Description

Invasive lobular cancer (ILC) constitutes 15-20% of all breast cancers. Pure ILC is usually described when more than 90% of the tumour consists of the lobular component. The tumour tends to infiltrate diffusely thus making clinical assessment difficult. As ILC may not form a discrete mass, cause little architectural distortion and rarely calcifies, radiological investigation may be unhelpful in pre-operative diagnosis. Fine needle aspiration cytology has a limited overall accuracy as the malignant cells are small with round nuclei and scanty cytoplasm showing little pleomorphism. Wide bore needle biopsy may be more useful in achieving a tissue diagnosis to plan surgical management. Up to 30% of ILC may be multicentric or bilateral. Breast conservation surgery remains the surgical treatment of choice, although complete surgical excision should be obtained and may require mastectomy. The development of metachronous ILC does not appear to be associated with a worse prognosis. Adjuvant therapy is offered along the same lines as invasive ductal cancer. Approximately 90% of ILC is hormone sensitive and should be offered adjuvant endocrine therapy. The metastatic pattern of ILC may include unusual sites and a high index of suspicion facilitates early diagnosis of progressive disease.