Merkel Cell Tumor - RWellner

Merkel Cell Tumor - RWellner - Case Presentation Rachel B...

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Case Presentation Rachel B. Wellner, MD MPH The Mount Sinai Hospital Department of General Surgery Team IV Conference August, 2005
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Case Presentation HPI: 75 year old male presents with a right thigh mass. PMHx: HTN, right forearm keratoacanthoma PSHx: 1997-98: Left breast Ca s/p left MRM and prophylactic right simple mastectomy (BRCA+) and underwent course of CMF 1987: Suprapubic prostatectomy (benign disease) 1929: Mastoid resection
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Case Presentation ROS: Denies constitutional symptoms Meds: HCTZ, prinivil, arthrotec, ASA, tamoxifen (d/c’d) PE: ~3cm round, mobile, superficial mass on right posterior thigh; no lymphadenopath Course: The patient underwent excision of 3cm mass.
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Case Presentation Pathology: Malignant Merkel Cell tumor Immunohistochemical studies Strong EMA (epithelial membrane antigen) and CK20 positivity (dot-like perinuclear stain) Focally positive for NSA and chromogranin
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Discussion: Merkel Cell Carcinoma (MCC)
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General Neuroendocrine tumors Embryologic origin is the neural crest cells. Various distribution (thyroid, pituitary, GI tract, pancreas, adrenal medulla, lungs) but related by common embryologic derivation Synthesis of peptide hormones and amines arising from specific precursors (Amine Precursor Uptake and Decarboxylation, APUD) Pearse: APUDomas (term neuroendocrine denotes identification of specialized APUD cells in CNS/PNS that utilize endocrine or paracrine transmission rather than synaptic).
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General Features Gross histology: trabecular, glandular, mixed, poorly differentiated. Histochemical analysis: silver staining with argentaffin cells argyrophilic cells for well-differentiated lesions. Electron microscopy: demonstrates the dense core granules of the neuroendocrine cells. Immunohistochemical Markers Cytoplasmic Constituents: Neuron-specific enolase, a glycolytic enzyme found in the cytosol (non-specific for NE cells). Granule Contents: Chromogranins A,B,C- soluble proteins located in dense- core secretory granules Plasma membrane constituents: receptors for peptides or neurotransmitters (somatostatin, glutamate, and gamma-aminobutyric acid), and neural cell adhesion molecules.
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MCC: Description The Merkel cell is found in the skin of fish, amphibians, reptilians, avians, and mammals. Possesses both epithelial and neuroendocrine elements. Immunohistochemical studies demontsrate the presence of neuron-specific enolase (NSE). Arise during the 8th gestational week and are postulated to be derived from a primitive epidermal stem cell Merkel cells are located in the basal layer of the epidermis and cluster in areas of sensory perception. Function unclear, may be involved in mechanoreception. Induction or stimulation of perifollicular or dermal nerve plexuses Stimulation of keratinocyte proliferation and maintenance of their differentiation Release of various bioactive substances to the dermis.
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MCC Merkel cell (Tastzellen cell) first described in 1875 by German
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