Bone and Soft Tissue Pathology

These flashcards cover bone and soft tissue pathology, focusing on morphology, high-yield clinical points, immunohistochemistry, and molecular translocations for various tumors and diseases.

A lipoma is typically well-circumscribed, displays a homogeneous cut surface, and is characterized by the absence of ________ amplification on FISH.

MDM2

Angiolipoma usually presents as a painful mass on the forearm and is associated with mutations in ________ in over 80% of cases.

PRKD2

On immunohistochemistry (IHC), spindle cells and floret cells in pleomorphic lipoma show positivity for ________ and a loss of nuclear ________.

CD34, Rb1

Chondroid lipoma characteristically shows a ________ translocation, resulting in the fusion of the C11orf95 and MRTFB genes.

$$t(11;16)(q13;p12-13)$$

Lipoblastoma is a rare tumor seen in infants which genetically features rearrangements of ________ or the t(3;8)(p13;q21.1) translocation.

$$8q11$$

The atypical cells in Atypical Lipomatous Tumor (Well-Differentiated Liposarcoma) are most commonly found near or in the ________.

fibrous septae

Dedifferentiated Liposarcoma is molecularly characterized by the amplification of ________ and MDM2/CDK4 amplification on chromosome 12.

$$12q14$$

Myxoid Liposarcoma is characterized by a ________ matrix and "chicken-wire" vasculature, often associated with the ________ translocation.

myxoid, $t(12;16)(q13;p11.2)$

Nodular fasciitis is a benign, self-limiting lesion that features a ________ appearance and a ________ rearrangement on molecular testing.

"tissue culture", USP6

Elastofibroma typically occurs at the ________ of the chest wall and is associated with repetitive physical movements.

scapula (inferior margin)

Gardner-type fibroma is associated with ________ and features ________ of nuclear Beta-catenin on IHC.

Familial Adenomatous Polyposis (FAP) Syndrome, positivity

Inflammatory Myofibroblastic Tumor (IMT) is rare and often displays ________ rearrangement at chromosomal location ________.

ALK, $2p23$

Infantile fibrosarcoma is characterized by the ________ translocation, resulting in the ETV6-NTRK3 fusion.

$$t(12;15)(p13;q25)$$

Low-Grade Fibromyxoid Sarcoma is a malignant but indolent tumor that shows strong IHC positivity for ________.

MUC4

The morphological hallmark of Antoni A areas in a Schwannoma is the ________, which consist of nuclear palisading.

Verocay body

Malignant Peripheral Nerve Sheath Tumor (MPNST) typically shows a diffuse loss of nuclear ________ on immunohistochemistry.

H3K27me

Granular Cell Tumors are benign tumors of Schwannian origin that often cause ________ of the overlying epithelium.

pseudoepitheliomatous hyperplasia

PEComas are rare tumors defined by a ________ phenotype, staining positive for markers like HMB-45, SMA, and desmin.

myomelanocytic

Alveolar Rhabdomyosarcoma is characterized by sheets of monomorphic round cells and a recurrent ________ translocation in 75% of cases.

$$t(2;13)(q35;q14)$$

Tenosynovial Giant Cell Tumor (diffuse type) commonly involves the knee and is molecularly driven by ________ fusions.

COL6A3-CSF1

Myxomas, which may be associated with Mazabraud syndrome, typically harbor an activating mutation of ________ at codon 201.

GNAS

Alveolar Soft Part Sarcoma is characterized by a ________ translocation resulting in the ASPSCR1-TFE3 fusion.

$$der(17)t(X;17)(p11.2;q25)$$

Ewing Sarcoma features uniform round blue cells and a characteristic ________ translocation, most commonly fusing ________ and FLI1.

$t(11;22)(q24;q12)$, EWSR1

Solitary Fibrous Tumor consists of spindle cells in a "patternless" pattern and is molecularly defined by the ________ gene fusion.

NAB2-STAT6

Chondroblastoma is a benign tumor involving the epiphysis of long bones which IHC highlights with ________.

H3F3 K36M

The characteristic radiographic finding of a "sun-burst" or "hair on end" appearance is associated with ________.

Periosteal Osteosarcoma

Gout is characterized by ________ birefringent needle-shaped crystals, while Pseudogout features ________ birefringent rhomboidal crystals.

negatively, positively

Paget Disease of bone is characterized by a ________ of irregular reversal cement lines reflecting increased bone turnover.

mosaic pattern

Brown tumor of hyperparathyroidism is caused by elevated PTH, which leads to the upregulation of ________ on osteoblasts.

RANKL

Conventional Osteosarcoma is a high-grade malignancy that requires the presence of ________ bone formation for diagnosis.

neoplastic

The loss of ________ and/or MTAP expression on IHC, along with the deletion of ________ on FISH, is useful in the diagnosis of Malignant Mesothelioma.

BAP1, CDKN2A (p16)