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Question 101

Topic: Soft Tissue Tumors & Metastasis

A 45-year-old male is diagnosed with a 12 cm deep myxoid liposarcoma of the thigh. As part of his systemic staging workup, which of the following imaging modalities is uniquely indicated for this specific histologic subtype?

. PET/CT scan of the whole body
. MRI of the total spine
. CT scan of the brain with contrast
. Bone scintigraphy (Tc-99m)
. Ultrasound of the regional lymph nodes

Correct Answer & Explanation

. MRI of the total spine


Explanation

Myxoid liposarcoma has a unique propensity to metastasize to extrapulmonary locations, particularly the spine and other bones. Total spine MRI is standard in the staging workup for this specific subtype.

Question 102

Topic: Soft Tissue Tumors & Metastasis

A 45-year-old woman with a history of progressive proximal muscle weakness and a heliotrope rash is diagnosed with adult-onset dermatomyositis. What is the most critical screening evaluation required for this adult patient that is not routinely indicated for juvenile dermatomyositis?

. Echocardiography for cor pulmonale
. Bone densitometry
. Malignancy screening
. Renal ultrasound
. Electroencephalography

Correct Answer & Explanation

. Malignancy screening


Explanation

Adult-onset dermatomyositis has a strong association with underlying malignancies, particularly ovarian, lung, gastrointestinal, and breast cancers. Comprehensive malignancy screening is mandatory in adult patients.

Question 103

Topic: Soft Tissue Tumors & Metastasis

On a standard radiograph, the presence of multiple, uniform-sized, spherical calcified loose bodies within the joint capsule of the knee strongly suggests which of the following diagnoses?

. Primary synovial chondromatosis
. Secondary synovial chondromatosis
. Chondrocalcinosis
. Pigmented villonodular synovitis (PVNS)
. Lipoma arborescens

Correct Answer & Explanation

. Primary synovial chondromatosis


Explanation

Primary synovial chondromatosis is characterized by the metaplasia of synovium leading to multiple intra-articular cartilaginous nodules that calcify. A key distinguishing feature from secondary synovial chondromatosis (due to osteoarthritis) is that the loose bodies in the primary form are numerous and uniform in size.

Question 104

Topic: Soft Tissue Tumors & Metastasis

Deep lipomas of the extremities are classified as intramuscular or intermuscular. Which of the following statements regarding intramuscular lipomas is true compared to their subcutaneous counterparts?

. They have a higher rate of local recurrence after marginal excision
. They are uniformly associated with MDM2 amplification
. They do not infiltrate between skeletal muscle fibers
. They undergo malignant transformation to liposarcoma in 20% of cases
. They present with intense nocturnal pain responsive to NSAIDs

Correct Answer & Explanation

. They have a higher rate of local recurrence after marginal excision


Explanation

Intramuscular lipomas frequently infiltrate between muscle fibers, making complete enucleation more difficult. This leads to a higher local recurrence rate (up to 15%) compared to well-encapsulated subcutaneous lipomas.

Question 105

Topic: Soft Tissue Tumors & Metastasis

A 40-year-old male notes a slowly enlarging mass in his trapezius muscle. MRI reveals a well-defined mass with signal intensity identical to subcutaneous fat, interspersed with distinct, thick striations of skeletal muscle fibers. What is the most likely diagnosis?

. Atypical lipomatous tumor
. Intramuscular lipoma
. Spindle cell lipoma
. Myxoid liposarcoma
. Hibernoma

Correct Answer & Explanation

. Intramuscular lipoma


Explanation

An intramuscular lipoma characteristically infiltrates between skeletal muscle bundles. On MRI, this appears as a predominately fatty mass with traversing linear striations representing entrapped muscle fibers, distinct from the thick septations seen in liposarcomas.

Question 106

Topic: Soft Tissue Tumors & Metastasis
A 22-year-old male undergoes a pelvic radiograph following a minor sports injury. The radiograph incidentally reveals numerous small, well-defined, symmetric sclerotic foci clustered around the periarticular regions of the pelvis and proximal femurs. He is completely asymptomatic. If this patient were to exhibit associated cutaneous manifestations, what would be the most likely finding?
. Café-au-lait spots with smooth 'coast of California' borders.
. Dermatofibrosis lenticularis disseminata (connective tissue nevi).
. Subcutaneous hemangiomas with phleboliths.
. Plexiform neurofibromas.
. Sclerodermatous skin thickening over the affected bones.

Correct Answer & Explanation

. Dermatofibrosis lenticularis disseminata (connective tissue nevi).


Explanation

The incidental radiographic finding of multiple small, symmetric sclerotic foci in periarticular regions is characteristic of Osteopoikilosis ('spotted bone disease'). It is an autosomal dominant condition often caused by mutations in the LEMD3 gene. When osteopoikilosis is associated with cutaneous lesions, specifically connective tissue nevi (dermatofibrosis lenticularis disseminata), the condition is known as Buschke-Ollendorff syndrome. Café-au-lait spots with smooth borders are seen in Neurofibromatosis type 1. Hemangiomas are seen in Maffucci syndrome. Sclerodermatous changes are seen in Melorheostosis.