An Inherited Cancer Syndrome Due to a Germline Monoallelic EGFR Mutation with Loss of Heterozygosity in Lung and Breast Tumors

The epidermal growth factor receptor (EGFR) exon-19 deletion is one of the most common mutations detected in lung cancer patients. Although exon-19 deletion is frequently detected in adenocarcinoma, observing this mutation in germline cells is very rare. Besides, the co-occurrence of homozygous and heterozygous mutations in dual primary cancers in a person is very uncommon. This article presents a 53-year-old Iranian woman with no history of smoking who was diagnose with two primary cancers; invasive ductal carcinoma, and primary pulmonary lung adenocarcinoma. The case reported a history of breast cancer in her sister and a history of lung cancer in her father. To select the best choice of treatment the EGFR gene was analyzed with Sanger’s sequencing method from DNA extracted from the patient’s lung tissue sample. Observing two primary cancers in this patient and considering her family pedigree, germline cells were also analyzed using samples recruited from the patient’s peripheral blood to investigate any EGFR mutations in her germline cells. The obtained data revealed that the lung tissue of the patient carried a homozygous form of EGFR exon-19 deletion while her peripheral blood contained a heterozygous form of this mutation, which is exceptionally rare.