A 71-year-old male patient, with a 12-year history of seropositive rheumatoid arthritis, presented with a one-month history of a painful swelling of the right shoulder accompanied by night sweats and weight loss.
A 71-year-old male, with a 12-year history of seropositive rheumatoid arthritis, presented with 1month history of a painful swelling of the right shoulder. He was treated using methotrexate [5 mg/wk]. Examination revealed a firm, tender swelling over the right shoulder. He had markedly raised inflammatory markers [ESR: 140 mm/hr and CRP: 270 mg/l] which raised the possibility of septic arthritis which was negative. Chest radiograph revealed destruction of the lateral third of the right clavicle, and an overlying soft tissue mass (Fig. 3). Magnetic resonance [MR] imaging showed a diffuse swelling of the supraspinatous muscle which appeared intermediate in signal intensity on T1-and T2-weighted sequences and demonstrated diffuse high signal changes on STIR sequences (Fig. 1). Following administration of intravenous gadolinium, the supraspinatous muscle and the overlying soft tissues demonstrated a peripheral enhancement with central areas of low signal intensities (Fig. 2). The peripheral enhancement may well be secondary to liquifaction or high interstitial pressure. The marrow signal of the glenoid and the humeral head appeared normal. Trucut biopsy confirmed the presence of a high grade B-cell lymphoma. CT chest and abdomen showed the involvement of right pectoralis major, serratus anterior and left levator scapulae and supraspinatous muscle, but no distant lymphadenopathy or organomegaly (Fig. 4a, b). Methotrexate was discontinued and chemotherapy [CHOP-cyclophosphamide, doxorubicin, vincristine and prednisolone] started, following which the mass reduced in size. With diffuse involvement of multiple musculatures, this was likely to be a primary lymphoma of the muscle with the secondary involvement of the bone.
Although 20%–30% of non-Hodgkin lymphomas [NHL] manifest extranodally, muscle involvement occurs in only 1%–2% of all cases of lymphomas (4). Skeletal muscle involvement may be due to a systemic spread or the contiguous extension of the disease from the bone (4). Rarely, lymphomas can occur primarily in skeletal muscle (4). Due to the rarity of this condition, collective information is sparse, but most cases are of large or polymorphous, B-cell phenotype (4). The most frequently affected sites are the lower extremities. Reports of malignancy occurring in rheumatoid arthritis patients on undergoing methotrexate treatment continue to appear in the literature (2). The likely pathogenic mechanism includes altered T-cell function in rheumatoid arthritis; methotrexate induced T-cell dysfunction or occurrence by chance (2). Certain reports suggest that tumours regress after discontinuing methotrexate therapy (2), although other reports refute this. Despite a retrospective study done by Moder et al., which did not support a relationship between methotrexate use and the development of malignancy (1), physicians caring for affected patients should include heightened surveillance for lymphomas (2) in their treatment schedule. Plain radiographs in most cases of skeletal muscle lymphomas are seen to be normal, or may reveal a soft tissue mass with variable bone destruction. On ultrasound scanning, lesions may appear as non-specific masses (5), without a fluid level. On CT scans, the muscle involved is usually enlarged and appears iso or hypodense with varying degrees of enhancement (4,5). On MR imaging, lymphomas appear iso or minimally hyperintense compared to muscle on T1-W images and enhanced and hyperintense on T2-W, proton density and fat suppression sequences. Infiltration of the subcutaneous fat is a striking feature in the majority of cases on CT and MR (4, 5). A Hodgkin’s lymphoma tends to be brighter when compared to NHL on MR imaging (3). The reason for this is far from clear but could be explained as being due to oedema or inflammation (3). Adjacent subcutaneous stranding or extension is also highly suggestive of the presence of NHL (5). Bone and gallium scans are useful for excluding systemic disease, and for follow-up of recurrent disease. The differential diagnosis of a soft tissue mass is varied and include tumors like liposarcomas, fibrous histiocytomas and sarcomas. Although, it is possible to make a radiographic diagnosis of the type of tumour, it is often difficult to accomplish. An intramuscular abscess can sometimes simulate malignancy (4), as was initially suspected in this case. It is often difficult to distinguish sarcomas from metastatic carcinomas based on imaging (4). A skeletal muscle lymphoma should be considered in the differential diagnosis for soft tissue masses developing in patients with rheumatoid arthritis on undergoing methotrexate therapy. It is important to consider the possibility of lymphomas being present, as special stains are often needed to differentiate the tumours by histology and to plan further management.
Lymphoma of skeletal muscle associated with long-term methotrexate therapy.
Based on the provided right shoulder MRI, chest X-ray, and CT scan, the following observations can be noted:
The combined imaging indicates a mass-like lesion within the right shoulder soft tissues, with partial involvement of the surrounding fat and muscle tissue. Downstream muscle edema is clearly visible.
Considering the patient’s age (71 years), long-term rheumatoid arthritis (12 years), methotrexate (MTX) treatment, and recent symptoms of night sweats and weight loss, the following diagnoses should be prominently considered:
Based on the patient’s history (long-term rheumatoid arthritis on methotrexate), clinical symptoms (night sweats, weight loss, painful mass), and imaging findings (soft tissue mass within the right shoulder musculature with high T2 signal and surrounding fat infiltration),
the most likely diagnosis is non-Hodgkin lymphoma (NHL) of the skeletal muscle.
Further confirmation can be achieved through nuclear medicine examinations (bone scan, PET/CT) or biopsy (histopathology and immunohistochemistry).
Once the diagnosis of “musculoskeletal non-Hodgkin lymphoma” is established, the treatment plan is typically determined by a multidisciplinary team including hematology, oncology, and surgery. Possible approaches include:
Rehabilitation & Exercise Prescription (FITT-VP Principle):
If the patient has fragile bones or reduced cardiopulmonary function, a comprehensive evaluation with rehabilitation specialists is recommended to ensure safety and a gradual progression of activity.
Disclaimer: This report is a reference analysis based on available data and cannot replace a face-to-face consultation or professional medical advice tailored to the individual. In case of any abnormalities or changes in condition, please seek prompt medical attention.
Lymphoma of skeletal muscle associated with long-term methotrexate therapy.
