Collagenous spherulosis (CS) of the breast is a benign lesion most frequently associated with other benign proliferative processes, including papilloma, papillary duct hyperplasia, radial sclerosing lesions, sclerosing adenosis, and atypical ductal hyperplasia. Originally reported by Clement et al. in 1987, the lesion was first described as an incidental microscopic finding of intraluminal clusters of collagen-rich, eosinophilic, or star-shaped fibrillar spherules (Clement et al. 1987).
Incidence: Collagenous spherulosis (CS) is very rare, with an estimated incidence of less than 1% in excisional specimens (Resetkova et al. 2006) and about 0.2% in cytology material (Sola Perez et al. 1993). CS may go unrecognized in about 48% of cases or may be misdiagnosed as atypical hyperplasia in 17% of cases or as in situ and/or invasive carcinoma in 11% of cases (Mooney et al. 1999).
Age and sex: The patients were all women ranging in age from 36 to 90 years (mean age, 52 years; median age, 50 years) in the largest published study (Resetkova et al. 2006).
Treatment and outcome: Although rare, CS is a distinct, morphologically well-defined entity most often reported in association with benign proliferative changes. Processes most frequently associated with collagenous spherulosis lesions include columnar cell hyperplasia, radial scar, sclerosing adenosis, papillomas, ductal hyperplasia without atypia, and adenomyoepithelioma (Reis-Filho et al. 2004). Less frequently, CS has been observed in specimens with a concurrent malignant process, most commonly lobular carcinoma in situ (LCIS) (Resetkova et al. 2006; Mooney et al. 1999). Association of CS with LCIS and other benign and malignant breast lesions is interpreted as most likely coincidental. CS could present as a mammographically suspicious mass or density and could be associated with microcalcifications. Treatment of the patient and clinical outcome of CS is dependent on accompanying breast lesion.
CS is an incidental finding in breast samples removed for other reasons, and it is not visible at macroscopy.
Cribriform architecture characterizes, in addition to CS, a broad spectrum of benign and malignant proliferations in the breast, chiefly invasive cribriform carcinoma, ductal carcinoma in situ, and adenoid cystic carcinoma (AdCC) (“Adenoid Cystic Carcinoma”). The differential diagnosis can be especially challenging in needle core biopsies (Rabban et al. 2006).
AdCC of the breast is a rare, special type of invasive breast carcinoma, accounting for 0.05–0.10% of all primary carcinomas of the breast. The myoepithelial immunophenotypic overlap between cribriform pattern AdCC of the breast and CS could lead to diagnostic pitfalls in evaluating cribriform lesions of the breast, especially in core needle biopsies. While smooth muscle actin and p63 are expressed by both entities, other myoepithelial markers, calponin and smooth muscle myosin heavy chain, are expressed only by CS and thus can be used to distinguish it from AdCC (Reis-Filho et al. 2004). In contrast, the staining for c-kit and EMA may facilitate identification of the ductules characteristic for AdCC.
References and Further Reading
- Mooney, E. E., Kayani, N., & Tavassoli, F. A. (1999). Spherulosis of the breast. A spectrum of mucinous and collagenous lesions. Archives of Pathology & Laboratory Medicine, 123, 626–630.Google Scholar