Solid Papillary Carcinoma of Breast: Clinicopathologic Comparison With Conventional Ductal Carcinoma of Breast.

Introduction Solid papillary carcinoma (SPC) is a distinct rare subtype of breast tumour that often exhibits a neuroendocrine differentiation. Due to the rarity of these tumours, few studies have assessed the clinicopathological features of these tumours. Therefore, in this study, we evaluated the clinical and pathological profiles of SPC and compared the pathologic features with conventional invasive ductal carcinoma (IDC) in our population. Methods It was a retrospective cross-sectional study conducted at Liaquat National Hospital and Medical College from January 2013 until December 2019 over seven years. Cases with histological diagnosis of SPC and IDC were included in the study, and clinicopathological characteristics were compared. Results We included 39 cases of SPC in our study diagnosed during the study period. During the same timeline, 634 cases of IDC were reported and therefore included in the study for comparison. The mean age of the patients with SPC was 53.97 ± 12.15 years, and the mean tumour size was 3.42 ± 1.87 cm. Axillary metastasis was noted in 15.4% of cases. 94.9% of cases of SPC were invasive. Estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor-2 (HER2/neu) and synaptophysin positivity was seen in 84.6%, 87.2%, 10.3%, and 59% respectively. Recurrence was noted in 10.3% of cases with 94.9% survival rate. Cases of SPC had significantly lower grade (grade I + II), tumour (T) and nodal (N) stage than IDC. Moreover, the frequency of hormonal receptor expression (ER and PR) was higher, and the frequency of human epidermal growth factor receptor 2 (HER2/neu) expression was lower compared to IDC. Conclusion SPC is a distinct variant of malignant papillary breast tumours with overall better prognostic parameters than IDC. Therefore, it is essential to recognize the histological features of this rare breast tumour.