Endocrine Abstracts

Introduction: CHEK2 mutations are associated with increased risk of having neoplasms of various organs, including thyroid, breast, colon, renal and ovarian cancers. Coexistence of thyroid and breast cancers was observed in female carriers of CHEK2 gene mutations. In polish population the most common mutations are those truncating CHEK2 protein (1100delC, IVS2+1G>A, del5395) and a missense I157T CHEK2 mutation. Carrying missense I157T mutation is connected with having twice the risk of getting papillary thyroid cancer in polish population whereas mutations truncating CHEK2 protein increase the risk by five times.

Case series: 1) 63-year-old female patient after total thyroidectomy because of multifocal papillary thyroid cancer in 2014, after surgery in 2002 and subsequent hormonal therapy because of left-sided breast cancer and after surgery because of sigmoid colon cancer in 2013. In family history – mother suffered from breast cancer. Molecular testing revealed missense I157T mutation of CHEK2 gene.

2) Female patient, operated in 2013 at the age of 44 for multifocal papillary thyroid cancer with metastases to the left-sided cervical lymph nodes. In October 2013 the patient was diagnosed with invasive ductal left-sided breast cancer with metastasis to the left axillary lymph node. She was treated with breast amputation, radiotherapy and hormonal therapy. Molecular testing revealed missense I157T mutation of CHEK2 gene.

3) 60-year-old female patient after total thyroidectomy in 2017 because of papillary thyroid cancer, after right-sided mastectomy in 2010 because of breast cancer and after surgery because of endometrial cancer in 2011. Molecular testing revealed CHEK2 protein truncating mutation.

4) 49-year-old female patient after total thyroidectomy in 2017 because of papillary thyroid microcarcinoma, after left-sided mastectomy in 2015 because of breast cancer. Molecular testing revealed CHEK2 protein truncating mutation.

Conclusions: 1) In consideration of possible coexistence of thyroid and breast cancers, in case of diagnosing one of them, it is advised to perform diagnostics and observation to identify possible development of the other neoplasm.

2) In patients with CHEK2 gene mutation we need to remember about higher risk of papillary thyroid cancer and possibility of concomitant malignancies especially breast cancer.