Introduction

Leiomyosarcoma is a soft tissue tumor arising from smooth muscle cells with significant metastatic potential and poor prognosis, accounting for approximately 5–7% of soft tissue sarcoma cases [1]. Leiomyosarcoma predominantly affects women in their sixth decade of life [2]. Cases involving vascular structures represent only 2% of the cases and are primarily localized to the inferior vena cava (IVC) [3, 4]. Vascular leiomyosarcoma has been reported to affect minor vessels. However, only a few cases of portal vein (PV) leiomyosarcoma are reported in the literature [5,6,7,8,9,10,11,12,13,14,15,16,17]. Herein, we report a case of primary leiomyosarcoma originating from the PV, which presented as a pancreatic head tumor with protrusion into the PV.

Case presentation

A 59-year-old woman visited our hospital because of an elevated amylase level during a medical checkup. She had no subjective symptoms or abdominal masses. Blood tests showed the following vitals—white blood cell count, 5000/μL; hemoglobin level, 12.9 g/dL; aspartate transaminase level, 21 U/L; alanine transaminase level, 17 U/L; γ-glutamyl transpeptidase level, 26 U/L; amylase level, 210 U/L (normal range: 54– 168 U/L); carcinoembryonic antigen level, 1.1 ng/mL; and carbohydrate antigen 19–9 level, 2.5 U/mL. There were no abnormalities, except for an elevated amylase level.

Dynamic computed tomography showed a 35 × 30-mm well-demarcated lobulated mass in the pancreatic head, which had iso-, low-, low-, low- density in plain, arterial, portal, and equilibrium phase, respectively. The tumor was adjacent to the right wall of the PV and the superior mesenteric vein (SMV) and protruded into the PV without calcification or fatty component (Fig. 1). There was no dilatation of the main pancreatic or common bile ducts. Extracorporeal ultrasonography showed a 35 × 29-mm hypoechoic mass compressing the SMV in the pancreatic head (Fig. 2). Endoscopic ultrasonography (EUS) showed a well-defined nodular heterogeneous hypoechoic mass in the pancreatic head. The tumor expanded outside of the pancreas. Contrast-enhanced EUS using Sonazoid showed early staining with a partially poor enhancement in one area (Fig. 3). The T1-weighted image of magnetic resonance imaging (MRI) showed that the tumor had a signal almost equal to that of the muscle, while the T2-weighted image showed the tumor was mildly higher in signal than the muscle. MRI could not identify any difference in septa or internal properties. Magnetic resonance cholangiopancreatography (MRCP) did not show stenosis or dilatation of the main pancreatic duct or common bile duct (Fig. 4). Fluoro-deoxyglucose-positron emission tomography-computed tomography (FDG-PET-CT) showed hyper-accumulation of FDG in the pancreatic head with a SUVmax of 6.52 (Fig. 5). There was no abnormal FDG hyper-accumulation in other organs. Our preoperative differential diagnosis included gastrointestinal stromal tumor, neuroendocrine neoplasm, solid pseudopapillary neoplasm, acinar cell carcinoma, and anaplastic ductal carcinoma based on the imaging characteristics. Endoscopic ultrasound-fine-needle aspiration was not performed because of the necessity of pancreatoduodenectomy (PD). Subtotal stomach-preserving PD was performed with PV resection. The SMV was resected annularly 2 cm in length and anastomosed. The splenic vein was preserved (Fig. 6). The duration of surgery was 7 h, and the total blood loss was 360 mL.

Fig. 1
figure 1

Dynamic computed tomography images show a well-demarcated lobulated hypodense mass 35 mm in size in the pancreatic head (arrowhead). The tumor was adjacent to the superior mesenteric vein (SMV) and protruded into the portal vein (arrow). The tumor was mildly contrasted from the arterial phase to the equilibrium phase and is heterogeneously contrasted, with iso-, low-, low-, low- density in plain, arterial, portal, and equilibrium phase, respectively. a plain, b arterial, c portal, and d equilibrium phase

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Fig. 2
figure 2

Extracorporeal ultrasonography showing a hypoechoic mass of 35 × 29 mm in the pancreatic head compressing the superior mesenteric vein (SMV, arrowhead)

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Fig. 3
figure 3

a B-mode endoscopic ultrasonography (EUS) showing a well-defined nodular heterogeneous hypoechoic mass. b Contrast-enhanced EUS using Sonazoid showing early staining with a partially unenhanced area. c Location of the tumor (T), common bile duct (arrow), and main pancreatic duct (arrowhead)

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Fig. 4
figure 4

T1 weighted image (a) of magnetic resonance imaging shows that the tumor signal is almost equal to the muscle signal, while T2 weighted image (b) shows that the tumor is mildly higher in signal intensity than the muscle. Magnetic resonance cholangiopancreatography (c) showed neither stenosis nor dilatation of the main pancreatic duct and common bile duct

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Fig. 5
figure 5

Fluorodeoxyglucose-positron emission tomography-computed tomography (FDG-PET-CT) showing hyper-accumulation of FDG in the pancreatic head (SUVmax: 6.52) (arrowhead)

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Fig. 6
figure 6

a Intraoperative findings show a tumor (green arrowhead) in the pancreatic head and adjacent to the right wall of the superior mesenteric vein (SMV) (yellow arrow). b The SMV was resected annularly 2 cm in length and anastomosed (blue arrow). SMA: superior mesenteric artery (orange arrowhead)

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Macroscopic findings of the cut surface of the fixed resected specimen showed a white solid multinodular tumor protruding into the PV lumen on the right side of the PV (Fig. 7). Histopathologically, the tumor was composed of a palisade arrangement of spindle-shaped cells with nuclei of unequal size, cellular atypia, and eight mitoses in 10 high-magnification views (Fig. 8). Immunohistochemistry showed positive calponin, desmin, and α-SMA, and a 20% Ki-67 index (Fig. 9). In contrast, tests for CD34, c-Kit, and S-100 were negative. Elastica-Goldner staining showed well preserved PV elastic plate (Fig. 10). Considering the tumor location and protrusion into the PV lumen, the tumor was presumed to have originated from the connective tissue of the outer layer of the PV. The histopathological diagnosis was PV leiomyosarcoma invading the pancreatic head. The surgical margin was negative for leiomyosarcoma.

Fig. 7
figure 7

a Macroscopic findings of the resected specimen. b Cut surface of the resected specimen (indicated by a horizontal line in Fig. 7 [a]) showing a white solid multinodular tumor protruding into the portal vein (PV)

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Fig. 8
figure 8

Histopathological findings show a multinodular tumor composed of a palisade arrangement of spindle-shaped cells with nuclei of unequal size, cellular atypia, and 8 mitoses in 10 high-magnification views. a Loupe image, b Hematoxylin and eosin (HE), × 200, c HE, × 400

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Fig. 9
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Immunohistochemistry shows positive calponin (a), desmin (b), α-SMA (c), and 20% of the Ki-67 index (d)

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Fig. 10
figure 10

Histopathological image of the tumor around the SMV (a). HE, × 40. b Elastica-Goldner staining showing preservation of the lamina elastica of the portal vein (PV)

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Because of the soft pancreas and undilated main pancreatic duct, she developed a refractory grade C pancreatic fistula (International Study Group grading system) [18]. Fistulo-jejunal anastomosis was performed on the 145th postoperative day. The patient was discharged from our hospital 171 days after the first surgery. Thirty-eight months after the first surgery, CT showed an irregular, low-density lesion around the SMV (Fig. 11), indicating local recurrence. Considering the difficulty of surgical resection, radiation therapy (50.4 Gy) was administered, and the patient has been alive for the last 46 months after the surgery with partial response to radiation therapy.

Fig. 11
figure 11

At 38 months after the first surgery, computed tomography findings showed an irregular, low, dense lesion (arrowheads) around the SMV, indicating local recurrence

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Discussion

Leiomyosarcoma is a relatively rare mesenchymal tumor originating from the smooth muscle. Most leiomyosarcomas are found in the uterus, retroperitoneum, mesentery, and omentum (40%–45%); leiomyosarcomas originating from the vascular structures are rare (2%) [19, 20]. Leiomyosarcomas of venous origin are five times more common than those of arterial origin, and leiomyosarcomas of the IVC account for approximately 50% of primary venous leiomyosarcomas [21, 22].

Because the preoperative imaging characteristics, in this case, suggested a well-demarcated solid tumor with partial degeneration, our preoperative differential diagnosis included gastrointestinal stromal tumor, neuroendocrine neoplasm, solid pseudopapillary neoplasm, acinar cell carcinoma, and anaplastic ductal carcinoma, retrospectively. However, a well-demarcated tumor with expansive growth, protrusion into the PV lumen, as well as neither stenosis nor dilatation of the main pancreatic duct and common bile duct despite a large tumor in the pancreas head can indicate a giant leiomyosarcoma of the PV. Because the tumor was diagnosed before the development of portal hypertension and collateral blood vessels, standard PD with PV resection was performed safely.

Our extensive search for the reports of leiomyosarcoma originating PV (using the search terms ‘Leiomyosarcoma’ and ‘Portal vein’ in the PubMed from 1950 to 2021, and Japana Centra Revuo Medicina from 1977 to 2021) found only 13 reports of surgically resected leiomyosarcoma of PV origin in English and Japanese literature, including our case (Table 1) [6,7,8,9,10,11,12,13,14,15,16,17]. Among these reports, the median age of patients was 62 years (range: 42–78 years), and the sex was predominantly female (69%). The most frequent symptom was upper abdominal pain. The most frequent locations were the pancreatic head and porta hepatis, followed by liver and mesentery. The growth pattern of PV leiomyosarcoma can be divided into three types: intraportal with tumor plugs, extraportal growth, and combined type [11]. The intraportal, extraportal, and combined type growth was observed in 2, 2, and 5 cases, respectively. In the intraportal and combined types, portal hypertension with the development of collateral blood vessels can occur due to PV obstruction, making the resection challenging [7, 12, 14, 16]. The median tumor size was 5.9 cm (range: 3–30 cm) among all the cases. The most frequent CT findings were well-demarcated, enhanced, heterogeneous tumor. There was no specific MRI finding among the studies. Preoperative biopsy, including endoscopic ultrasound-guided fine-needle aspiration, was performed in 6 cases, which led to the preoperative diagnosis of leiomyosarcoma in 5 cases. The most frequent surgical procedure was PD with PV resection followed by hepatectomy with PV resection. Recurrence was mostly local, although follow-up periods were limited (median: 20 months).

Table 1 Thirteen cases of surgically resected portal vein leiomyosarcoma were reported in English and Japanese literatures (1990 ~ 2021)
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PV leiomyosarcoma should be considered as a differential diagnosis for pancreatic head tumors with protrusion into the PV. Precise macroscopic and histopathological examination, including immunohistochemistry, can help determine the definitive diagnosis and origin of leiomyosarcoma.