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.
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.
Muscular manifestation of multiple myeloma.
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1. From the provided right shoulder X-ray (anteroposterior view of the shoulder joint), thickened soft tissue shadows are observed around the right shoulder joint, showing clear soft tissue swelling compared with the contralateral side. There are no obvious signs of pathological fracture in the proximal humerus; however, there may be slight osteopenia or changes in bone contour (e.g., irregular margins or reduced density).
2. On the MRI images in the transverse plane (T1-weighted, T2-weighted sequences, etc.), abnormal signal foci are seen within the deltoid, supraspinatus, and surrounding shoulder muscles. The lesions present as mass-like or diffuse infiltrating changes. Some areas show relatively high T2 signal and marked enhancement after contrast administration, suggesting an active lesion.
3. The lesion is generally ring-shaped or diffusely distributed, involving surrounding soft tissues. The boundaries are not well-defined, suggesting a possible tumor or infiltrative process. There is no significant sign of tear in the joint capsule or proximal tendons, but joint mobility may be affected by the mass effect or pain.
Based on the imaging findings and the patient’s history (previously diagnosed multiple myeloma, current right shoulder pain, fever, and skin erythema), the following diagnoses are considered:
1. Extramedullary Myeloma (multiple myeloma infiltration)
— The patient has a confirmed history of multiple myeloma. Currently, there is a significant mass and infiltrative changes in the shoulder muscles, with clinical signs of progressive symptoms. These findings support the possibility of extramedullary progression or infiltrative lesions of multiple myeloma.
2. Non-Hodgkin’s Lymphoma or Other Lymphatic Hematologic Malignancies
— Muscle masses or diffuse infiltration can be seen in certain lymphomas. However, considering the patient’s background of multiple myeloma, the likelihood of another lymphatic malignancy is relatively lower, though it cannot be completely excluded if there is suspicion of another lymphatic system tumor involving the muscles.
3. Soft Tissue Sarcoma (e.g., synovial sarcoma, rhabdomyosarcoma, etc.)
— Soft tissue tumors often present as irregular soft tissue masses. However, given the patient’s history of hematologic malignancy and the MRI enhancement pattern, the possibility of a primary soft tissue sarcoma is relatively low.
4. Infectious Lesion or Abscess
— The patient has low-grade fever and localized skin redness, so infection should be ruled out. However, intermittent low-grade fever and a known history of malignancy make tumor infiltration more likely. If in doubt, blood cultures or a biopsy could be performed to exclude infection.
Considering the patient is 58 years old with a known history of multiple myeloma, progressive right shoulder pain and swelling, imaging findings of diffuse infiltrative lesions in multiple shoulder muscles, as well as intermittent low-grade fever, the most likely diagnosis is: Extramedullary multiple myeloma (involving the right shoulder muscles).
If a more definitive confirmation is needed, a biopsy with pathological and immunophenotypic analysis (e.g., CD138 or other related markers) is recommended to verify the presence of plasmacytoma and reach a final diagnosis.
1. Treatment Strategy
• Systemic Treatment: Based on the initial treatment strategy for multiple myeloma. If there is evidence of extramedullary disease progression, consider intensified chemotherapy or combination with novel agents (e.g., proteasome inhibitors, immunomodulators), depending on the patient’s performance status and disease progression. Assess whether further stem cell transplantation or modification of maintenance therapy is needed.
• Local Radiotherapy: For significant localized pain or lesions impacting function, radiotherapy can be considered to control focal lesions, relieve pain, and improve shoulder joint mobility.
• Surgical Intervention: If the local tumor volume is large and affects joint stability or causes severe compression symptoms, consider debulking surgery or soft tissue reconstruction on the basis of chemotherapy or radiotherapy. Postoperative rehabilitation efforts and the patient’s overall condition should be carefully evaluated.
• Supportive Care: This includes nutritional support, infection prevention, and bone protection agents (e.g., bisphosphonates) to mitigate bone destruction and complications.
2. Rehabilitation/Exercise Prescription (FITT-VP Principle)
• F (Frequency): Initially, 2-3 times per week. Once pain is significantly alleviated and the condition stabilizes, the frequency may increase to 3-4 times per week.
• I (Intensity): Tailor intensity to the patient’s pain tolerance, muscle strength, and overall condition. Start with low-intensity stretching, joint mobilization, and light resistance exercises. Avoid heavy loads or fast-paced movements to protect weakened bone structures and reduce muscle strain.
• T (Time): Each rehabilitation session is recommended to last 20-30 minutes, which can be divided into intervals. For example, 10 minutes of warm-up followed by 10-20 minutes of joint mobility and assisted exercises.
• T (Type): Focus primarily on gentle shoulder muscle strengthening, stretching, and proprioception training. Utilize resistance bands or very light dumbbells as aids. Hydrotherapy or physical therapy modalities may also help relieve pain.
• V (Volume): Gradually increase exercise volume according to pain tolerance, avoiding sudden excessive loading. Each week, you may add 1-2 new exercises or increase repetitions as tolerated.
• P (Progression): As symptoms improve and strength increases, gradually intensify exercises and include more complex movements. Progress from passive movements to active movements, then to using supportive devices or resistance equipment. Monitor changes in pain, swelling, and fatigue to adjust the plan accordingly.
If severe pain, increased swelling, or systemic discomfort develops during training, stop immediately and seek medical evaluation. Given this patient’s vulnerable bone structure and the presence of infiltrative tumors, all exercises should be moderate and progressive, avoiding falls and high-impact activities.
Disclaimer:
This report is a reference-based analysis derived from the available imaging and patient history, and cannot replace an in-person consultation or professional medical advice. Actual treatment and rehabilitation plans should be determined by specialists based on the patient’s specific condition, laboratory results, and clinical assessment.
Muscular manifestation of multiple myeloma.
