Geetha Patil Okaly۱ - Department of Pathology, Kidwai Memorial Institute of Oncology, Bangalore, India
Akshatha C - Department of Pathology, Kidwai Memorial Institute of Oncology, Bangalore, India
Sandhya N - Department of Pathology, Kidwai Memorial Institute of Oncology, Bangalore, India
Akina Prakash - Department of Pathology, Kidwai Memorial Institute of Oncology, Bangalore, India
M Suma - Department of Pathology, Kidwai Memorial Institute of Oncology, Bangalore, India
Ashwini Nargund - Department of Pathology, Kidwai Memorial Institute of Oncology, Bangalore, India
Shankar Anand - Department of Pathology, Kidwai Memorial Institute of Oncology, Bangalore, India
C Ramachandra - Department of Surgical Oncology, Kidwai Memorial Institute of Oncology, Bangalore, India
Libin Cherian - Department of Pathology, Kidwai Memorial Institute of Oncology, Bangalore, India

Background & Objective: Metaplastic carcinoma is a diverse variant of invasive breast carcinomas (IBC) characterized by dedifferentiation of malignant cells towards squamous and/or mesenchymal elements. It accounts for ۰.۳-۱.۲% of all IBC. These tumors are typically triple-negative by hormonal profiling with a high proliferation index and a dismal prognosis. Lymph node metastasis is an unusual feature in metaplastic carcinoma.Methods: The present study analyses ۳۰ cases (۲۶ cases of modified radical mastectomy and ۴ cases of lumpectomy) of metaplastic carcinoma over ۲۰۱۸-۲۰۲۰ (۳ years). Four oncopathologists reviewed routine histopathologic and immunohistochemical-stained slides. The clinical details were collected from the Medical Records Department of the Cancer Institute.Results: A total of ۲۰ (۶۶.۶۷%) cases were patients >۵۰ years of age, ۲۱(۷۰%) out of which were diagnosed as invasive carcinoma, grade ۳ according to the Nottingham histological score. Five (۱۶.۷%) cases presented with lymph node metastasis. While immunohistochemically ۲۸ (۹۳.۳%) cases were triple-negativeCK۵/۶, P۶۳, EGFR, and Ki-۶۷ (more than ۴۰%) positivity was noted in ۲۵ (۸۳.۳%) , ۲۶ (۸۶,۷%) , ۲۰ (۶۶.۷%), and ۲۵ (۸۳.۳%) cases, respectively.Conclusion: Metaplastic carcinoma is characteristically triple-negative breast malignancies (TNBC) exhibiting a high Ki-۶۷ index and a lower rate of lymph node metastasis. CK۵/۶, p۶۳, and EGFR are pertinent immunohistochemical markers that may aid in diagnosis. However, those markers are non-specific for the disease and morphologic features are always the key to the diagnosis of the process.

CK: cytokeratin, EGFR: epidermal growth factor receptor, IBC: Invasive breast carcinoma, IHC: immunohistochemistry, NST: No special type, MC: Metaplastic carcinoma