1. Imaging Findings

Based on the provided CT and MRI images of the left shoulder, a noticeable soft tissue mass is observed near the shoulder joint:

• On the CT images, the lesion appears as a soft tissue mass similar in density to muscle, with relatively clear boundaries and relatively homogeneous internal density.
• Some images suggest a slight involvement or destruction of adjacent bone (localized bone erosion or thinning of the cortex can be seen).
• On MRI, the lesion typically shows iso- or slightly low signal on T1-weighted images (comparable to muscle signal), and mildly high signal on T2-weighted images compared to muscle. This indicates a contrast in signal intensity relative to surrounding muscles.
• After contrast enhancement, the lesion mostly demonstrates homogeneous enhancement, but occasional ring-like enhancement may also be seen, which can mimic abscesses or other solid tumors.

2. Potential Diagnoses

Based on the patient’s medical history (chronic myelogenous leukemia in accelerated phase/myeloid blast crisis) and imaging characteristics, the following differential diagnoses are considered:

1. Hematoma: If the patient had trauma or coagulation disorders, a soft tissue mass could represent a hemorrhagic lesion; however, in this case, there is no significant history of trauma, and the feature of uniform enhancement is atypical for a simple hematoma.
2. Localized infection (e.g., abscess): Immunocompromised patients are at higher risk. However, abscesses usually show prominent rim enhancement after contrast administration, along with local inflammatory or systemic infection signs.
3. Sarcomatous lesion (such as sarcoma or sarcomatous metastases): Infiltration of various tissues involving bone and soft tissues can present as masses. However, given the background of CML, myeloid sarcoma (granulocytic sarcoma) should be considered first.
4. Granulocytic sarcoma (Chloroma): Also known as myeloid sarcoma, it is a tumor formed by extramedullary infiltration of precursor granulocytes and can be seen in acute or blast-phase CML and other myeloid leukemias. In imaging, it often appears as a homogeneous soft tissue density/signal, frequently associated with bone destruction or infiltration.

3. Final Diagnosis

Considering the patient’s history of CML in blast crisis, imaging findings, and pathological examination, the most likely diagnosis is:

Granulocytic Sarcoma (Chloroma, also known as myeloid sarcoma).

Since this condition represents an extramedullary manifestation of CML or AML, it requires close attention and prompt intervention. If doubt remains regarding the nature of the lesion, further pathological biopsy and immunohistochemical staining (e.g., MPO, CD68, CD117) can confirm the diagnosis.

4. Treatment Plan and Rehabilitation

4.1 Treatment Strategy

• Chemotherapy and targeted therapy: For patients in the accelerated or blast phase of CML, comprehensive chemotherapy and/or targeted therapy (e.g., tyrosine kinase inhibitors) should be arranged by the Hematology Department.
• Local radiotherapy: Granulocytic sarcoma is sensitive to radiation. Local radiotherapy can effectively control the size of the soft tissue lesion and alleviate local symptoms.
• Surgical intervention: If the tumor is large, causes joint dysfunction, or severe pain unresponsive to chemo or radiotherapy, surgical resection may be considered. Generally, surgical decisions should be made in conjunction with systemic hematologic treatment considerations.

4.2 Rehabilitation / Exercise Prescription Recommendations

1. Early rehabilitation: During the active phase of the lesion or treatment, the primary goals are to protect joint function and prevent disuse muscle atrophy. Possible activities include:
   • Low-intensity joint exercises, such as gentle eccentric/concentric movements of the shoulder joint.
   • Passive or assisted active movements to maintain range of motion.
   • Avoid excessive loading or repetitive impact activities to prevent further bone or soft tissue damage.
2. Intermediate rehabilitation: Once active treatment is underway and symptoms improve, progressively increase strength and endurance training:
   • Use moderate or low resistance shoulder strengthening exercises (e.g., elastic bands or light dumbbells), with slow, controlled movements.
   • Incorporate aerobic activities (e.g., walking or stationary cycling), for 15-20 minutes per session, 3-5 times a week, gradually increasing volume.
3. Late rehabilitation and exercise progression (FITT-VP principle):
   • Frequency (F): 3-5 times per week.
   • Intensity (I): Gradually increase based on the patient’s subjective perception (e.g., Borg scale) and trunk stability, maintaining a moderate level of exertion.
   • Time (T): 20-40 minutes per session, with the option of splitting sessions to avoid excessive fatigue.
   • Type (T): Combine resistance training (rotator cuff and scapular stabilizers) with endurance exercise (e.g., cycling, walking).
   • Progression (VP): Gradually increase resistance or extend duration every 2-4 weeks.

   During this period, closely monitor blood counts and bone status. If significant bone erosion or poor general condition is present, reduce training volume or pause exercise as needed.

Safety Considerations: Given the background of myeloid leukemia and potential bone involvement, be especially vigilant about fracture risk and local pain. If severe pain or discomfort occurs during exercise, reduce the load or stop, and seek medical evaluation promptly.

Disclaimer: This report is provided for reference only and does not substitute an in-person consultation or professional medical advice. For specific treatment plans, please consult Hematology, Orthopedics, and other relevant specialists.