B107 Tumors of the joints and muscles

Question 1

List the tumors of the joints

Answer 1

Primary neoplasms are rare, and Benign primary tumors are much mor common than malignant ones

Joint tumors derive from the various tissues of the joint:

1. Ganglion and Cynovial cysts
2. Synovial tumors
   
   1. Tenosynovial Giant cell tumor
      
      • PVNS - Pigmented villonodular synovitis, previous name
      • GCT - Giant cell tumor of the Tendon Sheath alternate name
3. Vascular tumors
   
   • Hemangioma
   • Angiosarcoma
4. Fibrous tumors
   
   • Fibrosarcoma
5. Cartilage tumors
   
   • Chondroma
   • Chondrosarcoma.

Question 2

Tenosynovial Giant Cell Tumor

Question 3

Morphology and histology of Tenosynovial Giant Cell tumors

Answer 3

Both are Red/brown to orange/yellow. (pigmented)

Pigmented Villonodular Synovitis:

• The diffuse variant of the tumor, the synovium gorws into a shag carpet like matt of folds, finger-like projections, and nodules (hence, Villi Nodular).
• It typically affects a single joint, in the knee 80%, hip or ankle.

Tenosynovial Giant Cell Tumor:

• Presents as a distinct, well circumscribed mass in a tendon sheath of the synovial capsule.
• Typically affects a single joint, in the wrist or finger tendon sheaths.

Histology

• Both are composed of neoplastic synoviocytes
• Contain many hemosiderin-filled macrophages.
• Osteoclast-like Giant cells
• Sparse hyalinized stromal collagen, it is mostly cellular.

Question 4

Presentation, symptoms, and prognosis of Tenosynovial Giant Cell Tumors

Answer 4

PVNS Pigmented Villonodular synovitis

• Presents as pain with immobility or joint locking
• Recurrent joint swelling
• Aggressive forms can invade into adjacent bone and soft tissue.

TGCT Tenosynovial Giant Cell Tumor

• Painless
• Slowly growing mass in the wrist or finger joints.

Neither form is metastatic, and both are curable by surgery, but they have a high rate of recurrence.

Question 5

TGCT and PVGS associated mutations

Answer 5

t1,2 translocation.

Fuses a collagen promoter sequence to the coding sequence of M-CSF growth factor.

Question 6

What types of cells do most soft tissue tumors arise from?

Answer 6

They seem to arise from pluripotent mesenchymal stem cells and are usually not from malignant transformation of mature mesenchymal cells.

Question 7

General fact about tumors of the joints

Answer 7

Primary neoplasms of joints are uncommon and usually benign.

Question 8

What is a ganglion of a joint?

Answer 8

A small pseudocyst located near a joint capsule or tendon sheath.

Formed by cystic degeneration of the connective tissue and coalescence of small adjacent cysts.

Contents are similar to synovial fluid.

Are generally totally asymptomatic.

Incredibly, they are often treated by ‘bible therapy.’ smashing them with a book so they burst…

Question 9

Synovial Sarcoma, morphology, histology, and associated genetic change

Answer 9

Name is basically a misnomer.

• The neoplastic cells are not related to synovial cells and likely arise from a pluripotent mesenchymal progenitor cell.
• Only 10% of synovial sarcoma occur in the articular synovium.

They are approximately 10% of all soft tissue sarcomas, and usually develop deep in the soft tissues around the joints of the extremeties, usually around the knee (60-70%). Has a pale yellow/tan appearance

• Aggressively locally invasive,
• Metastasize to lung, bone, and lymph nodes.

Histology:

Neoplastic cells can be monophasic or biphasic, usually biphasic.

• dense ​spindle cells
• with or without cuboidal/columnar epithelial cells forming tubules/glands.

Genetic:

• An X;18 translocation producing a fusion protein transcription factor.

Question 10

Synovial sarcoma, presentation, treatment, prognosis

Answer 10

Presents as a deep, invasive mass in the soft tissue around the large joints of hte arms and legs, usually the knee.

Treatment: Aggressive chemotherapy and limb-sparing surgery.

Prognosis:

5yrS is 25-60%

10yrS is 10-30%

Question 12

Fibrosarcoma, everything

Answer 12

Malignant neoplasia of fibroblasts

Soft, infiltrative mass, that grows slowly, with focal necrosis and hemorrhage.

Originates in the deep soft tissue, thigh, knee, retroperitoneum.

Usually present for years by the time of diagnosis.

Metastasize in 25% of cases, usually to the lungs by hematogenous spread.

They require wide excision and have a high rate of recurrence.

Histology:

• Can be well differentiated with spindle cells, often arranged in a herringbone alternating pattern of orientation
• Very undifferentiated with high mitotic figures and pleomorphism
• Most are densly cellular, but can also present as Myxofibrosarcoma variant with abundant myxoid deposition.

Question 13

List the Muscle tumors

Answer 13

Smooth muscle tumors:

• Leiomyoma
• Leiomyosarcoma

Skeletal muscle tumors:

• Rhabdomyoma
• Rhabdomyosarcoma

Question 14

Leiomyoma everything

Answer 14

Benign, smooth muscle tumors.

They are common, and can arise from any smooth muscle cells in the body. Most commonly in the uterus and skin.

Morphology:

• Large, white, whorled cut surface
• Well circumscribed tumor, in the uterus frequently are multiple.

Histology:

• Bundles of well differentiated smooth muscle cells. May contain some calcified foci.

Question 15

Leiomyosarcoma, everything

Answer 15

Epidemiology:

• 10-20% of soft tissue sarcomas
• More common in females

Locations:

• Skin of the extremities
• Deep soft tissues of the extremities
• Retroperitoneally around the inferior vena cava (extremely rare)
• Uterus - a rare tumor of the uterus.

Presentation:

• Firm, painless mass
• Retroperitoneal ones can become very large before presentation, usually present with systemic cancer symptoms. Weight loss, night sweats, fatigue

Histology:

• Spindle shaped cells
• Cigar shaped nuclei
• More densely cellular than leiomyoma
• High degree of atypia, pleomrophic nuclei
• High mitotic figures

Prognosis:

• Superficial skin ones are usually noticed small and cured by excision
• Retroperitoneal ones have often metastasized and are lethal due to lung metastases.
• Uterine leiomyosarcomas are aggressive and often metastasize, and have a high rate of recurrenc.e

Question 16

Striated muscle tumors general facts

Answer 16

Skeletal muscle tumors are almost always malignant.

Skeletal muslce is generally non-proliferative and grows by hypertrophy not hyperplasia.

There is only one benign striated muscle tumor, Rhabdomyoma and it is most often found in the heart.

Question 17

Rhabdomyoma, everything

Answer 17

Are most often found in the heart

Cardiac Rhabdomyomas:

• Are the most frequent primary tumor of the heart in infants and children
• Present usually due to a valvular or outflow obstruction.
• Occur frequently in patients with tuberous sclerosis
• They have a high frequency of spontaneous regression, and are sometimes considered Hamartomas instead of neoplasms.

They occur but are rare in skeletal muscle, and are classified as adult, fetal, or genital types.

Histology:

Well differentiated muscle fibers that lack parallel organization, have adipose infiltration, and have large nuclei.

Question 18

Rhabdomyosarcoma, morphology and histology, stains

Answer 18

The most common soft tissue tumor of children and adolescents.

Occurs most often in the head, neck, or urogenital tract, surprisingly at sites where there is normally very little or not any skeletal muscle.

Morphology:

Embryonal: Forms the rare vaginal Sarcoma Botryoides, soft, gelatinous, grape like masses found in the genital tract of young girls.

Alveolar: Small, undifferentiated cells with little cytoplasm, and fibrous septa, which are loosely attached and form spaces in between the septa and cells that look like alveoli when prepared histologically.

Pleomorphic: pleomorphic, cellular, high atypia.

Histology:

The most important identiying characteristic is that they are Desmin expressing Rhabdomyoblasts. Many cells are also positive for Myogenin or MyoD.

Question 19

Rhabdomyosarcoma, presentation, treatment, prognosis

Answer 19

Appears as a soft tissue sarcoma of children before age 20

The embryonal variant specifically appears in infant females as the gelatinous, clustered tumor of the vagina, sarcoma botryoides.

Other types occur typically in the head, face, and neck.

They are aggressive and invasive

Embryonal variants have the best cure rates, pleomorphic the worst.

It is treated with surgery, chemotherapy, and radiation, and 2/3rds of children are totally cured.

Adults have much worse prognosis and often have the pleomorphic variant.