Dermatologic neoplasms

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Dermatologic cancer can be deadly. Collectively, they are the most common forms of cancer.

Squamous cell carcinoma

Precursor:[1]

  • Actinic keratosis (solar keratosis).
    • Clinical: yellow-brown scaly, patches, sandpaper sensation.
  • Keratocathoma - see non-malignant skin disease.
    • Some don't believe this entity exists.
      • These people sign this entity as low grade squamous cell carcinoma, keratoacanthoma type.[2]

Basal cell carcinoma

General

  • Very common.
  • Sun exposed skin.
  • Very rarely metastasizes - so rare... some don't think this is really a malignancy.

Clinical

  • Telangiectasias.
  • Raised pearly nodule.

As part of a syndrome

  • Nevoid basal cell carcinoma syndrome (NBCCS), AKA Gorlin syndrome.
  • Bazex syndrome (X-linked).[3]

Microscopic

Features:[4]

  • Artefactual separation of basal cell layer from underlying stroma.
  • Palisading hyperchromatic cells.

Notes:

DDx:

  • Trichoepithelioma.

Melanoma

  • AKA Malignant melanoma.
  • Main DDx: melanocytic lesions - especially if pigmented.
  • Known as the great mimicker in pathology; it may look like many things.

Clinical

  • ABCD = asymmetric, borders (irregular), colour (black), diameter (large).

Histology

  • Classic appearance of melanoma:
    • Loosely cohesive; mix of small nests of cells, single cells.
    • Mixed of spindle and ovoid cell morphology.
    • +/-Occasional large binucleated cells.
    • Cytoplasm: brown pigment (melanin).
    • Prominent (large) red nucleoli (like in serous carcinoma of the ovary).
    • Marked nuclear pleomorphism - variation in cell size, shape & staining (like in serous carcinoma of the ovary).
    • Nuclear pseudoinclusions (like in papillary thyroid carcinoma).

Notes:

  • Can look almost like anything.
    • Like it is said that sarcoidosis is in every internal medicine DDx... melanoma is every pathologic DDx.
  • Melanomas with:
    • An epitheloid cell morphology may mimic adenocarcinoma.
    • A spindle cell morphology may mimic spindle cell carcinoma (squamous cell carcinoma) or a sarcoma.

Stains

  • Fontana-Masson stain, stains melanin.[5]
    • May be useful to differentiate melanin from other brown stuff (e.g. lipofuscin, hemosiderin).

Electron microscopy

  • Melanosomes.

Image(s):

IHC

Standard panel:

  • S-100 +ve.
  • HMB-45 +ve.
  • Melan A (MART-1) +ve.

Notes:

  • The standard panel above is positive in other lesions also, e.g. cellular blue nevus.

Dermatofibrosarcoma protuberans

General

  • Abbreviated DFSP.
  • Dermal location.
  • Destroys adnexal structures.

Treatment

  • Wide excision.

Histology

  • Spindle cell morphology.
  • Contains adipose tissue within the tumour -- key feature.

IHC

Panel:[6]

  • CD34 +ve.
    • Usually negative in dermatofibroma.[7][8]
  • Factor XIIIa -ve.
    • Usually positive in dermatofibroma.[7][8]
  • S100 -ve (screen for melanoma).
  • caldesmin -ve (screen for muscle differentiation).
  • beta-catenin ???.
  • MIB-1 (proliferation marker) -- should not be confused with MIB1 a gene that regulates apoptosis.

DDx - histologic

  • Dermatofibroma - has entrapment of collagen bundles at the edge of the lesion.


Cutaneous T cell lymphoma

  • Abbreviated CTCL.
  • Mycosis fungoides - is a subtype (???).

Microscopic

  • Atypical lymphocytes:
    • Have folded "cerebriform" nuclei; Sezary-Lutzner cells.[9]
  • Grouping:
    • Nests in the epidermis - known as "Pautrier microabscesses".
    • Single lymphocytes in epidermis; "lymphocyte exocytosis".[10]
    • Short linear arrays of lymphocytes at the dermal-epidermal junction; "epidermotropism".[11]

Images:

Merkel cell carcinoma

General

Features:[12]

  • Rare.
  • Aggressive course/poor prognosis.
  • Neuroendocrine-like.[13]

Etiology:

  • Polyomavirus (?).[12]
  • Immunocompromised/immunosuppressed (e.g. organ transplant recipients).

Microscopic

Features:[14]

  • Nests or sheets or trabeculae.
  • Scant cytoplasm.
  • Nuclear moulding.
  • Multiple small nucleoli.
  • Usually mitotically active.

Image:

IHC

  • CK7 -ve, CK20 +ve

See also

References

  1. ↑ TN07 D6.
  2. ↑ RS. 17 May 2010.
  3. ↑ URL: http://emedicine.medscape.com/article/1101146-diagnosis. Accessed on: 6 May 2010.
  4. ↑ NEED REF.
  5. ↑ URL: http://education.vetmed.vt.edu/curriculum/VM8054/labs/Lab2/Examples/exfontana.htm. Accessed on: 5 May 2010.
  6. ↑ AP. May 2009.
  7. ↑ 7.0 7.1 PMID 7694515.
  8. ↑ 8.0 8.1 PMID 9129699.
  9. ↑ Klatt. AOP. P.385.
  10. ↑ URL: http://www.mdconsult.com/das/book/body/199872830-2/0/1709/I4-u1.0-B978-0-443-06694-8..50117-2--f2.fig. Accessed on: 6 May 2010.
  11. ↑ Klatt. AOP. P.385.
  12. ↑ 12.0 12.1 PMID 20418670.
  13. ↑ PMID 19395876.
  14. ↑ Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 491. ISBN 978-0781765275.
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