Extensive dystrophic calcinosis in dermatomyositis with concurrent breast carcinoma: an imaging pitfall

Dermatomyositis is a rare idiopathic inflammatory myopathy. Long-standing disease may be complicated by progressive dystrophic calcinosis. The association of extensive calcinosis with underlying malignancy remains exceptionally rare and diagnostically challenging. A 63-year-old woman with a 15-year history of dermatomyositis presented with rapidly progressive diffuse cutaneous calcinosis and a palpable right breast mass. Mammography identified a spiculated mass classified BI-RADS 5, embedded within extensive mammary macrocalcifications. Ultrasound-guided core needle biopsy confirmed invasive carcinoma of no special type (NST) (SBR grade II, ER−/PR−, HER2−). Staging CT scan and bone scintigraphy demonstrated no distant metastasis but revealed diffuse soft-tissue calcinosis of the abdominal and pelvic walls. The patient was subsequently referred to the oncology department for further staging and multidisciplinary management. This case highlights the diagnostic pitfall of extensive mammary calcinosis in DM, which may obscure an underlying mass or architectural distortion rather than directly mimic malignant microcalcifications. Any discrete mass or architectural distortion identified within or adjacent to a calcinotic background warrants targeted ultrasound and image-guided biopsy. Oncological surveillance in dermatomyositis should be age-appropriate and risk-stratified, reflecting the fact that malignancy risk is highest around the time of diagnosis.