7 skin, bones, joints, soft tissues

SKIN

Sources: Dr. Padla’s ppt, Monique’s gross pic, Sec A and Sec B trans

Vitiligo

Well demarcated zones of pigment loss result from depletion of melanocytes that produce small melanin granules.

Note small macules of normal pigment within the patches of vitiligo

commonly found in the peri-oral, axilla, groin, knees, elbows and peri-orbital area.

not reactive to sunlight

Dysplastic Nevus

Gross: the periphery is flat (macule) while the center is elevated and dark in color (papule)

RED ARROW denotes the dermal papilla which delineates the invasion.

GREEN CIRCLE denotes the rete pegs where the nevus can be seen

bracket denotes that this is a COMPOUND NEVUS due to the crossing of the melanocytes beyond the dermoepidermal junction

Malignant Melanoma

Melanoma cells are larger than nevus cells, with irregular and prominent eosinophilic nucleoli. They grow as loose nests lacking the typical features of melanocyte maturation.

Malignant Melanoma

Langerhans Cell Histiocytosis

Immunohistochemical demonstration of CD1a antigen confirms the origin of these mononuclear cells from Langerhans cells

Langerhan cells: type of WBC that are phagocytic. They originally come from the bone marrow and upon maturation reside in the skin.

Pemphigus

initial intercellular edema leads to spongiosis wherein intercellular bridges are pushed or stretched out from each other. Fluid accumulation leads to a fishnet like appearance. This is more likely to rupture

Bullous pemphigoid

Not likely to rupture because blister is located subepidermally

Bones, Joints, and Soft Tissues

Sources: Dr. Padla’s ppt, Monique’s gross and histo pic, Sec A and Sec B trans , Armi’s notes

Bone in the process of repair Osteoblast: secretes osteoid matrix

which is initially soft; after 2 weeks, it becomes mineralized and becomes lamellar bone

Lamellae: layers connected by canaliculi

Process depend on application of forces or pressure; if without pressure, bone is resorbed by osteoclast

Note: osteoprogenitor cells

Note osteoclasts intermingled with osteocytes

Osteoclasts acidify environment for bone resorption

Calcium hydroxyapatite is broken down and reused by osteoblasts

Paget’s disease of the bone

Osteitis deformans Exhibits mosaic pattern or matrix

madness Defect in osteoclast There is a rapid osteolytic phase

therefore bone is thin

Hyperparathyroidism

The bone loss predisposes to microfractures and secondary hemorrhages that elicit an influx of macrophages and an ingrowth of reparative fibrous tissue, creating a mass of reactive tissue, known as a brown tumor.

The brown color is the result of the vascularity, hemorrhage, and hemosiderin deposition, and it is not uncommon for the lesions to undergo cystic degeneration.

Osteonecrosis (Avascular Necrosis)

Femoral head with a subchondral, wedge-shaped pale yellow area of osteonecrosis.

The space between the overlying articular cartilage and bone is caused by trabecular compression fractures without repair.

Pyogenic osteomyelitis, gross

The drainage tract in the subperiosteal shell of viable new bone (INVOLUTUM) reveals the inner native cortex (SEQUESTRUM)

Pyogenic osteomyelitis, histologic

Pyogenic osteomyelitis, x-ray

PYOGENIC OSTEOMYELITIS

almost always caused by bacteria. Once in bone, the bacteria proliferate and induce an

acute inflammatory reaction. The entrapped bone undergoes necrosis within the first

48 hours, and the bacteria and inflammation spread within the shaft of the bone and may percolate throughout the haversian systems to reach the periosteum.

Sizable subperiosteal abscesses may form that can track for long distances along the bone surface.

Lifting of the periosteum further impairs the blood supply to the affected region, and both the suppurative and the ischemic injury may cause segmental bone necrosis

TB Osteomyelitis, gross

TB Osteomyelitis, histologic

TB Osteomyelitis, x-ray

TB Osteomyelitis

s/sx: pain on motion, localized tenderness, low-grade fevers, chills, and weight loss.

Severe destruction of vertebrae frequently results in permanent compression fractures that produce severe scoliotic or kyphotic deformities and neurologic deficits secondary to spinal cord and nerve compression.

Osteosarcoma, gross

Osteosarcoma,histologic

Osteosarcoma, x-ray

Osteosarcoma- Osteoblastic Type LEFT SHOULDER

Osteosarcoma

Grossly, they are big bulky tumors that are gritty, gray-white, and often contain areas of hemorrhage and cystic degeneration.

The tumor cells vary in size and shape and frequently have large hyperchromatic nuclei.

Enchondromatosis?

Outgrowing of cartilage in the epiphyses of long bones

Not a neoplasm Usually left alone unless impinging

on nerves of patients

Chondrosarcoma, gross

With lobules of hyaline and myxoid cartilage permeating throughout the medullary cavity, growing through the cortex and forming a relatively well-circumscribed soft-tissue mass

Chondrosarcoma, histologic

Chondrosarcoma, x-ray

Chondrosarcoma, gross

Chondroblastoma

Chondroblastoma with scant mineralized matrix surrounding chondroblasts in a chicken wire–like fashion

Ewing’s Sarcoma, x-ray

Ewing’s Sarcoma

Arising in the medullary cavity, Ewing sarcoma usually invades the cortex, periosteum, and soft tissue.

The tumor is soft, tan-white, and frequently contains areas of hemorrhage and necrosis.

It is composed of sheets of uniform small, round cells

They have scant cytoplasm, that is rich in glycogen.

There is generally little stroma. Necrosis may be prominent, and there are

relatively few mitotic figures in relation to the dense cellularity of the tumor

Giant cell tumor, gross

Giant cell tumor, histologic

Giant cell tumor, x-ray

Giant Cell Tumor

These are large, red-brown tumors that frequently undergo cystic degeneration.

They are mostly composed of uniform oval mononuclear cells that constitute the proliferating component of the tumor.

Scattered within this background are numerous osteoclast-type giant cells having 100 or more nuclei that resemble those of the mononuclear cells.

Necrosis, hemorrhage, hemosiderin deposition, and reactive bone formation are common secondary features.

Osteoarthritis

Severe osteoarthritis with small islands of residual articular cartilage next to exposed subchondral bone. 1, Eburnated articular surface. 2, Subchondral cyst. 3, Residual articular cartilage.

Excised synovium with fronds and nodules typical of pigmented villonodular synovitis (arrow).

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Nodular Fasciitis

A highly cellular lesion composed of plump, randomly oriented spindle cells surrounded by myxoid stroma. Note the prominent mitotic activity

Malignant Fibrohistiocytic tumor

There are fascicles of plump spindle cells in a swirling (storiform) pattern.

Rhabdomyosarcoma, gross

Rhabdomyosarcoma, x-ray

Rhabdomyosarcoma INTERCAPSULAR MASS

Rhabdomyosarcoma, histo

The rhabdomyoblasts are large and round and have abundant eosinophilic cytoplasm; no cross-striations are evident here

Alveolar rhabdomyosarcoma with numerous spaces lined by tumor cells

Rhabdomyosarcoma

Alveolar rhabdomyosarcoma with numerous spaces lined by tumor cells

Histologically the tumor is traversed by a network of fibrous septae that divide the cells into clusters or aggregates that creates a crude resemblance to pulmonary alveolae.

The tumor cells are moderate in size, and many have little cytoplasm.

Those in the center of the aggregates are dyscohesive, while those at the periphery adhere to the septae.

Peripheral nerve and skeletal muscle

Traumatic neuroma

Disordered orientation of nerve fiber bundles (purple) intermixed with connective tissue (blue)

Duchenne Muscular dystrophy

variation in muscle fiber size, increased endomysial connective tissue, and regenerating fibers (blue hue).

Nemaline myopathy

Numerous rod-shaped, intracytoplasmic inclusions within muscle fibers (dark purple structures)

Mitochondrial myopathy

A congenital myopathy Mitochondrial myopathy showing an

irregular fiber with subsarcolemmal collections of mitochondria that stain red with the modified Gomori trichrome stain (ragged red fiber).

Red inclusion in the mitochondria or parking lot inclusions