Establishing a histologic basis for false-negative mammograms.

In order to explore the histology of false-negative mammograms, 264 consecutive patients with breast cancer were retrospectively reviewed until 100 patients with palpable cancers were identified. These patients were imaged by a dedicated mammographer within 6 months prior to biopsy. Nine of the 100 patients had "negative" readings originally, with 6 of the 9 still regarded as negative when re-examined after full knowledge of the tumor location. Histologic review of these six tumors showed a diffusely infiltrative pattern in five patients (three with invasive lobular carcinomas and two with multifocal, invasive ductal carcinomas). Although background breast density always serves in a critical relationship with tumor density on film, only one of these six patients showed a severe degree of mammographic breast density. Diffuse histology should be recognized as a principal cause of false-negative mammograms. Since mammography is based solely on anatomic contrasts, diffuse histology could easily prevent the perfection of this modality, calling attention to the need for improved adjunct imaging techniques.