth muscle tissue were positive for desmin, smooth muscle actin, and h-caldesmon. Oestrogen and progesterone receptors (PR) showed positive expression which was markedly higher for PR. There was negative expression of CD34, S-100 protein, and CD10. Conclusions: The origin of smooth muscle cells in MH is unknown. However, it is presumed to be derived from hormonally responsive breast stromal cells by smooth muscle metaplasia, based on evidence of hormone receptor expression in the lesion.

Bilateral myoid hamartoma of breast: An exceptionally rare lesion

“…This is supported by the expression of CD-34 in smooth muscle cells in myoid hamartoma [7]. The origin of smooth muscle cells in myoid hamartoma could be from smooth muscle cells of nipple, breast stroma or myoepithelial cells [8][9][10]. While others favour a dual origin of MH from myoepithelial cells as well as myofibroblastic components in variable proportion [9,11].…”

Breast hamartoma: A report of 14 cases of an under-recognized and under-reported entity

“…Another hypothesis concerning the origin of smooth muscle is by metaplasia of the breast stromal cells. Presence of CD34 is believed to be a crucial indicator of metaplasia of breast stromal cells into smooth muscle [12] . Other immunohistochemical markers commonly sought out in breast hamartomas, specifically myoid hamartomas, include desmin, vimentin, and SMA.…”

Myoid hamartoma of the breast that proved difficult to diagnose: a case report

“…However, diagnosing a rare disease such as myoid hamartoma using the limited tissue yield of core needle biopsy is difficult [3,11,17]. In addition, the findings on mammography, ultrasonography, and dynamic MRI were different from the histological findings of core needle biopsy.…”