Musculoskeletal Oncology Practice Questions

Q: Which of the following tumors typically involves regional lymph nodes?

Synovial cell sarcoma. **Explanation:** In orthopaedic oncology, a fundamental rule is that **most primary bone and soft tissue sarcomas spread via the hematogenous route** (typically to the lungs). Lymphatic spread is rare, occurring in less than 3% of cases. However, certain specific tumors are notorious for involving regional lymph nodes. **1. Why Synovial Cell Sarcoma is Correct:** Synovial cell sarcoma is one of the classic exceptions to the rule of hematogenous spread. Along with Rhabdomyosarcoma, Clear cell sarcoma, Epithelioid sarcoma, and Angiosarcoma, it frequently metastasizes to regional lymph nodes. This makes lymph node assessment crucial in the clinical staging of these patients. **2. Why the Other Options are Incorrect:** * **A. Ewing Sarcoma:** This is a small round blue cell tumor that primarily spreads via the blood to the lungs and other bones. Lymph node involvement is extremely rare. * **B. Osteosarcoma:** The most common primary malignant bone tumor. It characteristically spreads via the bloodstream to the lungs ("skip lesions" are also a feature), but rarely involves the lymphatic system. * **C. Adamantinoma:** A slow-growing, low-grade malignant tumor typically found in the mid-shaft of the tibia. While it can metastasize to the lungs, lymphatic involvement is not a typical feature. **3. NEET-PG High-Yield Pearls:** To remember the tumors that spread to lymph nodes, use the mnemonic **"SCARE"**: * **S:** **S**ynovial Sarcoma * **C:** **C**lear cell sarcoma * **A:** **A**ngiosarcoma * **R:** **R**habdomyosarcoma * **E:** **E**pithelioid sarcoma **Clinical Note:** Synovial sarcoma is most commonly found near joints (though it rarely arises *from* the synovium itself) and often shows a characteristic **biphasic pattern** on histology and a **t(X;18)** translocation.

Q: Giant cell tumor of the tendon sheath is classified as which of the following?

Benign tumor. **Explanation:** **Giant Cell Tumor of the Tendon Sheath (GCTTS)** is a localized, slow-growing, and **benign** soft tissue tumor. It is the second most common tumor of the hand (after Ganglion cysts). Histologically, it is considered a localized form of **Pigmented Villonodular Synovitis (PVNS)**, characterized by the proliferation of synovial-like cells, multinucleated giant cells, and hemosiderin-laden macrophages. **Why Option D is Correct:** GCTTS is a neoplastic process, but it is strictly **benign**. It typically presents as a painless, firm, non-transilluminating nodule on the volar aspect of the fingers. While it has a high local recurrence rate (up to 10-20%) if not completely excised, it does not metastasize. **Why Other Options are Incorrect:** * **A. Traumatic:** While patients may recall a history of trauma, it is not the causative factor. It is a proliferative neoplastic process, not a post-traumatic reactive lesion. * **B. Infective:** There is no bacterial, viral, or fungal etiology associated with GCTTS. It lacks signs of inflammation like fever, redness, or purulent discharge. * **C. Malignant tumor:** GCTTS does not exhibit malignant features like rapid growth, systemic spread, or significant cellular atypia. Malignant transformation is extremely rare. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site:** Index and middle fingers (volar aspect). * **MRI Appearance:** Characteristic **low signal intensity** on both T1 and T2 weighted images due to the presence of **hemosiderin** (paramagnetic effect). * **Histology:** Look for "Foamy histiocytes" and "Touton giant cells." * **Treatment:** Marginal surgical excision. The main challenge is the high rate of local recurrence due to its proximity to digital nerves and vessels.

Q: Generally, radiotherapy should not be used for treating benign conditions. What is the only possible exception to this rule?

Extensive pigmented villonodular synovitis. **Explanation:** The general rule in orthopaedics is to avoid radiotherapy for benign conditions due to the risk of **radiation-induced sarcomatous transformation** and long-term morbidity. However, **Pigmented Villonodular Synovitis (PVNS)**, specifically the diffuse type, is a notable exception. **Why PVNS is the exception:** PVNS is a benign but locally aggressive proliferative disorder of the synovium. While surgical synovectomy is the primary treatment, the **diffuse form** has a very high recurrence rate (up to 40-50%). In cases where the disease is extensive, involves vital neurovascular structures, or recurs repeatedly after surgery, **low-dose external beam radiotherapy** is used as an adjuvant to achieve local control and prevent further joint destruction. **Analysis of Incorrect Options:** * **A. Chondromyxoid Fibroma:** This is a benign cartilaginous tumor. Radiotherapy is strictly contraindicated as it carries a high risk of inducing a secondary malignant transformation into post-radiation sarcoma. * **C. Benign Fibrous Histiocytoma:** This is treated by curettage and bone grafting. It is not radiosensitive, and surgery is curative. * **D. Desmoplastic Fibroma:** Although locally aggressive and difficult to excise, the primary treatment remains wide surgical resection. Radiotherapy is generally avoided due to the risk of malignant transformation into fibrosarcoma. **NEET-PG High-Yield Pearls:** * **PVNS Pathognomonic feature:** MRI shows "blooming effect" on Gradient Echo (GRE) sequences due to **hemosiderin** deposits. * **Giant Cell Tumor (GCT):** Another benign but aggressive tumor where radiotherapy is reserved only for "unresectable" lesions (e.g., spine/sacrum) due to the risk of transformation into malignant GCT. * **Radiotherapy in Orthopaedics:** Most commonly used for malignant tumors (Ewing’s Sarcoma) or palliative care in bony metastases.

Q: A patient with metastatic breast cancer presents with pathological fracture of femur. What is the best fixation method?

Long Intramedullary Nail. ***Long Intramedullary Nail*** - Provides **strong internal fixation** that can bear weight immediately, crucial for patients with a limited life expectancy due to metastatic disease. - Stabilizes the entire bone, preventing further **pathological fractures** in the diaphysis and allowing earlier mobilization and pain relief. *External Fixator* - Primarily used for **temporary stabilization** in severe open fractures or polytrauma, and not for definitive fixation of pathological fractures. - High risk of **pin tract infections** and patient discomfort, making it unsuitable for long-term management in cancer patients. *Dynamic Hip Screw* - Primarily used for **intertrochanteric hip fractures**, which are typically proximal femur fractures. - Less effective for **diaphyseal fractures** or for stabilizing bone weakened by metastatic disease along its entire length. *Plate and Screws* - While effective for some fractures, plates may not provide sufficient **load-bearing capacity** for extensively lytic or weakened bone in metastatic disease without extensive bone grafting. - Risk of **stress shielding** and subsequent re-fracture proximal or distal to the plate, especially when the intramedullary canal is compromised by tumor.

Q: Elderly female present with pain and swelling in the thigh. Xray shows multiple lytic lesions in distal femur with no periosteal reaction. Aspirate from the swelling shows homogenous serosanguinous fluid with RBCs. Which investigation can confirm the diagnosis?

Biopsy. ***Biopsy*** - A biopsy is the **definitive diagnostic tool** for establishing the presence of malignant cells that would cause lytic lesions and serosanguinous fluid in an elderly patient. - The findings of **multiple lytic lesions** in an elderly patient, coupled with serosanguinous fluid, strongly suggest a primary bone tumor or metastatic disease, which can only be confirmed histologically. *S. PTH levels* - **Elevated PTH** levels are indicative of **hyperparathyroidism**, which can cause bone resorption and lytic lesions (osteitis fibrosa cystica). - However, in this case, the fluid aspirate points towards a more localized, possibly neoplastic process rather than a systemic metabolic bone disorder as the primary concern. *S. Calcium levels* - **Hypercalcemia** can be associated with lytic bone lesions, particularly in cases of malignancy (e.g., **multiple myeloma** or **metastatic cancer**). - While supportive, calcium levels alone are insufficient to **confirm the specific diagnosis** of the underlying cause of the lytic lesions. *CD1a IHC* - **CD1a immunohistochemistry** is primarily used to diagnose **Langerhans cell histiocytosis**, a condition typically seen in children and young adults. - Given the patient's age and the imaging findings of multiple lytic lesions, Langerhans cell histiocytosis is an unlikely diagnosis, making CD1a IHC not the primary or confirming investigation.

Question 1

Which of the following tumors typically involves regional lymph nodes?

Accepted Answer

Synovial cell sarcoma

Answer

Ewing sarcoma

Answer

Osteosarcoma

Answer

Adamantinoma

Question 2

Giant cell tumor of the tendon sheath is classified as which of the following?

Accepted Answer

Benign tumor

Answer

Traumatic

Answer

Infective

Answer

Malignant tumor

Question 3

Generally, radiotherapy should not be used for treating benign conditions. What is the only possible exception to this rule?

Accepted Answer

Extensive pigmented villonodular synovitis

Answer

Chondromyxoid fibroma

Answer

Benign fibrous histiocytoma

Answer

Desmoplastic fibroma so extensive that it cannot be surgically excised

Question 4

A patient with metastatic breast cancer presents with pathological fracture of femur. What is the best fixation method?

Accepted Answer

Long Intramedullary Nail

Answer

External Fixator

Answer

Dynamic Hip Screw

Answer

Plate and Screws

Question 5

Elderly female present with pain and swelling in the thigh. Xray shows multiple lytic lesions in distal femur with no periosteal reaction. Aspirate from the swelling shows homogenous serosanguinous fluid with RBCs. Which investigation can confirm the diagnosis?

Accepted Answer

Biopsy

Answer

S. PTH levels

Answer

S. Calcium levels

Answer

CD1a IHC

Musculoskeletal Oncology — MCQs

Musculoskeletal Oncology — MCQs

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