Metaplastic carcinoma of the breast arising within complex sclerosing lesion: a report of five cases

Aims: This study presents a series of five cases in which metaplastic carci noma, predominantly low-grade adenosquamous carcinoma, of the breast is see n arising within a background of a complex sclerosing lesion. This associat ion has been recognized previously but has not been documented in detail. T his study describes the characteristics of the components present in each c ase and discusses the existing literature. This observation adds further ev idence to support an association between some types of invasive breast carc inoma and sclerosing lesions of the breast. Methods and results: Four of these cases were received as referral cases fo r opinion. The fifth was received as part of the routine surgical workload within our own institution. Two patients presented following mammographic s creening and three symptomatically; their mean age was 62 years (range 49-6 8). The mean lesion size was 16 mm (range 7-24). All five lesions showed fe atures of a complex sclerosing lesion/radial scar in the form of central sc lerosis with elastosis and radiating benign entrapped tubules. One had asso ciated benign papillary structures and two had focal benign squamous mletap lasia. Four cases showed coexisting but distinct areas of low-grade adenosq uamous carcinoma with glandular and squamous epithelial differentiation in a spindle cell background. One case had associated undifferentiated spindle cell carcinoma. Detailed immunophenotypic characteristics of two cases are presented. Conclusions: This series illustrates a postulated but previously unconfirme d association between an unusual form of metaplastic breast carcinoma (aden osquamous carcinoma) and complex sclerosing lesions. The mechanisms of indu ction of breast carcinoma are poorly understood but these observations furt her emphasize the potential for sclerosing lesion of the breast to be assoc iated with, and possibly give rise to, invasive carcinoma of different type s. The precise nature of the interaction between the pathological processes remains unclear.