Monckeberg medial calcific sclerosis (MCS) is a ring-like calcification of the vascular media of small to medium sized vessels without associated intimal thickening. Almost exclusively, MCS is the underlying condition in what is referred to as breast arterial calcification (BAC) detected at mammography. BAC is a relatively common finding. The classic radiographic pattern of BAC is the “railroad track” pattern, which appears as linear parallel calcifications, and is a reflection of the circumferential pattern of calcification in MCS¹; it is easily interpreted as benign.

We recently encountered an atypical microcalcification pattern of MCS mimicking malignancy in a 64 year old woman discovered at routine mammography. She had no risk factors for breast cancer. There was no history of breast trauma or surgery, renal disease, or parathyroid problems. The patient had non-insulin dependent diabetes mellitus. Coronary artery disease was present as identified by an episode of retrostrenal chest pain and a stress test showed ST segment elevation in the electrocardiogram. No palpable abnormalities were present in the breast or axilla.

This atypical pattern was present together with popcorn-like calcification of a hyalinised fibroadenoma and typical benign microcalcifications. The atypical calcification was present as medium to high density clustered calcifications in a curved and branching pattern. This pattern is usually caused by calcium phosphate, and is typically associated with malignancy, compared with low density amorphous calcifications, which are caused by calcium oxalate, and are associated with benign conditions.¹

Wire localised excision of the clustered calcifications was performed and the specimen radiographs showed that suspicious microcalcification clusters were included in a block. Sections corresponding to suspicious microcalcifications had Monckeberg medial calcific sclerosis in small to medium sized vessels. These were both ring-like classic circumferential areas of calcification and discontinuous calcification foci in arterial media.

This atypical pattern posing a diagnostic dilemma requires excision for histopathological assessment. It has been reported earlier,^2,3 and is probably caused by non-circumferential and discontinuous foci of calcification in the vascular media; these calcific microliths are probably seen in the early stages of development of MCS,² and may mimic linear, curved, or branching patterns of microcalcification clusters indicating malignancy.⁴

The pathogenesis of MCS/BAC is thought to be related to several factors, including age related change, diabetes mellitus, chronic renal failure, and coronary artery disease.

Pecchi et al showed that the presence and severity of BAC strongly correlated with the extent of coronary atherosclerosis, as determined by the amount of coronary calcium detected by multislice computed tomography,⁵ and BAC may indeed be a surrogate marker of coronary artery disease. Although coronary artery disease is almost always the result of intimal atherosclerosis, a disease different from MCS, the association may be reflective of shared pathways of calcium deposition.

In summary, this report highlights the atypical calcification pattern of Monckeberg medial calcific sclerosis mimicking malignant calcifications in breast requiring excision for diagnosis. This benign vascular calcification may also be a marker of coronary artery disease.