Mutation 5q21, mandible osteomas, abdominal desmoid (fibromatosis), familial adenomatosis polyposis with hundreds of colonic tubular adenomas and greatly increased risk of colonic carcinoma if colon not resected by age 39 years

Multiple enchondromas of hands & feet, increased risk (30-50%) of chondrosarcomas after age 40

Polyostotic fibrous dysplasia with bony trabeculae having a Chinese letter arrangement without osteoblastic rimming, fibrous stroma, polyostotic often hip/femur involvement with shepherd’s crook deformity, widened cortex with ground-glass appearance, isosexual precocious puberty in females with early menarche, café-au-lait macules with irregular coast of Maine periphery, slightly increased risk of osteosarcoma

Type II lethal in infancy, deforming type III, majority autosomal dominant, x-ray generalized osteopenia with multiple bone fractures, short stature, abnormalities in synthesis of type 1 collagen, blue sclera, gray opalescent teeth with chips/fractures due to dentinogenesis imperfecta

Point mutation in Fibroblast Growth Factor Receptor 3 on 4p16.3, short extremities due to premature deposition of bony struts at growth plate, overgrowth of disorganized chondrocytes not in columns, large head with prominent forehead & depressed nasal root, normal intelligence, normal reproductivity, sporadic mutations, autosomal dominant

Vitamin D deficiency in children, causes include malnutrition, liver disease, renal insufficiency, lack of sunlight exposure, bowing of legs, knobbiness/nodules “rachitic rosary” at costochondral junctions, flattened occiput if infant, disorderly arrangement of chondrocytes with lack of columns, excess unmineralized osteoid, x-ray widened growth plate with cup shaped metaphysis and generalized osteopenia

Vitamin D deficiency in adults, excess unmineralized osteoid with widened osteoid seams, generalized osteopenia, fractures, deformities with kyphoscoliosis

Primary postmenopausal Type I due to decreased estrogen, decreased osteoprotegerin & increased osteoclastic activity, primary senile Type 2 in males and females, secondary causes include endocrine, e.g., Cushing’s disease or syndrome, drugs, thinning/loss of trabeculae with normal mineralization, compression fractures in thoracic/lumbar spine so short stature, increased fracture risk

Associated with increased serum calcium due to increased parathyroid hormone, primary single pituitary adenoma, secondary with nodular hyperplasia of 4 parathyroid glands with renal insufficiency/failure; dissecting osteitis with tunneling, increased osteoclastic activity with bone resorption, fibroblastic replacement

2^nd-3^rd decade, diaphysis of long bones, small blue round cell tumor with islands of hyaline cartilage, poor prognosis 28% at 5 years, lytic lesion on x-ray

Involve bones of sinus (ethmoid or frontal) or maxilla, thickened bony trabeculae with woven and lamellar bone, if multiple involving mandible think of Gardner syndrome 

Most common primary matrix producing malignancy of bone, malignant osteoblasts, more common in males, 2 peaks with largest in 2^nd-3^rd decade and second peak in elderly as secondary osteosarcoma which is unresponsive to therapy with grave prognosis; early hematogenous spread to lungs, 20% with primary osteosarcoma have lung mets at presentation, painless or painful mass most often around knee (distal femur, proximal tibia)

Codman triangle lifting of periosteum with discontinuity forming a triangle, ivory like density on x-ray, extension of ivory like density into soft tissue indicative of cortical destruction with soft tissue extension, pathognomonic “lacy” or lacelike osteoid, many mitoses often some atypical, pleomorphic osteoblasts, osteoblastic type has ivory like density, amount of necrosis inversely related to prognosis, poor survival with increased necrosis

t(11;22), small blue round cell tumor, 1^st-2^nd decades, permeative moth-eaten diaphyseal lesion with cortical destruction & soft tissue extension, abnormal lamellated periosteal reaction, many mitoses, necrosis, PAS+ cytoplasm due to glycogen, CD99+, vimentin+,

aggressive tumor, requires chemotherapy, radiation, confirmation t(11;22)

Permeative or motheaten on x-ray with continuous periosteal reaction, necrotic bone with empty lacunae and neutrophils, most common cause Staphylococcus aureus so see Gram positive cocci in clusters, other causes if IVDU or urinary tract infection include Klebsiella species, Escherichia coli, or Pseudomonas aeruginosa; Salmonella species in sickle cell anemia patients, also Salmonella in stool; Hemophilus influenzae type b or Streptococcus agalactiae (Group B strep) in pediatric cases, lytic lesion with periosteal reaction in x-ray in chronic phase, hematogenous in infant/child or direct spread/continguous infectious focus or implanted via trauma

Also known as degenerative joint disease, increasing incidence at >50+ years, principally due to mechanical wear and tear injury, increased TNFalpha & IL-1, fibrillation of articular cartilage with formation of joint mouse/mice (loose bodies) in synovial fluid, complete loss of articular cartilage called eburnation, subchondral cysts, subchondral osteosclerosis, involvement of major weight-bearing joints including hips, knees, spine; osteophyte formation, asymmetric, osteophytes at DIP joints in hands called Heberden’s nodes, stiffness in morning without decrease in symptoms with activity

autoimmune condition, HLADR4+, activated T lymphocytes, cytokines, female predominance, relapsing/remitting, present in 20s-30s, systemic condition so can have fever, proliferative synovitis with classic finding of lymphoid nodules & also plasma cells, proliferating synovium forms pannus which grows over and destroys articular cartilage and extends to involve supporting tendinoligamentous structures with joint instability, principally involves small joints of hands & feet, symmetric, stiffness in morning abates with activity, positive rheumatoid factor of IgM type; newer specific marker anti-cyclic citrillinated peptide positive very early in course; PIP & MCP principally involved, ulnar deviation, Swan neck deformity, subluxation at MCP joints, rheumatoid nodule with central fibrinoid necrosis and peripheral palisading of histiocytes &

lymphocytes over flexor surfaces – elbows or in visceral organs

Inborn error of metabolism with autosomal recessive inheritance, homogentisic oxidase deficiency, early diagnosis if mother notices black color in diaper, brown-black conjunctiva, early onset of crippling osteoarthritis with brown-black pigment deposits in articular cartilage with erosion, low back pain initially due to spine involvement, later hips & knees, many loose bodies, renal stones & renal failure, early onset of angina, coronary atherosclerosis, MI

S100 protein+, diagnostic cell is lipoblast which is pleomorphic cells with varying sized fat vacuoles which indent central enlarged hyperchromatic nucleus, or signet-ring like lipoblast with single cytoplasmic fat vacuole pushing an enlarged hyperchromatic nucleus to side

Well differentiated lipoma-like liposarcoma, also called atypical lipoma, good prognosis, 10% have dedifferentiated component with worse prognosis, marker ring & giant chromosomes derived from 12q13-15

t(12;16), typical lipoblasts mainly of which resemble signet ring cells, myxoid/mucoid background, delicate plexiform vascular network, middle age, deep soft tissue mass involving extremities or retroperitoneum, also popliteal mass

Malignant fibrous histiocytoma

(AKA pleomorphic sarcoma)

Malignancy of skeletal muscle, classic nuclear stain with myogenin and MYOD1

Botryoid variant superior prognosis, arise in a hollow viscus, most often urinary bladder or vagina, less often head & neck in nasal cavity; toddler-6 years, grossly has grape-like polypoid appearance, submucosal cambium layer with increased cellularity, underlying myxoid change with scattered tadpole cells and cells with eosinophilic cytoplasm & cross striations, nuclear myogenin & MYOD1 positive. not otherwise specified, 1^st decade, intermediate prognosis, most often head & neck area