Presence of Basement Membrane Material around the Tubules of Tubulolobular Carcinoma

BACKGROUND: Core needle biopsies represent only a small portion of a breast lesion. Rare lesions with overlapping features may be underestimated in such small samples. CASE REPORT: A 67-year-old female underwent core needle biopsy of a 27-mm breast tumour demonstrating infiltrative glands without significant desmoplasia. Periglandular collagen IV immunostaining and the small glands were reminiscent of microglandular adenosis, and despite the infiltrative look of the microglands, the lesion was interpreted as suspicious for malignancy. Finally, the tumour proved to be a tubulolobular carcinoma. CONCLUSIONS: The tubules of tubulolobular carcinoma may show a basement membrane-like staining pattern with collagen IV, and this must be considered in the differential diagnosis of mammary lesions with small glandular architecture.