Overdiagnosis of lobular carcinoma of breast- A review of histomorphological features and immunohistochemistry: A case series

Abstract

: Invasive lobular carcinoma (ILC) accounts for 5%–15% of all invasive breast cancers (BCs) and is the second most common type of BC behind invasive ductal carcinoma (IDC) of no special type. ILC of the breast is characterized morphologically by small, noncohesive cells that infiltrate the stroma in a single-file pattern(Indian file pattern). ILC tumours display features associated with a good prognosis, being low grade, oestrogen receptor positive and is mainly associated with the complete loss of E-cadherin (E-cad) expression.To review the cases of invasive lobular carcinoma and to immunohistochemically categorize IDC and ILC.This is a retrospective study including all the modified radical mastectomy cases of invasive lobular carcinoma of breast reported in the department of Pathology of a tertiary care centre from January 2021 to January 2022. Histopathological and immunohistochemical analysis of those cases were reviewed.We encountered 10 cases of invasive lobular carcinoma of breast from January 2021 to January 2022. The average age of the patients was 55.9 years old (35–72). The classic presentation was a breast lump found in 100% of the cases. On physical examination, breast carcinoma was suspected in all the patients. The average size of the tumours was 4.5 cm (1.4– 9cm). Out of those 10 cases, 4 cases were right sided lesion and modified radical mastectomy was performed in all the 10 cases. All the 10 cases were diagnosed as invasive lobular carcinoma on histopathology and review of those cases showed 7 out of 10 cases to be IDC. Those cases showed pitfalls in histomorphological analysis which were later confirmed by immunohistochemistry. The findings are presented in the study.Our study found that there was a histomorphological pitfall in the diagnosis of IDC. In ambiguous cases with histologically equivocal features, a strong, complete, membranous E-cadherin expression may help in resolving the problem and in aiding in the subclassification of invasive breast carcinoma.