The clinical behavior of different molecular subtypes of breast cancer.

Background: Breast cancer is a heterogeneous group of tumors classified, according to different gene expressions that encodes for the hormone receptor status, into 4 main categories which are: luminal types A and B, triple negative/basal-like, and Her-2 molecular subtypes.

Patients And Methods: This retrospective study included 311 breast cancer females. Patients were classified according to the expression of hormone receptors into: Luminal-A, luminal-B, HER-2 enriched and basal-like types. All groups were then studied for differences in clinical course of the disease.

Results: Luminal-B type was the commonest molecular type (43.73%). Invasive ductal carcinoma was the commonest histological type (89.1%). Stages IIB and IIIA were the commonest clinical stages (24.4% & 22.2%) respectively. Most patients had no recurrence (85.5%), the commonest recurrence was local and axillary ones (7.1%). Low grade tumors were less frequent than intermediate and high grades (3.5%, 51.1%, and 45.3%). We found a significant correlation between molecular subtypes and survival status, tumor grade, and histopathological types (P values 0.029, 0.001, and 0.006) respectively, while it was not significant with age, BMI, recurrence & metastatic disease, overall survival, and TNM stage (P values 0.648, 0.398, 0.5, 0.063 and 0.319).

Conclusion: Luminal types A and B are the commonest molecular subtypes of breast cancer. Luminal type A is associated with improved survival, and basal like has the highest breast cancer fatality rates. Invasive ductal carcinomas of specific types mostly found in patients with luminal types A and B, while other rare forms like Paget's disease was diagnosed HER-2 enriched types.