Metastatic cardiac tumor from urothelial carcinoma detected by transthoracic echocardiography: a case report

According to a recent review, cardiac metastasis from a malignant neoplasm is not
rare. In past autopsy studies, the incidences of cardiac metastasis were estimated
to range from 1.7 to 14 % in patients with cancer and from 0.7 to 3.5 % in the general
population 1]. By contrast, the incidence of primary cardiac malignant neoplasm ranged from only
0.001 to 0.28 % 2]. In addition, the incidence of cardiac metastasis is expected to increase because
of the improvement of prognosis for patients with cancer that is associated with advances
in cancer therapeutic strategies 1].

Bussani et al. reported a large series of autopsy cases in 2007 2]. They examined the cases of 18,751 in-hospital deceased patients, and they found
one or more malignant neoplasms in 7289 patients. They also found cardiac metastasis
in 662 of the patients (9.1 % of all), and the most common cancers among cardiac metastases
were lung cancer (39.2 % of cardiac metastasis cases from lung cancer), breast cancer
(10.0 %), mesothelioma (9.4 %) and lymphoma/leukemia (10.0 %). It was also shown that
mesothelioma, melanoma and lung cancer have a relatively high potential for cardiac
metastasis 2].

By contrast, cardiac metastasis from urothelial carcinoma is very rare. According
to the autopsy study from Bussani et al. only 12 of 307 patients with urothelial carcinoma had cardiac metastasis 2]. In fact, to the best of our knowledge, only a small number of cases of symptomatic
cardiac metastasis from urothelial carcinoma have been reported in the English literature.
The reason for the rarity of cardiac metastasis from urothelial carcinoma is unclear.
However, it may be due to the metastatic pathway of urothelial carcinoma. Malignant
tumors metastasize to the heart by four alternative pathways: direct extension, hematogenous
spread, lymphatic spread, and intracavitary extension from the inferior vena cava
3]. In epithelial malignancies, including urothelial carcinoma, distal metastasis occurred
mainly by the lymphatic pathway 3]. However, in the heart, lymphatic flow is directly from the endocardium to the epicardium,
and lymphatics drain from the heart to the mediastinum. It is therefore speculated
that tumor cells cannot easily reach the heart without lymphatic flow stagnating due
to tumor emboli 2]. This mechanism of the lymphatic system may play an important role in the rarity
of cardiac metastasis from urothelial carcinoma.

The prognosis of cardiac metastasis from urothelial carcinoma is poor. Hattori et al. showed in a review of 14 cases that most patients died shortly after the original
diagnosis or first visit 4]. Systemic chemotherapy or surgical resection of the tumor resulted in a prognosis
of relatively long survival in only a few patients 5]–8]. In our case, cardiac metastasis was detected by screening echocardiography for paroxysmal
atrial fibrillation before the patient had any complaint, and systemic chemotherapy
for urothelial carcinoma resulted in relatively long survival. Thus, early detection
of cardiac metastasis and prostatic recurrence of carcinoma may have been important
for the relatively long survival of our patient.

In addition, in our case, ECG showed characteristic abnormality (mild ST elevation
and T inversion in V1–3). The exact cause of this ECG abnormality is unknown, but
myocardial injury of the RV apex wall attributed to the metastatic tumor may have
resulted in the ECG abnormality. A similar ECG abnormality was reported by Na et al. in a case of mimicking ST-segment elevation in myocardial infarction 9]. This case suggested that new onset ECG abnormality might provide a clue for the
diagnosis of cardiac metastasis.