Nodular basement membrane deposits in breast carcinoma and atypical ductal hyperplasia: mimics of collagenous spherulosis.

Collagenous spherulosis is characterised histologically by the accumulation of hyaline globules containing basement membrane components. Originally described in the breast, it has also been found in skin and salivary gland neoplasms. In the breast it has hitherto always been associated with benign disease and reports have asserted that this is invariably the case, cautioning against the diagnosis of malignancy when the condition is seen. We present here five cases with similar appearances to collagenous spherulosis in routine histology and immunohistochemistry, and ultrastructural studies in one of them, in which the condition was not associated with simple benign breast disease. Two of the cases were associated with invasive carcinomas of unusual histological types, one with intracystic papillary carcinoma, one with comedo ductal carcinoma-in-situ and one with atypical ductal hyperplasia. We suggest that appearances similar to collagenous spherulosis can be associated, either through being formed by a lesion or by collision, with malignancy and warn that on encountering the lesions the pathologist must not assume, as suggested in previous accounts, that it denotes a benign process. This is an important observation since collagenous spherulosis is likely to be encountered more frequently in the range of lesions biopsied in national breast screening programs.