Week 1: tumors of mesenchymal origin Flashcards
Describe characteristics of Lipoma.
- most common soft tissue mass of adulthood
- gross: encapsulated soft yellow mass
- micro: mature white fat cells often indistinguishable from normal adipose tissue, no pleomorphism
- tx: excision
lipoblasts is key finding in diagnosis of liposarcoma. Well demarcated cytoplasmic lipid droplets, indentations in an irregularly hyperchromatic nucleus. May be multivacuolated or single droplet.
Describe characteristics of liposarcoma.
- rare in children
- gross: varies with subtype, myxoid is soft, mucoid, with small cysts
- micro: myxoid-small uniform undifferntiated mesenchymal cells iwth vairable number of lipoblasts. often with brnaching network of capillaries.
liposarcoma. Anastomosing capillaries with myxoid matrix. Seen in liposarcoma. Proliferation of lipoblasts.
Describe nodular fasciitis
- reactive lesion, secondary to trauma.
- freq. in young adults, does not recur even after partial excision
- several week hx of solitary rapidly enlarging mildly painful subQ nodular mass, most lesions are superficial, but may extend into fascia or muscle
- gross: several centimeter diameter with poorly defined margins
- micro: highly cellular, plump, immature appearing fibroblasts randomly arranged in whorls or fascicles with richly vascular myxoid matrix with extravasated RBCs or lymphocytes
- nucleoli prominent and mitotic figures numerous
Spindle cell growth. Seen in nodular fasciitis
low power image, highly pleomorphic cells. Abnormal mitotic figures. Elongated spindle cells, no mature cells. Seen in pleomorphic undifferentiated sarcoma
Higher power image of PUS. Abnormal mitotic figure
Embryonal rhabdomyosarcomas. Primitive tumors: small round basophilic cells with hyperchromatic nuclei. “small round blue cell tumors” more differentiated tumors: larger number of cells with rhabdomyoblastic differentiation. Rhabdomyoblast is diagnostic cell type-either globular cells with eccentric abundant eosinophilic cytoplasm or elongated cells that are strap like
strap cell (rhabdomyoblast) characteristic of rhabdomyosarcoma.
Describe rhabdomyosarcoma
- rare in adults, common in children
- features of striated muscle differentiation
- 3 types: embryonal (more common)-arises in head, GU, or retroperitoneum
- gross: soft friable gray white infiltrative mass, hemorrhagic, necrotic
- micro: embryonal subtype: undiff. small round or spindle shapped immature striated muscle cells with abudnant eosinophilic cytoplasm
- strap cells are feature of better diferentiated forms and have better prognosis
Describe Osteoid osteoma
- x-ray: gray oval mass (nidus) surrounded by dense reactive bone (osteosclerosis)
- benign tumors
- occurs in teens and 20s, boys more greatly affected, lower extremities
- pain is nocturnal, responds well to aspirin
- treated surgically
Describe osteosarcoma
- most common primary malignant bone tumor
- mostly adolescents, 1/4 in elderly (assoc. with Paget’s disease)
- strong assoc. with Rb gene
- produces osteoid=abnormal nonmineralized bone matrix
- frequently in metaphyseal areas of long bones, particularly around knee, and proximal humerus
- increased alkaline phosphatase in 50% patients
- gross: bulky gray white gritty tumor, with hemorrhage, necrosis, and cystic degeneration
- micro: haphazard osteoid or bone formation, poorly differentiated, highly pleomorphic cells, tumor giant cells commonly seen
Describe osteochondroma
- cartilage capped bony outgrowth that arises due to defect in growth plate, grows laterally into soft tissue
- results in pedunculated cartilage covered tumor
- mostly in children and adolescents
- in metaphysis of endochondral origin long bones, particularly knees
- gross: mushroom shaped or pedunculated bony protuberance covered by periosteum
- micro: superfically, cartilage cap composed of disorganized randomly arranged chondrocytes beneath which zone of chondrocytes with columnar arrangement that undergo irregular endochondral ossification
Osteochondroma. cartilage cap
