Gunshot Wound to Brain

CT brain shows a bullet wound with entry at the RT frontal lode and exit at the LT frontal lobe.  The wound cavity is filled with blood.  The inset shows a ballistic cavity from a bullet in a gelatin block.

When a bullet strikes a person, tissue is crushed. The bullet's forward movement creates a temporary tunnel that expands to a larger tunnel. The larger tunnel is considered to be a temporary "cavitation" wave. Tissues in the temporary cavity sustain damage from compression, deformation and shear. After a bullet passes through, the temporary cavity recoils , but with a remaining cavity, called the permanent cavity. Tissue of the permanent cavity may be damaged and nonviable. Secondary missiles, such as bullet and bone fragments, can result in additional damage

The wound is created by the physical damage of the bullet itself and cavitation. Cavitation is the formation of vapor bubbles in a flowing liquid in a region where the pressure of the liquid falls below its vapor pressure. Inertial cavitation is the process where a bubble in a liquid rapidly collapses (bursts), producing a shock wave. A shock wave is a wave that carries energy and can propagate through a medium. Shock waves are characterized by an abrupt, nearly discontinuous change in the characteristics of the medium with an extremely rapid rise in pressure, temperature and density.

Gastrointestinal Stromal Tumor

One of the most common mesenchymal tumors of the GI tract.  Patients may present with early satiety, gastrointestinal bleeding, vague abdominal pain. Actual obstruction is rare.  The tumor can be large by time the diagnosis is made and patients may present with metastases (usually liver). On imaging studies GISTs appear as intramural masses.
Internal calcifications may be present. As the tumor grows larger it can undergo necrosis and ulcerate. GISTs can directly invade adjacent structures in the abdomen. Mets are ususlly to the liver. Spread to the peritoneal cavity can be seen.Metastatic adenopathy  is uncommon. 70% of GISTs occur in the stomach, 20% in the small intestine and less than 10% in the esophagus. GISTs are  connective tissue tumors. They are thought to arise from interstitial cells of Cajal (part of the autonomic nervous system of the intestinethat control motility.)


Most GISTs arise from a mutation in the c-kit gene.  This gene encodes for a transmembrane growth factor receptor called stem cell factor (scf), a tryosine kinase receptor. Mutations to c-kit usually occur in the intracellular domain of the receptor and cause it to be active independent of scf binding. GISTs that do not have a c-kit mutation often have a mutatuion in a related tyrosine kinase receptor, platelet derived growth factor receptor alpha (PDGFR-a).

GIST tumors with c-kit or PDGFR-a mutations can be treated with Imatinib (GLEEVAC), a tyrosine kinase inhibitor.

Miettinen M, Lasota J. "Gastrointestinal stromal tumors: review on morphology, molecular pathology, prognosis, and differential diagnosis". Arch. Pathol. Lab. Med. 130 (10): 1466–78

Multiple Myeloma

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Radiographs of the left knee show a poorly marginated lytic bone lesion in the distal femur.  The patient eventually had a pathologic fracture throught that lesion (also shown). Lytic thoracic spine lesions were also doccumented by CT.  Peripheral blood smear was loaded with plasma cells.  These cells stain positive for CD 138 (inset).  SPEP revealed an IgG Kappa spike. Findings are consistant with multiple myeloma. 

CD 138, Syndecan 1,  is a protein which in humans is encoded by the SDC1 gene. Syndecans mediate cell binding, cell signaling, and cytoskeletal organization.  Syndecans are single transmembrane domain proteins that are thought to act as coreceptors, especially for G protein-coupled receptors. These core proteins carry three to five heparan sulfate and chondroitin sulfate chains which allow for interaction with a large variety of ligands including fibroblast growth factors, vascular endothelial growth factor, transforming growth factor-beta, fibronectin and antithrombin-1.  Altered syndecan-1 expression has been detected in several different tumor types. It is a useful marker for plasma cells

O'Connell FP, Pinkus JL, Pinkus GS . "CD138 (syndecan-1), a plasma cell marker immunohistochemical profile in hematopoietic and nonhematopoietic neoplasms". Am. J. Clin. Pathol. 121 (2): 254–63