In this study, although bilaterality was seen only in cases with secondary involvement, no marked difference was observed between primary and secondary breast involvement of hematological malignancies. Hematological malignancies may mimic both benign breast lesions due to an oval-round shape, circumscribed margins, posterior acoustic enhancement, and breast carcinoma, especially inflammatory breast carcinoma, because of skin thickening, axillary lymphadenopathy, irregular shape, and non-circumscribed margins. The absence of microcalcification and posterior shadowing, and markedly low ADC values can differentiate breast carcinoma.
Although some previous studies have reported that primary breast lymphoma manifests at a larger size with a worse prognosis and at an earlier age than secondary breast lymphoma [3, 6], the current study results were the opposite of these findings. Of the total nine deaths, eight were secondary involvement of the breast. The only death from primary breast involvement was the oldest patient (83 years old) in the group. These differences may be a result of the fact that the current study patient group included different hematological diseases such as granulocytic sarcoma and plasmacytoma. No marked difference was observed between primary and secondary breast involvement of hematological malignancies except that bilaterality was only seen in secondary involvement. Similar to these findings, Genco et al. also reported no significant difference between patients with primary and secondary breast lymphoma [7]. The most common presenting symptoms were neck and axillary masses before breast involvement in the cases with secondary diseases, while the patients with primary breast lymphoma did not have any symptoms except breast or axillary masses. Our two patients with secondary breast involvement of hematological malignancies had thrombocytopenia at the time of diagnosis. Besides thrombocytopenia due to hematological disease, chemotherapy can cause low blood cell counts. So, radiologists should check the laboratory results before breast biopsy and be careful during a biopsy in terms of bleeding and infection in these patients. In a comprehensive literature review, it has been reported that platelet count greater than 25,000 μ/L and INR less than 2.0 are appropriate for radiological procedures such as tissue biopsy and percutaneous catheter placement [8].
Hematological malignancies may mimic benign breast lesions radiologically because of the oval-round shape, circumscribed margins, and posterior acoustic enhancement. The presence of hyperechoic areas within the masses can be even more confusing and may resemble hamartoma [4] (Fig. 1). However, a history of size increase in breast lump, axillary lymphadenopathy, and skin thickening should raise suspicion of malignancy. In contrast, similar radiological findings mimicking benign breast lesions can be seen in high-grade triple-negative breast cancers or mucinous and medullary breast carcinoma [9, 10]. Posterior acoustic enhancement can occur in high-grade triple-negative breast cancers due to necrosis and high cellularity. Also, the rapid growth of triple-negative high-grade breast cancers can lead to low stromal reaction and consequently oval-round shape and circumscribed margins [9, 11, 12]. For similar reasons, posterior acoustic enhancement, oval-round shape, and circumscribed margins may be seen in hematological malignancies of the breast.
Hematological malignancies may also resemble breast carcinoma, especially inflammatory breast carcinoma, because of skin thickening, axillary lymphadenopathy, irregular shape, and non-circumscribed margins (Fig. 2). Skin thickening without a mass can also be seen in patients with breast lymphoma [3]. Skin thickening can be caused by tumor involvement in the dermal lymphatics of the breast, lymphangitic metastasis to the breast, or lymphatic drainage obstruction [13]. Unlike breast cancer, posterior shadowing and microcalcification are not observed in breast involvement of hematological malignancies. Although the final diagnosis is performed histopathologically, familiarity with the radiological features of hematological malignancies can help to establish an accurate diagnosis. Misdiagnosis as breast carcinoma can result in inappropriate treatment such as breast and nodal surgery.
According to the MRI findings in this study, hematological malignancies showed T2 hyperintensity, type 2 or 3 dynamic curves, and marked diffusion restriction (Fig. 3). Hyperintensity on T2-weighted images suggests a benign lesion, while type 2 and 3 dynamic curves are usually seen in malignant lesions [14]. Dynamic curves can help to distinguish hematological malignancies from benign lesions. But, they cannot help differentiation from typical breast cancers which usually show type 2 or 3 dynamic curves. Most invasive carcinomas of the breast are hypointense or isointense relative to fibroglandular tissue. T2 hyperintensity may occur due to necrosis and inflammation associated with necrosis. Inflammation causes stromal edema within the tumor and T2 hyperintensity [15]. T2 hyperintensity can also be observed diffusely secondary to diffuse edema caused by lymphatic obstruction. Although diffusion restriction is generally observed in malignant diseases, ADC values may be lower in hematological diseases compared to breast cancer. Similar to the findings of Zhou et al. [6], the current study ADC values in hematological diseases (mean ADC 0.585 × 10−3) were lower than the ADC values reported in published literature for breast carcinoma (ranging from 0.9 to 1.2 × 10−3) [16, 17]. This result may have been due to the hypercellularity and small extracellular spaces of hematological malignancies. Compared to typical breast cancers, very low ADC values and T2 hyperintensity may suggest hematological malignancies.
There were some limitations of the current study. The major limitation was the limited number of cases due to the rarity of breast involvement of hematological malignancies. Secondly, our study was a retrospective study. Because of the retrospective nature of it, all imaging features including Doppler and mammography were not applicable for all patients. Finally, some clinical data such as follow-up were missing due to retrospective design.