CASE 14993 Published on 15.09.2017

An unusual shoulder lump


Musculoskeletal system

Case Type

Clinical Cases


Nichelli L., Ciliberti M., Torricelli P.

Azienda Ospedaliero-Universitaria di Modena - Policlinico, Dipartimento di Diagnostica per Immagini; Largo del Pozzo, 71, 41125, Modena (MO), Italy.

58 years, male

Area of Interest Haematologic, Musculoskeletal soft tissue ; Imaging Technique MR, Ultrasound
Clinical History
A 58-year-old white man with a 7-year history of multiple myeloma complained of painful right shoulder swelling gradually increasing over the last month. The patient reported intermittent low-grade fever and occasional overlying skin erythema. Glenohumeral joint movements were reduced and asymmetry in comparison with the left shoulder was visible.
Imaging Findings
A first shoulder X-ray was normal. Ultrasound examination suspected a full-thickness rotator cuff tear and a large fluid collection containing hyperechoic material.

After one month a second shoulder radiography highlighted a marked soft tissue thickening (Fig. 1). An MRI was planned and showed a voluminous diffuse shoulder musculature enlargement due to the presence of a large, mass-forming tissue, with indistinct boundaries, exceeding epimysium and involving deltoid, biceps brachii, pectoralis major, serratus anterior, subscapularis, supraspinatus and infraspinatus muscle. The signal of the lesion was isointense relative to unaffected musculature on T1-weighted images and heterogeneously hyperintense on T2-weighted images (Fig. 2). The administration of intravenous gadolinium revealed marked, diffuse homogeneous enhancement (Fig. 3). Reticulation of the subcutaneous fat, small central area of colliquative necrosis and multiple enlarged axillary lymph nodes were also seen.

Ultrasound-guided percutaneous biopsy (Fig. 4) was performed and extramedullary involvement of multiple myeloma was diagnosed.
Multiple myeloma (MM) is a clonal plasma cell malignancy usually restricted to bone marrow. It’s the second most common haematology cancer (10%) after non-Hodgkin lymphomas, with a slightly male predominance and a median age at the time of diagnosis of 65 years [1].

Extramedullary myeloma (EM) is an unusual type of MM, characterised by extraskeletal clonal plasma cell infiltrates [2]. It may be present either at the time of initial diagnosis (primary EM) or it may develop during disease relapse (secondary EM) [3]. Some studies have suspected an increase of secondary EM after autologous and allogenic stem-cell transplantation or during high-dose therapy, but Varettoni et al. [4] have shown no association with prior exposure to these drugs and have correlated the increase of EM relapses to prolongation of patients’ survival.

Natural history of EM has not been completely understood. Bladé et al. depicted two possible mechanisms of extramedullary spread, one arising from contiguous extension of skeletal lesions, and another one involving haematogenous dissemination of cells with decreased adhesion molecule expression, resulting in a bone marrow escape [5]. Usmani et al. identified single gene mutations associated with EM disease [6].
Unfortunately, EM is considered a highly aggressive disease and is associated with shorter overall and progression-free survival even in the era of novel agents [4, 6].

Muscle is not a common site of EM disease, while liver, skin, kidney, pleura and lymph nodes are more frequently involved [3, 7]. To the best of our knowledge this is the first case that describes shoulder multiple musculature involvement of MM.

Muscular manifestation of extranodal lymphomas has been more often reported and seems to share similar clinical, laboratory and MRI features with myeloma muscular involvement. Surov et al. identified two different MRI types of muscular manifestations in malignant immunoproliferative diseases: a (1) diffuse mass-forming pattern, clinically associated with local pain, and a (2) focal intramuscular mass pattern, clinically silent [8]. They concluded describing the first pattern as typical of NHL while the latter as a characteristic of myelomas. Instead, in our patient muscle involvement clearly resembled the lymphoma pattern, and our MRI images are comparable to Chandramohan M. et al. lymphoma case report [9].

In conclusion, the atypical plasma cells muscle involvement shown in this case report strengthens the idea that MM should not be considered only as a single marrow-restricted disease but also as a complex collection of several distinct plasma cell malignancies.
Differential Diagnosis List
Muscular manifestation of multiple myeloma.
Inflammatory - infectious disease (muscle abscess pyomyositis)
Pleomorphic undifferentiated sarcoma
Final Diagnosis
Muscular manifestation of multiple myeloma.
Case information
DOI: 10.1594/EURORAD/CASE.14993
ISSN: 1563-4086