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MR IMAGING OF HEPATIC PLASMACYTOMA: A CASE REPORT BA D. NGUYEN, MD, NILIMA DASH, AND ANTHONY R. LUPETIN, MD

A case of kappa light chain multiple myeloma with space-occupying hepatic plasmacytoma is presented. Magnetic resonance (MR) imaging shows an eccentric multiple-layer pattern of the liver mass and suggests malignancy. Differential diagnosis concerning the MR appearance of this rare hepatic tumor is discussed. KEYWORDS: Multiple myeloma; Hepatic plasmacytoma; Magnetic resonance imaging INTRODUCTION

Plasma cell infiltration of the liver has been noted in up to 40% of patients with multiple myeloma (MM) in a postmortem series (1,2,3). However, space-occupying hepatic plasmacytoma is rarely encountered in living myelomatous patients (4). It can mimic metastatic disease or other primary neoplasms because the reported sonographic and computed tomographic features are nonspecific (5). The magnetic resonance (MR) appearance of hepatic plasmacytoma in a patient with kappa light chain multiple myeloma is described. CASE REPORT

A sixty-seven-year-old black man presented with a 4-month history of a 20 lb weight loss, increasing fatigue, anemia, renal failure, and recent onset of From the Department of Diagnostic Radiology, Allegheny General Hospital and The Medical College of Pennsylvania, Pittsburgh, Pennsylvania. Address reprint requests to: Nilima Dash, MD, Department of Diagnostic Radiology, Allegheny General Hospital, 320 East North Avenue, Pittsburgh, PA 15212-9986. Received July 1991; revised August 1991. 0 1992 by Elsevier Science Publishing Co., Inc. 655 Avenue of the Americas, 0899-7071/92/$5.00

New York, NY 10010

MD,

slurred speech and lethargy. During a previous hospitalization at another institution, he was found to have a left hepatic tumor. The computed tomography (CT) scan of his head was normal. On admission to our hospital, the patient complained of right upper quadrant and back pain. The physical examination revealed a slightly lethargic patient who was still oriented to place and person, with no focal neurologic deficit. There was no abdominal organomegaly or mass. The lab work showed a serum calcium level of 14.4 mg/dl, a blood urea nitrogen (BUN) level of 69 mg/dl, and a serum creatinine level of 3.8 mg/dl. There was pancytopenia with a normochromic and normocytic anemia. The hemoglobin level and the hematocrit were 10.3 gm/dl and 30.8% respectively. All liver function tests were within normal limits. The assessment of the liver mass was carried out by ultrasound (US), CT, and MR. The sonogram mass occushowed an 8 cm x 9 cm heterogeneous pying the entire lateral segment of the left liver lobe. This mass had three eccentric layers: an outer hypoechoic area that surrounded a hyperechoic rim, and a near fluid-echogenicity inner core (Figure 1). The computed tomography was performed without contrast enhancement because of the patient’s renal failure. CT failed to furnish any additional information (Figure 2). The MR was performed at 1.0 T utilizing Tl- and T&weighted spin echo pulse sequences with TRITE of 600/15 ms, 2000/60 ms, and 2000/120 ms, respectively. A breath-hold gradient echo sequence was also performed with a flip angle of 40” and TR/TE of 50110 ms. MR confirmed the three-layer pattern of the mass (Figure 3). Tl-weighted images showed a hypointense outer component, a hyperintense rim, and an eccentric isointense/hyperintense center. T2-weighted scans demonstrated a hyperintense outer layer, a hypointense rim, and a hyperintense inner core.

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FIGURE 1. Ultrasound of the left hepatic lobe in the longitudinal plane shows a space-occupying lesion with a threelayer pattern: hypoechoic outer layer (arrowheads), hyperechoic thin middle component (arrows), and hypoechoic center.

A peripheral blood smear was positive for plasma cells and rouleau formation. The serum immunoelectrophoresis demonstrated no monoclonal protein, but the urine immunofixation was positive for kappa monoclonal light chain. The bone marrow biopsy revealed large sheets of plasma cells replacing the B FIGURE 2. Unenhanced

CT scan of the liver demonstrates a mass involving the entire lateral segment of the left lobe (arrowheads). The three layer pattern is not seen. There is a right rib lesion (arrow).

FIGURE 3. (A) Axial Tl-weighted

section (TRITE = 6001 15 ms) shows the eccentric three-layer tumor in the lateral segment of the left liver lobe. The irregular and poorly circumscribed outer layer is hypointense (arrowheads). The thin median layer is hyperintense (arrows) and the center is isointense relative to the hepatic parenchyma. (B) Axial T&weighted scan (TR/TE = 2000/120 ms) shows the mass with a hyperintense peritumoral edema (arrowheads), a hypointense middle layer (arrows), and a hyperintense center.

normal osseous architecture with an average cellularity of 70%. There was no evidence of metastatic carcinoma or granulomatous inflammation in the biopsy specimen. The US-guided liver biopsy revealed the presence of atypical plasma cells consistent with hepatic plasmacytoma. Workup for back pain demonstrated osteopenia, wedging of the thoracic and lumbar spine, along with rib lesions observed on CT and MR. A diagnosis of

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kappa light chain multiple myeloma with liver plasmacytoma and bone lesions was made. He received a cycle of Alkeran@ and Prednisone along with 3000 grays of radiation over the vertebral lesions. The patient did well under these therapies. His mental status was markedly improved following IV hydration and Lasix.@ He was discharged with improved renal function. DISCUSSION

Hepatic involvement as a space-occupying mass in plasma dyscrasias is rare. &tmay be an isolated entity of extramedullary plasmacytoma (EMP) or an integrated part of the multiple manifestations of myelomatosis with anemia, renal failure, and osseous lesions (1, 2, 3, 6). EMP involves predominantly the nasopharynx and upper respiratory tract (6, 7). It can also affect the gastrointestinal tract and the liver (4, 8). Only one report has demonstrated the sonographic and CT features of hepatic EMP (5). The diagnosis of EMP requires the absence of bone marrow plasmacytosis, a normal bone survey, and plasma-cell infiltration only at the site of EMP (7). Our reported case is a confirmed kappa light chain multiple myeloma with liver plasmacytoma. Autopsy series demonstrated up to 40% of MM patients as having hepatic plasma cell infiltration (1,2,3), but rare are reports of tumoral plasmacytoma in living patients (4). The liver’s reticuloendothelial system represents a frequent site of plasma cell spread in MM (1, 2, 3). The hepatic lesions are secondary to diffuse, nodular, sinusoidal, or portal plasma-cell infiltration with fatty changes mimicking metastatic disease or primary liver tumors. Hepatic plasmacytoma has been reported to be hypoechoic on ultrasound, homogeneously hypodense with heterogeneously progressive enhancement on CT (5). These features are nonspecific. MR has been demonstrated to accurately show tumors of the liver and thin tissue characterization (9, 10, 11). Tl- and TZweighted images show good anatomic resolution and help define criteria of malignancy of liver masses (11). On MR, our case has an eccentric three-layer pattern, which could suggest the combined “target” and “halo” features (11) or a multiple “ringed” pattern (12) previously described in the literature. The outer layer, with hypointense Tl and hyperintense T2 signals, is consistent with a zone of peritumoral edema. The thin, median rim, hyperintense on Tl-weighted images and hypointense on T2-weighted scans, suggests a fatty component. The core, with isointense/

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hyperintense Tl signal and hyperintense T2 signal probably represents a necrotic and hemorrhagic center. US, CT, and MR correlation showed no tumoral calcification and no vascular invasion. The multiple layer appearance with irregular and poorly circumscribed margins of this mass suggests malignant liver involvement (9, 10). Metastatic disease and melanoma may frequently appear similar with the presence of peritumoral edema and necrotic or hemorrhagic center. The fatty median rim is, however, atypical for metastasis. This rim of fatty degeneration might raise the diagnosis of hepatic cell carcinoma (HCC) even though typical HCC frequently demonstrates vascular invasion and hypointense Tl signal fibrotic pseudocapsule (9). Carcinosarcoma, a very rare liver neoplasm, could also have similar MR features. Hemangioma would be atypical due to the presence of a isointense/hyperintense center on Tlweighted images. The absence of hepatomegaly, the absence of liver function disturbance, the rarity of macroscopic liver plasmacytoma and the lack of defined MR features did not contribute to the identification of this lesion. The liver mass present in our case is an incidental finding which was thought to be either metastatic disease, atypical HCC, or atypical hemangioma. Myelomatous manifestations (1, 6) of the patient (normochromic and normocytic anemia, elevated serum calcium, renal failure, bone lesions, and especially the presence of kappa light chain) should have made hepatic plasmacytoma a possibility in the differential diagnosis. Biopsy was necessary to reach to the final diagnosis.

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