Metaplastic carcinoma of the breast with transformation from adenosquamous carcinoma to osteosarcomatoid and spindle cell morphology

Abstract

Metaplastic carcinoma of the breast refers to a heterogenous group of mammary carcinomas that contain a mixture of various cell types, including squamous cells, spindle cells and/or a mesenchymal component, such as bone or cartilage. To the best of our knowledge, the clinical course of a tumour that has undergone a transformation from one type of metaplastic carcinoma to another subtype has not previously been reported. The present study reports the five-year clinical and pathological course of a metaplastic breast carcinoma in a 55-year-old female, who was diagnosed with a sclerosing fibroadenomatous nodule with osseous metaplasia and focal atypia. A recurrent tumour was documented four years later, showing a predominant component of osteosarcoma with adenosquamous carcinoma. Upon pathological review of the initial mass, the diagnosis was changed to low-grade adenosquamous carcinoma. The patient was treated with breast conserving therapy. However, one year later, a recurrent metaplastic carcinoma with spindle cell morphology was documented and surgically removed by mastectomy. Subsequently, pulmonary invasion of the chest wall occurred and the patient eventually succumbed due to the invasive nature of the disease.

Keywords: adenosquamous; breast; metaplastic carcinoma; osteosarcoma; spindle cell.

Figure 1

(A) Mammography performed in 2005. CC and MLO views show an oval, well-circumscribed mass, isodensity with a rim and calcification. (B) Mammography performed in 2009. CC and MLO views show a large calcified mass at the left inferior inner quadrant. The magnified pictures reveal the sunburst appearance, which resembled osteosarcoma calcification. (C) Mammography performed in 2010. CC and MLO views show a well-defined 1.5-cm mass with multiple coarse calcifications underneath the surgical scar. CC, cranio-caudal; MLO, medio-lateral oblique.

Figure 2

(A–C) First mass removed in 2005. (A) Low-grade adenosquamous carcinoma with focal osseous metaplasia, initially diagnosed as nonmalignant fibroadenomatous nodule (H&E). (B) Presence of banal-appearing epithelial component in fibromyxoid stroma (H&E; magnification, ×200). (C) Low-grade angulated tubules and irregular squamous nests (H&E; magnification, ×400). (D and E) Recurrent tumor in 2009. (D) Prominent osteosarcomatous component with few entrapped glands (H&E; magnification, ×200). (E) Entrapped squamous epithelium (H&E; magnification, ×200). (F and G) Recurrent tumor in 2010. (F) Focal osseous component (H&E; magnification, ×40). (G) Predominant spindle cell morphology without any epithelial cells documented (H&E; magnification, ×400). H&E, hematoxylin and eosin.