Medical Imaging Analysis Report

I. Imaging Findings

Based on the provided MRI and ultrasound images, a soft tissue mass-like lesion is observed in the left popliteal fossa. The lesion appears relatively well-defined in shape with partially clear borders. The internal signal characteristics are as follows:

• MRI T1-weighted imaging (T1WI): The lesion demonstrates isointensity to slightly high signal intensity.
• MRI T2-weighted imaging (T2WI) and STIR sequence: Inhomogeneous internal signals are noted, with relatively high-signal areas and relatively low-signal bands; it is inferred that the high-signal areas may correspond to regions with abundant cellular components, while the low-signal areas may correspond to collagen fiber proliferation.
• Ultrasound findings: A hypoechoic mass with relatively clear boundaries is noted, showing a fusiform shape and heterogeneous internal echoes.
• Contrast-enhanced imaging: The lesion exhibits a certain degree of enhancement, relatively uniform in pattern, with collagen-predominant regions showing slightly delayed enhancement.
• Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC): The lesion shows a relatively low diffusion coefficient, similar to some malignant tumors or lesions with high cellular density. However, when considering clinical and histological data, a benign yet locally aggressive fibromatous lesion can be suspected.

The lesion is located in the deep soft tissue of the popliteal fossa, adjacent to the joint capsule and tendons. No obvious bone destruction is noted; however, arthroscopy or further examination is recommended to exclude any involvement of the articular surface. Meanwhile, the lesion is in proximity to the major local blood vessels, though no clear vascular encasement or distortion is observed; preoperative evaluation should be conducted in collaboration with surgical and vascular teams.

II. Possible Diagnoses

Based on the patient’s age, gender, clinical symptoms, and imaging findings, the following possibilities are considered:

1. Aggressive fibromatosis (Desmoid tumor)
   Rationale: Common in young to middle-aged females, characterized by locally invasive growth. MRI findings often include isointense or slightly high T1 signal, high T2 signal, and heterogeneous enhancement, with a propensity for local recurrence. Clinical presentation typically includes pain or a palpable swelling.
2. Other soft tissue tumors in the popliteal region (e.g., liposarcoma, leiomyosarcoma, etc.)
   Rationale: Soft tissue tumors can occur in or around the knee or popliteal fossa. However, malignant tumors typically show more aggressive imaging features, including poorly defined margins and involvement of muscles or fascial layers. While a differential diagnosis consideration, clinical and histopathological correlation is critical.
3. Popliteal cyst (Baker’s cyst)
   Rationale: Most common in the posterior aspect of the knee, generally presenting as a fluid-filled outpouching of the joint capsule. On MRI, it usually displays fluid characteristics without significant enhancement. Clinically, there may be a noticeable fluid wave. Such findings differ from the fibrous components observed in this lesion.

III. Final Diagnosis

Taking into account the patient’s information (34-year-old female), lesion location in the left popliteal fossa, MRI and ultrasound characteristics, plus the known epidemiology and imaging features of “aggressive fibromatosis (Desmoid tumor),” the most likely diagnosis is:

Aggressive fibromatosis (Desmoid tumor, fibrosarcoma-like lesion)

For further confirmation, an ultrasound- or CT-guided biopsy could be performed for histopathological analysis, ruling out leiomyosarcoma or other soft tissue sarcomas.

IV. Treatment Plan and Rehabilitation

1. General Treatment Strategies:

• Surgical Resection:
  Surgical removal is often the primary approach for lesions with significant growth, severe symptoms, or impacted joint function. Ensuring clear margins is vital due to the tendency for local recurrence in aggressive fibromatosis.
• Radiotherapy:
  For cases with high recurrence risk post-surgery or incomplete resection, adjuvant radiotherapy can be considered to reduce local recurrence.
• Pharmacotherapy:
  Includes the use of steroids (e.g., local or intralesional steroid injections) and immunosuppressants for patients with active lesion growth or post-surgical recurrence. Some reports have also indicated efficacy with anti-estrogen therapy (e.g., Tamoxifen).
• Observation/Follow-up:
  For early-stage lesions with slow growth or minimal symptoms, monitoring and periodic follow-up may be chosen based on lesion size and patient complaints.

2. Rehabilitation / Exercise Prescription (FITT-VP Principle):

• Frequency (F):
  Recommended to gradually perform rehabilitation exercises 2-3 times per week, avoiding excessive load on the affected limb.
• Intensity (I):
  Engage in low-to-moderate intensity exercises, avoiding excessive stress on the posterior knee area. This should be monitored by the attending physician or a rehabilitation therapist, with incremental increases as tolerated.
• Time (T):
  Sessions of 20-30 minutes, possibly divided into shorter intervals initially. Given the patient’s history of limited knee range of motion, particular emphasis should be placed on extension and flexion exercises to restore flexibility.
• Type (T):
  Focus on range-of-motion exercises, mild strengthening for knee flexors and extensors, and non-weight-bearing or low-impact training (e.g., seated exercises or aquatic therapy). Resistance bands may be used as needed.
• Progression (P):
  Progress the duration and intensity incrementally in the absence of severe pain or discomfort. Regular follow-up is advised to assess for changes in the lesion, knee function, and pain. In case of recurrence or joint dysfunction, exercise programs may need modification or temporary discontinuation.

Throughout the rehabilitation process, protect the joint structures and avoid excessive traction on the popliteal region. If marked pain or swelling occurs, halt activity immediately and seek professional advice.

V. Disclaimer

This report is a reference analysis based on the available imaging studies and clinical history, and it does not replace an in-person consultation or professional medical assessment. Specific treatment plans should be formulated by specialists, in conjunction with pathological findings, laboratory results, and the patient’s overall condition.