Dermatologic neoplasms

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

Squamous cell carcinoma

Precursor:

• Actinic keratosis (solar keratosis).
  • Clinical: yellow-brown scaly, patches, sandpaper sensation.
• Keratocathoma - see non-malignant skin disease.
  • Some don't believe this entity exists - that it's a low grade SCC.

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).

Microscopic

Features:

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

Notes:

• There are various subtypes: http://www.pathconsultddx.com/pathCon/diagnosis?pii=S1559-8675%2806%2970110-3.

DDx:

• Trichoepithelioma.

Melanoma

• AKA Malignant melanoma.

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.
  • May be useful to differentiate melanin from other brown stuff (e.g. lipofuscin, hemosiderin).

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:

• CD34 +ve.
• 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.
• Grouping:
  • Nests in the epidermis - known as "Pautrier microabscesses".
  • Single lymphocytes in epidermis; "lymphocyte exocytosis".
  • Short linear arrays of lymphocytes at the dermal-epidermal junction; "epidermotropism".

Images:

• CTCL (jci.org).
• CTCL (mdconsult.com).

Merkel cell carcinoma

General

Features:

• Rare.
• Aggressive course/poor prognosis.
• Neuroendocrine-like.

Etiology:

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

Microscopic

Features:

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

IHC:

• CK7 -ve, CK20 +ve

Image:

• Merkel cell carcinoma (ispub.com).
• Merkel cell carcinoma - nested pattern (WC).

See also

• Dermatopathology.
• Cytopathology.