Discussion:
In the autopsy of patients with breast cancer, the risk of spleen involvement has been 11-17%, which is uncommon compared to metastasis to other organs. In contrast, the most common organ of metastasis is the lung with a risk of 57-77% (4).
In the study by Corinna in the autopsy of patients with cancer, metastasis to the spleen has been more common among younger patients and in those with more sites of metastasis (2), while in our case, the spleen has been the only site of metastasis.
Metastasis to the spleen occurs in a delayed way and rarely becomes symptomatic; thus it is seldom diagnosed by the physician (5). However, in our case, metastasis to the spleen was early and synchronous with the primary breast cancer as well as symptomatic with splenomegaly presentation. Various etiologies have been propounded for splenomegaly, including hepatic diseases, malignancies including lymphoma and leukemia, splenic vein thrombosis, cytopenia (which causes functional splenomegaly), infections, splenic sequestration, connective tissues disease, and focal lesions such as hemangioma, abscesses, cysts, and metastasis (3).
For diagnosis of splenomegaly, a CT scan and sonography can be used. MRI, PET scan, biopsy, splenectomy, and liver-spleen colloid scanning are recommended in special cases (3).
In two cases reported by Cummings et al., the primary symptoms of patients who had metastasis to the spleen were ITP (due to diffuse splenic metastases), and the absence of any specific tumors in the imaging complicates the diagnosis. In these two cases, the patients had also metastases to the bone, and the spleen metastasis was delayed (6).
In the literature review, there are sparse studies on metastasis to the spleen with breast origin, and most metastases are multiple as well as multiorgan. In the study by Bartolotti, one case of breast cancer who had metastasis to the lymph node, lungs, and vertebrates at the time of diagnosis experienced a relapse in the spleen after four years; in the CT scan, it was in the form of two focal lesions and was diagnosed with FNA. The patient underwent chemotherapy (7).
Nevertheless, regarding solitary metastasis to the spleen with breast origin, we found only five case reports in the literature, which were as follows:
The first case was found in 2001; a breast cancer who experienced solitary metastasis to the spleen after 9 years (8).
S IYPE Case in 2002; she was a 54-year-old woman who found solitary metastasis to the spleen after 2 years, and underwent splenectomy (9).
Kari Sufficool et al. in 2012 reported synchronous metastasis to the spleen with breast origin diagnosed through FNA (10).
In 2013, a woman with breast cancer was reported; after the treatment and in the follow-up was examined due to abdominal pain and fever, for whom metastasis to the spleen was diagnosed. She passed away 3 months after due to unknown reasons (11).
In 2019, Sohaila Fatima et al. reported a 62-year-old breast cancer case (ILC) with synchronous solitary metastasis to the spleen, who underwent chemotherapy (12).
A case of hairy cell leukemia and breast cancer have been reported in 2013. The patient was a 65-year-old woman with the diagnosis of breast cancer who was treated with surgery and chemotherapy. About 20 years later, hairy cell leukemia was confirmed by cytopenia in the complete blood count and BMB(13).
This case has been reported considering the uncommonness of solitary metastasis to the spleen from breast cancer origin as well as synchronous hairy cell leukemia.