Invasive lobular carcinoma (ILC) is a common subtype of breast cancer diagnoses, accounting for up to 15% of breast cancer cases. This case report will discuss the unusual presentation of a patient with histopathological findings of ILC and associated non-conventional imaging findings. Patient consent for the writing of this case report and photographs included was obtained.  

A 74-year-old woman was referred to the Breast clinic with a 2-month history of worsening left-sided nipple retraction. She has no prior history or family history of breast disease or cancer. On initial assessment, the breasts appeared normal on inspection, apart from left-sided nipple retraction. There were no palpable breast or axillary masses. Mammogram and ultrasound did not detect any significant abnormalities apart from some generalised increased breast parenchymal enhancement in the middle and posterior third, extending into the left axillary tail. There was no evidence of axillary lymphadenopathy. Breast density was calculated as BIRADSB.

Further investigation with MRI breasts was performed showing significant oedema and inflammatory changes in the lateral left breast and left pectoralis muscles without convincing evidence of a breast or axillary lesion. CT chest 1-month later revealed persistent oedema and stranding in the posterior one-third of the left breast extending to the upper outer quadrant and left axilla. The patient’s case was taken to an MDT discussion and a decision was made to perform a left-sided pectoral muscle biopsy. Several core biopsies were taken, and histopathological assessment revealed an invasive lobular carcinoma with the following immunophenotype: ER8, PR 0, Ki-67 10%, HER2 negative (IHC 1+).

This case presents particular challenges in patients with breast cancer with no discrete breast lesion to remove. The mainstay of this patient’s treatment is via endocrine and systemic therapy.