Abstract

Breast tumours showing pure myoepithelial or epithelial myoepithelial differentiation are rare. Adenomyoepithelioma (AME) is defined as proliferation of both epithelial and myoepithelial elements. It is characterized by biphasic morphologic population, epithelial and myoepithelial with predominantly solid, clear cell myoepithelial proliferation and luminal epithelial element. When the glandular elements predominate with glands lined by two row of cells, it is termed as Adenomyoepithelial adenosis (AA) where inner luminal layer of apocrine cells and outer row of clear cells is present. This adenosis is known to be either preceding to AME or is an integral part of it.

We report a rare case of Adenomyoepithelioma (AME) of breast in association with Adenomyoepithelial adenosis (AA) in a 35 year old female.

Introduction

The myoepithelial cells are present in a
variety of proliferative lesions and in some malignant mammary tumours. The neoplasms of pure myoepithelial or epithelial myoepithelial origin are common and are well recognized in salivary glands and skin but are rare in other sites including breast.1 AME a biphasic tumour showing distinctive architectural growth pattern is identical morphologically and immunohistochemically to epithelial myoepithelial carcinoma of salivary gland.³

AA a lesion which to date has preceded or is an integral part of AME was formerly termed as Apocrine Adenosis.³

Case Report

A nonlactating 35 years female presented with a breast lump of two months duration which was diagnosed as fibroadenoma for which lumpectomy was performed. She had a normal contralateral breast and no axillary lymphadenopathy. Family history was noncontributory.

Pathological findings

Gross examination : The lumpectomy specimen measured 2 x 2 x 1.5 cm showed a circumscribed, encapsulated tumour with grey tan, lobulated cut surface with surrounding rim of breast tissue.

Microscopic examination - The histomorphology revealed a well circumscribed tumour composed of lobules made of glandular and solid elements (Fig. 1). The solid areas were composed of short fascicles of spindle cells with eosinophilic cytoplasm and elongated nuclei. The centres of these cellular aggregates contained glandular lumina lined by columnar cells with apocrine snouts. Spindle cells merged imperceptibly with outer row of glandular component (Fig. 2). At places the glandular element was predominant. The neoplastic glands had open lumina and were lined by two rows of cells. The luminal layer was formed by cuboidal to columnar cells with basally situated bland oval nuclei with inconspicuous nucleoli. The cytoplasm showed apocrine secretion. The outer row of cells was of oval to polygonal cells with round nuclei, clear cytoplasm and distinct basal lamina (Fig. 3).

There is no cellular atypia, mitotic activity, necrosis or haemorrhage. The intervening stroma showed collaginisation with the adjacent breast tissue showing cystic dilatation and mild epitheliosis.

Fig. 1 : Adenomyoepithelioma with lobulated appearance and pushing borders.		Fig. 2 : Slit-like tubules compressed by spindle celled myoepithelial component.
Fig. 3 : A focus of adenomyoepithelial adenosis with glands lined by two types of cells : epithelial and clear myoepithelial cell.

Discussion

Adenomyoepithelial tumours comprise a spectrum of neoplasms consisting of admixture of glandular and myoepithelial cells. According to recent WHO classification, spectrum of tumours included under this heading ranges from organoid, biphasic tumours with a combination of easily recognizable tubular formations and multilayered spindle celled myoepithelial elements to monophasic lesions with mesenchymal appearance.¹⁰

The first case was published by Hamperl in 1970.3 AME usually affects adult females in late reproductive life with an age range of 28 to 82 yrs.⁵ In all documented cases, patients present with a palpable nodule or mass ranging from 1-7 cm.⁶ In our case a 35 years, nonlactating lady noticed a palpable mass measuring 2 x 1.5 x 2 cms.

AME grossly shows a well circumscribed mass with a lobulated, greyish white to tan appearance and elastic to firm consistency.⁷ This case had a small, lobulated, solid, grey tan mass.

On microscopic examination, a definitive biphasic architecture with spectrum of growth patterns that is tubular, papillary, solid, trabecular and endocrine^2,4 is observed. Regardless of growth pattern, it is characterized by easily recognizableubule formation, presence of two cell types and multilayered spindle celled myoepithelial element.⁹

Breast AME frequently shows glandular proliferations characterized by roundish, glandular structures of varying size enclosing open lumina. The size of glands is 2-3 times larger than normal acini.8 Histologically we recognised similar biphsic pattern characterestic of AME with surrounding areas of adenomyoepithelial adenosis. The glands are lined by two types of cells inner tall columnar cells with granular, eosinophilic cytoplasm and outer row of clear myoepithelial cells. Some show apocrine snouts and outer row of flat or polygonal clear cells interposed between former and basal lamina.⁸ Histological appearance of AA simulates picture of Microglandular adenosis (MA) which enters into close differential diagnosis. Wherein uniform, round glands are seen in nonlobular pattern with absence of myoepithelial cells.^4,8 Tubular carcinoma is another D/D to be considered but tubules are irregular in size, shape and distribution. They are on an average some what larger than glands of MA, as well as variable but smaller than AA characterized by angular⁸ and tear drop shapes which contrasts glands of MA and AA. The glands in Tubular carcinoma are lined by cuboidal to columnar cells with apical snouts but lack myoepithelial layer as well as basal lamina. Desmoplastic stroma - a conspicuous feature of Tubular Carcinoma is absent in AA and MA.⁸

Lesions with monophasic spindle cell component in AME may resemble “fibromatosis like” lesions due to which it is taken into account in the differential diagnosis.⁹ But the presence of two types of glands amidst spindle cell proliferation points towards diagnosis of AME.

For clinical assessment the lesions are classified as benign, borderline and malignant.^6,10 Benign tumours have no cytological atypia, nor invasive growth pattern. Malignant tumours without obvious morpholgic glandular features are currently classified as malignant myoepithelioma or myoepithelial carcinoma. Histologically our case belongs to benign category, with no cytological atypia, no infiltrative borders and absence of necrosis. In all such benign cases close follow-up is a must as these tumours although appearing benign, tend to recur.6 Treatment is conservative surgery with close follow-up of the patient. Our patient was treated with lumpectomy and was followed up for six months without any recurrence.

References

1. Robert H. Young and Philip B. Clement Adenomyoepithelioma of Breast. American J Clinical Pathol 1988; 89 : 308-14.
2. Pia Foschini M, Reis Filho JS, et al. Salivary gland like tumours of Breast : Surgical and molecular pathology. J Clinical Pathology 2003; 56 :
   497-506.
3. Eusebi V Casadei GP, Bussolati G, Azzopardi JG. Adenomyoepithelioma of breast with a distinctive type of Apocrine Adenosis. Histopathology 1987; 11 : 305-15.
4. Maha Jabi, Irving Dardick, Nobert Cardigos. Adenomyoepithelioma of breast. Arch Pathol Lab Med 1988; 112 : 73-76.
5. Andrea Chang, Lawrence Bassett, Shakha Bose. Adenomyoepithelioma of Breast : A cytologic dilemma : Report of case and review of literature. Diagn Cytopathol 2002; 26 : 191-96.
6. Bernadette K Mclaren, Julia Smith BS, Peggy A. Adenomyoepithelioma : clinical, histologic and immunohistologic evaluation of a series of related lesions. American J Surg Pathol 2005; 29 :
   1294-99.
7. Amparo Saez, Teresa Serrano, Diego Azpeitia. Adenomyoepithelioma of Breast : Report of two cases. Arch Pathol Lab Med 1992; 116 : 36-3.
8. Vincenzo Eusebi, Maria P Foschchini, Christine M Betts. Microglandular adenosis, Apocrine Adenosis and Tubular Carcinoma of Breast. Am J Surg Pathol 1993; 17 (2) : 99-109.
9. Jeffrey, et al. Adenomyoepithelioma of Breast : A spectrum of biologic behaviour. Am J Surg Pathol 1992; 16 : 868.
10. Daniela Hangerman, Horst Buerger Christian Oehlschlegel Herman Herbst and Werner Boecker. Adenomyoepithelial tumours and myoepithelial carcinoma of breast : A spectrum of monophasic and tumours dominated by immature myoepithelial cells. BMC Cancer 2005; 5 : 92.
    

*Registrar; **Associate Professor; ***HOD; +Observer; LTMGH Sion Hospital, Mumbai 400 022