Transdifferentiation of Secretory Carcinoma to Metaplastic Carcinoma at Metastatic Site

Area of Science:

• Oncology
• Pathology
• Genetics

Background:

• Secretory carcinoma is a rare breast tumor characterized by the ETV6::NTRK3 fusion gene.
• Early identification is crucial as patients may respond to TRK inhibitors.
• Treatment-induced morphologic changes in secretory carcinoma or other NTRK-driven tumors are not well-documented.

Purpose of the Study:

• To report a case of secretory carcinoma with treatment-induced transdifferentiation.
• To highlight the importance of identifying morphologic shifts in metastatic sites.
• To explore potential mechanisms of treatment resistance.

Main Methods:

• Histopathological examination of primary and metastatic tumor samples.
• Review of clinical data and treatment history.
• Correlation of morphologic findings with therapeutic interventions.

Main Results:

• A patient with secretory carcinoma exhibited transdifferentiation into metaplastic carcinoma (spindle cell and squamous cell) at the metastatic site after treatment.
• The morphologic shift occurred following therapeutic intervention.
• This transformation suggests a potential adaptive resistance mechanism.

Conclusions:

• Secretory carcinoma can undergo transdifferentiation into metaplastic carcinoma following treatment.
• Recognizing these morphologic changes is critical for accurate diagnosis and classification.
• Understanding these shifts aids in identifying mechanisms of resistance to targeted therapies like TRK inhibitors.