Teaching Case

A 71-year-old woman with a past medical history of Multiple Myeloma underwent CT for left-sided flank pain. The patient had previously received treatment for myeloma with an autologous stem cell transplant.  Blood results on the day were unremarkable.

CT pulmonary angiogram, abdomen and pelvis revealed extensive sclerotic vertebral body lesions and subtle sclerosis of the left lateral 6th rib (Figure 1a - 1b).  Additionally, a large 7.6 x 7.8 cm hypoattenuating lesion was noted in the right lobe of the liver (Figure 2).

MRI revealed the liver lesion to be generally T2 hyperintense with a stellate-like focus of higher T2 signal centrally (Figure 3a).  T1 signal was hypointense (Figure 3b). Contrast-enhanced sequences revealed brisk heterogeneous arterial enhancement with partial washout in the portal venous phase (Figure 3c – 3d).  The central hyperintense element retained contrast in the delayed phase images, likely indicating a necrotic focus,  differential for this included a central scar associated with focal nodular hyperplasia or fibrolamellar hepatocellular carcinoma. (Figure 3e). Diffusion-weighted sequences revealed very high DWI signal with corresponding low ADC values indicating diffusion restriction (Figure 4).  No further hepatic lesions were demonstrated.

The patient subsequently underwent an ultrasound guided liver biopsy to obtain a histological diagnosis. Histology revealed sheets of plasmacytoid cells without blastic features. CD138, CD56 and LCA were positive. CD117, CD20, AE 1-2 and neuroendocrine markers were negative. Overall, consistent with plasmacytoma.

Multiple myeloma is a haematological malignancy of plasma B cells affecting mainly men above 40 years old.  Myeloma can produce monoclonal proteins; replace bone marrow, cause hypercalcemia, cytopenia and renal failure. A precursor condition, monoclonal gammopathy of unknown significance (MGUS), is a clonal proliferation of plasma cells with production of paraprotein in the absence of symptomatic clinical manifestations of myeloma [1]. Solitary plasmacytoma is a malignant lesion consisting of plasma cells, without the production of paraprotein, but again without systemic features of myeloma [2].  The treatment of myeloma consists of options of a variety of systemic chemotherapy regimens and autologous stem cell transplantation in selected individuals.

Myeloma primarily affects the skeletal system, commonly manifesting as lucent bone lesions. Extra-osseous disease appears to be common at autopsy, affecting 64% of patients in one study where disease was found in the liver, spleen and lymph nodes.  The liver may be involved in up to 29% of cases [2, 3].  Radiologically evident extra-osseous disease is however not common, being found in 13% in one study. Extra-osseous disease common manifesting as soft tissue surrounding bone lesions, and less commonly affects the lymph nodes, liver and kidneys [4]. 

Involvement of the liver can manifest as diffuse infiltration or focal nodular lesions. Clinically, the patient may experience liver dysfunction,  an important differential in this scenario is hepatic amyloidosis secondary to the multiple myeloma itself [2].

Although predominantly hypoechoic at ultrasound, focal lesions can have a varying appearance, including targetoid, mixed or hyperechoic appearances. On CT, focal liver lesions are usually hypo-attenuating [2].

On MR imaging, lesions can be both T1 and T2 hyperintense, owing to their para-protein content (Kelekis et al. as cited by Tomasian et. al) [2]. Contrast enhancement can be minimal. FDG-PET imaging may reveal significant uptake within the lesion (Philips et al. 2012, as cited by Tomasian et. al) [2]. Owing to the nonspecific appearances that hepatic involvement can produce, lesions can be mistaken for metastatic lesions from more common solid tumours. A high index of suspicion is therefore necessary in a patient with a previous history of myeloma, with consideration for tissue diagnosis to confirm the diagnosis as needed [2].

Written informed patient consent for publication has been obtained.