Synchronous malignancy is two or more histologically different malignancies detected within 6 months of the diagnosis of the first primary malignancy. Certain criteria have been laid down to diagnose synchronous malignancy; for example both the tumors should be malignant and neither should be a metastasis from the other, and the tumors should be separate from each other in terms of microscopic and morphologic features. The relationship and coincidence of breast cancer with thyroid disorders is a subject of extensive debate and controversy. Many studies have shown that thyroid diseases are common among women with breast cancer [1]. Breast carcinoma and thyroid carcinoma are the two most common malignancies that occur in women.

However, synchronous primary tumors of the thyroid and breast are very rare in clinical practice. Although differentiated thyroid and breast cancer carry a lower risk of death or disease recurrence than other malignancies, their incidences have been steadily increasing for at least 2 decades [1], and they have become the most common malignancies in females [2, 3]. Dual malignancy was first reported by Billroth in 1889 [4]. Here in, the present case report was a rare case of a 53 year old female who was diagnosed with synchronous primary papillary thyroid carcinoma and invasive ductal cancer of the breast. Ghosh et al also reported a rare case of a synchronous anaplastic carcinoma thyroid with ductal carcinoma breast [4].

In the month of May 2018, a 57 year old postmenopausal lady presented to the surgical oncology OPD with complaints of swelling in front of the neck for past one year. She had incidentally noticed a lump in the right breast for one month duration. On clinical examination the swelling in the neck moved with deglutition and overlying skin was intact. Local examination of the breast revealed no discharge from the nipple /retraction of the nipple. USG neck revealed, a large heteroechoic lesion in the right lobe of thyroid measuring 2.8X3 cms with vascularity and calcifications within, peripheral hypoechoic halo appears disrupted at some places. CT neck revealed diffuse enlargement of thyroid gland, a hypodense lesion noted in right lobe of thyroid measuring 3.5X3.3X4.3 cm.

B.

Figure 1: A.H & E X 100, shows neoplasm with characteristic nuclear features of papillary carcinoma thyroid. B. The tumor cells are (TTF -1) Thyroid Transcription Factor 1 positive (100x).

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Dual malignancy was first reported by Billroth in 1889 [4]. According to the guidelines, these two malignancies can be synchronous but should not be metachronous [5, 6]. Both the tumors should be malignant and neither should be a metastasis from the other. According to the guidelines, the incidence of a second primary tumor in cancer patients is approximately 10% [5, 7]. Previous studies have mainly focused on possible increases in the incidence of contralateral breast carcinoma. However, the risk of concurrent thyroid carcinoma among women with breast cancer has not been explored in recent years [8]. Analysis of the USA National Cancer Institute's Surveillance, Epidemiology, and End Results data has demonstrated that the incidence of thyroid cancer is higher in patients with a pre-existing malignancy than in patients without a preexisting malignancy and that the incidence of other malignancies is higher in patients with thyroid cancer than in patients without thyroid cancer [9], findings consistent with the current guidelines [5]. A previous study revealed that a history of any thyroid disorder or subsequent treatment was not associated with an increased risk of developing breast cancer.

Additionally, previous studies have suggested that amplified levels of nuclear protein 1 [14], retinoid-inducible nuclear factor [15] and nuclear receptor co-activator [16] in the breast served as potential oncogenic co-activators of and biomarkers for thyroid and breast cancers. Furthermore, it has been reported that the risk of synchronous thyroid and breast cancer is associated with Cowden syndrome and Cowden-like syndrome, which usually cause multiple cancers via flavin adenine dinucleotide (FAD)/nicotinamide adenine dinucleotide (NAD)-dependent destabilization of P53 [17]. According to one of the recent retrospective study by IIkel et al, Increased risk of breast cancer in follow-up period of thyroid cancer or vice versa has been reported. However, they have some associations, synchronous presentation of these tumors is rare and they presented 12 patients diagnosed as breast and thyroid cancer and treated at the same time, and they observed that they were common among post menopausal women, similar to the present case and most common among them being papillary carcinoma thyroid [3].

Although synchronous primary tumors of the thyroid and breast are very rare, they remain a possibility, therefore more attention should be paid to these cancer, especially in elderly postmenopausal women and association of these tumors should be evaluated by large scaled studies.