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Flashcards in ICC Deck (25):

Small round blue cell differential (9)?

MR D LEMONS (Small round blue cell tumors)

  • Melanoma
  • Retinoblastoma
  • Desmoplastic Small Round Cell Tumor
  • Lymphoma (non-hodgkins, Burkitt's)
  • Ewing's
  • Medullary thyroid
  • Oligodendroglioma
  • Neuroblastoma
  • Small cell/synovial sarcoma


Name this entity.

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  • WHO grade 2 tumor
  • Bland
  • Can met and be locally aggressive
  • Most common location: tibia
  • Marked surrounding sclerosis
  • Stain: CK+

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Middle aged female with few thickened, erythematous patches on trunk.

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Morphea (localized scleroderma)

  • Square bx sign (bottom of punch doesn't taper)
  • Dense collagen in dermis
  • Lack of adnexal structures

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67 yo M w/ elevated PSA.

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Atrophic adenocarcinoma of the prostate with nuclei showing marked enlargement with frequent prominent nucleoli, diagnostic of adenocarcinoma. Note that some of the neoplastic glands are so atrophic that out of context, they would not be recognizable as malignant.


Patient with VHL and large cerebellar mass.

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  • High vascularity - many small vessels.
  • Polygonal-shaped stromal cells with:
    • Hyperchromatic nuclei.
    • Vacuolated cytoplasm.
  • Inhibin +
  • VHL Associated
    • Hefner's tumor also associated
      • AKA: Endolymphatic sac tumor
  • Chr 3

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Prostate cores:

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  • Medium to large glands with architectural changes 
  • Described as "epithelial hyperplasia".
  • Diagnosed on basis of nuclear changes.
  • Hyperchromatic nuclei - key (low power) feature.
  • Nucleoli present - key (high power) feature.
  • Often increased NC ratio.
  • Nuclear enlargement - usually subtle/appreciated at high magnification only.
  • Tinctorial changes of the cytoplasm - usually amphophilic (red) or basophilic (blue).


26 yo M

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Calcinosis Cutis

  • If patches of muscle in the dermis indicates scrotal skin (or other 'feel good' skin, i.e. Nipple, vulva, etc)
  • Granulomatous inflammation
  • Calcifications
  • Epithelial layering w/ giant cells


Pregnant female.

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Retroplancetal hemorrhage (c/w abruption)

  • Maternal surface of placenta
  • Clot w/ red cells going into and intermixing w/ decidua
  • Clinical: abruption, Histo: retro placental hemorrhage
  • Areas of organization, hemosiderin laiden macs: chronic abruption
  • Can also see intravillous hemorrhage


36yo F, uterine mass.

Necrosis and pleiomorphism

Desmin and p53+

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  • Usually a cellular lesion.
  • Fasciclar arrangement:
    • Whorled look at low power.
    • Groups of spindle cells cut peripendicular to their long axis adjacent to groups of spindle cells cut in the plane of their long axis.
  • Features of malignancy (usually need 2 of 3): 
    • Nuclear atypia.
    • Tumour cell necrosis. Should be patchy/multifocal.
    • Zonal necrosis is suggestive of vascular cause.
    • Mitoses - key feature




Endometrial stromal sarcoma

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67yo M w/ elevated PSA.

What type and grade?

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Prostate adenocarcinoma, Gleason 4:

  • Loss of gland lumina.
  • Gland fusion.
  • Benign looking cords ('hypernephroid pattern').
  • Cribriform.
  • Glomeruloid pattern - resembles a glomerulus



Young male; skin.

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Spitz Nevus

  • Compound involvement of maelanocytes
  • Circumscribed
  • Symmetric
  • Pagetoid scatter
  • Rette bridging
  • Epithelioid cells, spindled cells
  • Clefts and nests
  • "Hanging Banana" dark rete

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65yo M w/ SOB, cough and emphysematous change and honeycombing on radiology.

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Usual Interstitial Pneumonia (UIP)

Shows 'diffuse' pattern.

Uncommon under 50yoa.

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3yo M w/ fever, anemia and bone pain presents with multiple lytic lesions in femur.

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Langerhan's Cell Histiocytosis (LCH)

  • Groups of histiocytes w/ 'coffee bean' nuclei and abundant foamy cytoplasm
  • Stellate fibrosis
  • +/- Eosinophils
  • IHC:
    • CD1a +
    • S100 +
    • CD207 (Langerin) +
  • Molecular: 
    • MC: BRAF V600E mutations
    • MAP2K1 are common in those w/o BRAF mutations

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60 yo M w/ chronic HBV infection.

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Hepatocellular Carcinoma (HCC)

  • Pseudoglandular formation
  • Unpaired arteries
  • Thickened hepatic plate (>3 cells)
  • Mimicks:
    • Bile duct adenoma
    • Von Meyenberg complex

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What is this lesion?

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  • Verrucay bodies (palisaded, zebra-stripe like areas)
  • Antoni A/B areas
    • A = cellular
    • B = paucicellular
  • Diffuse S-100 +
  • If nuclear pleomorphism, think MPNST
    • Especially if NF1

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27 yo M w/ peripheral mass.

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Solitary Fibrous Tumor (SFT)

  • Features:
    • Spindle cells in a patternless pattern.
    • Occasionally epithelioid cells - rare.
    • Hemangiopericytoma-like area (staghorn vessels).
    • Keloid-like collagen bundles - key feature.
    • +/-Well-circumscribed (common).
  • Criteria for malignancy:
    • Necrosis.
    • Mitoses >4/10 HPF -- definition suffers from HPFitis.
    • Increased cellularity.
    • Marked nuclear atypia.
    • Infiltrative margin.

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44yo F with erythematous plaque.

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Mycosis Fungoides (Cutaneous T-cell Lymphoma)

  • General
    • Mycosis fungoides - is a subtype (???).
    • CTCL is more common than cutaneous B-cell lymphoma (CBCL).
  • Stages
    • ​Like Kaposi sarcoma:
      • Patch.
      • Plaque.
      • Nodular.
  • Microscopic
    • Atypical lymphocytes:
      • Have folded "cerebriform" nuclei; Sezary-Lutzner cells.[3]
    • Grouping:
      • Nests in the epidermis - known as "Pautrier microabscesses".
      • Single lymphocytes in epidermis - without accompanying edema.
      • Short linear arrays of lymphocytes along the basal layer of the epidermis; "epidermotropism".
  • DDx:
    • Lymphomatoid papulosis.


Young male with firm nodule.

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Scrotal Calcinosis (calcinosis scroti)

  • Skin w/ patches of muscle in the dermis, indicated scrotal skin (or other 'feel good' skin, i.e. Nipple, vulva, etc)
  • Granulomaatous inflammation
  • Calcifications
  • Epithelial layering w/ giant cells


Uterine mass.

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  • Features:
    • Usually a cellular lesion.
    • Fasciclar arrangement:
    • Whorled look at low power.
    • Groups of spindle cells cut peripendicular to their long axis adjacent to groups of spindle cells cut in the plane of their long axis.
  • Features of malignancy (usually need 2 of 3): 
    • Nuclear atypia.
    • Tumour cell necrosis.Should be patchy/multifocal.
    • Zonal necrosis is suggestive of vascular cause.
    • Mitoses - key feature - definitions suffer from HPFitis


Eye lesion.

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Pthisis Bulbi.

  • Clinical
    • End stage of many diffuse ocular diseases
    • Usually submitted by the ophthalmologists with the diagnosis of “blind painful eye”
    • Marked atrophy and shrinkage of eye ball
  • Microscopic
    • Marked shrinkage and disorganization of eye (Fig. 25.8)
    • Corneal scarring with or without vascularization
    • Thickened sclera
    • Profound disorganization of intraocular tissues
    • Foci of calcification and ossification are usually observed

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Recent transplant.  Endocardial bx.

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Quilty Effect

  • General
    • Can be confused for rejection.
    • Benign behaviour.
  • Trivia
    • The name Quilty comes from the patient in which this was first recognized.
  • Microscopic
    • Lymphocytes in clusters (B cells and T cells).
    • Associated with the endocardium ("endothelium of the heart"), i.e. on the surface - key feature.
    • Often have capillaries in centre; usu. not associated with large blood vessels.
    • Lymphocytes separated by collagen.


GI biopsy.

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MALT (Marginal Zone) Lymphoma

  • Small (lymphoid) cells that may be plasma cell-like (plasmacytoid):
    • +/-Clockface nucleus.
    • +/-Eccentric nucleus.
    • +/-"Lymphoepithelial lesion" - gastric crypts invaded by a monomorphous population of lymphocytes.
      • Features:
        • Cluster of lymphocytes - three cells or more - key feature.
          • Single lymphocytes don't count.
        • Clearing around the lymphocyte cluster.
      • Not specific for MALT lymphoma, i.e. may be seen in other types of lymphoma.
  • DDx:
    • Other small cell lymphomas.
    • DLBCL - should be a distinctive region at low power
  • Other:
    • Translocation: t(11:18) 
    • CD19, 20, 22, 79a
    • Associated w/ H. Pylori
    • Stomach most common, can also occur anywhere along GI tract or eye

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50 yo M.  Wide local excision of arm mass.

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Dermatofibrosarcoma Protuberans (DFSP)

  • Microscopic
    • Dermal spindle cell lesion with storiform pattern.
    • Spokes of the wheel-pattern.
    • Contains adipose tissue within the tumour -- key feature.
    • Described as "honeycomb pattern" and "Swiss cheese pattern".
  • Notes:
    • Adnexal structure within tumour are preserved -- this is unusual for a malignant tumour -- important.
  • DDx:
    • Dermatofibroma - main DDx
      • has entrapment of collagen bundles at the edge of the lesion.
    • Dermatomyofibroma.
    • Nodular fasciitis.
  • DDx of storiform pattern:
    • DFSP.
    • Dermatofibroma.
    • Solitary fibrous tumour.
    • Undifferentiated pleomorphic sarcoma.

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Uterine mass, 60yo F.

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Malignant Mixed Mullerian Tumor (MMMT/Carcinosarcoma)

  • Biphasic tumour:
    • Malignant glandular component (adenocarcinoma).
    • Malignant stromal component (one of the following):
      • Homologous type (tissue native to uterus):
        • Smooth muscle (leiomyosarcoma).
        • Fibrous tissue (fibrosarcoma).
      • Heterologous type (tissue not native to the uterus):
        • Skeletal muscle (rhabdomyosarcoma).
        • Cartilage (chondrosarcoma).
        • Bone (osteosarcoma).
      • Undifferentiated sarcoma (pleomorphic undifferentiated sarcoma).
  • DDx:
    • Undifferentiated endometrial sarcoma.
  • Adenosarcoma of the uterus.

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Frontal lobe mass

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Anaplastic Oligodendroglioma

  • Cells resembling fried eggs (oligodendrocytes) with:
    • Round nucleus - key feature.
    • Distinct cell borders.
    • Moderate-to-marked nuclear atypia.
    • Clear cytoplasm - useful feature (if present).
  • Anaplastic (grade III) criteria:
    • "Significant" or "brisk" mitotic activity.
    • That means for most neuropathologists >= 6 mitoses per 10 HPF.
    • Microvacular proliferation.
    • Necrosis.

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