14 April 2022: Textbook Updates

We have posted updates of the following topics:

Bone & joints > Osteomyelitis > Bacterial osteomyelitis (acute)
by Hans Magne Hamnvåg, M.D., Dariusz Borys, M.D.
Topic summary: Infection involving bone, rare due to use of antibiotics; usually pyogenic. Bacteria proliferate in bone, cause inflammation and necrosis. Classified on the basis of duration of illness and mechanism of infection. Hematogenous osteomyelitis occurs most commonly in children, more than half in children younger than 5 years. Diagnosis is established via culture obtained from biopsy of the involved bone. Chronic osteomyelitis develops in a subset of acute osteomyelitis due to: delayed treatment, inadequate antibiotics, incomplete surgical debridement of necrotic bone and weakened host defenses. Treatment: antibiotic therapy, surgical debridement.

Oral cavity & oropharynx > Potentially malignant & dysplasia > Dysplasia
by Veronica Cheung, M.Ch.D., Ruta Gupta, M.D.
Topic summary: Abnormal proliferation of oral epithelial squamous cells showing cytologic and architectural atypia. Oral epithelial dysplasia describes a spectrum of changes in the oral squamous mucosa, as it transforms from normal epithelium into a premalignant lesion with potential to develop invasive carcinoma (if not adequately treated). Presentation can be variable, ranging from asymptomatic lesions to nonhealing ulcers. Persisting lifestyle factors (smoking / tobacco, excess alcohol, areca nut) increases risk of recurrence / progression. Surgical management is the treatment of choice.

Soft tissue > Uncertain differentiation > Alveolar soft part sarcoma
by Laura Warmke, M.D., Jeanne Meis, M.D.
Topic summary: Rare sarcoma of uncertain histogenesis. Malignant mesenchymal neoplasm frequently composed of large, polygonal cells with abundant eosinophilic cytoplasm, a nested or pseudoalveolar growth pattern and PASD+ intracytoplasmic rhomboid or rod shaped crystals. ASPSCR1-TFE3 translocation is an instigating genetic event. Accounts for < 1% of all soft tissue sarcomas. Patient age range is 1 – 78 years (median: 25 years). Commonly involves deep soft tissues of the extremities (61%, predominantly the lower extremity), trunk (20%), internal organs (8%) and head and neck (9%). ASPS is not formally graded but considered to be high grade; initial course may seem indolent but overall prognosis is poor.

Stains & CD markers > BCL6
by Elena M. Fenu, M.D., Danielle Lameirinhas Vieira Maracaja, M.D.
Topic summary: Transcription factor located at 3q27 that is required for germinal center B cell formation and follicular helper T cell (TFH) differentiation. Proto-oncogenic transcription factor that is involved in regulating B cell response to DNA damage. Marker of germinal center differentiation (also CD10). Coexpression of BCL6 and BCL2 by immunohistochemistry is abnormal and can help distinguish follicular lymphoma (85 – 90% in grade 1 – 2, < 50% in grade 3) from reactive follicular hyperplasia. Large cell lymphomas with rearrangements of MYC, BCL2 or BCL6 (double or triple hit lymphomas) are classified as high grade B cell lymphomas and carry a poor prognosis.

Stains & CD markers > CD3
by Leonie Frauenfeld, M.D., Christian M. Schürch, M.D., Ph.D.
Topic summary: Common antibody for identifying T cells. Member of immunoglobulin superfamily on 11q23; also called OKT3. CD3 is a cell surface complex composed of 4 distinct subunits; these subunits are chains of integral membrane glycoproteins that associate with T cell antigen receptor (TCR) and are required for TCR cell surface expression and signal transduction. Cytoplasmic positivity in immature T cells (cCD3), while negative surface CD3 (sCD3); complete and membranous positivity in mature T cells (CD3). Most specific T cell antibody, usually used to identify T cells in benign and malignant disorders; most antibodies are directed against epsilon chain.

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