Basic approach to evaluating solid tissue tumor cytology (Proceedings)

Lump or bump

An epidermal, dermal, or subcutaneous mass lesion that is easily accessible to aspiration cytology

Goal of aspiration cytology

• To direct next step of therapy or diagnostics (at the minimum)

• To definitively diagnose the cause of the lesion

• To advise owners of most probable process

What makes it a lump?

• Expansion of tissue

• Tissue fluid

• Infiltration cells

• Overgrowth of resident cells

Overall question

• What is the process that is causing this expansion?

• Subquestions:

     o What is the treatment?

     o What is the prognosis?

Obtaining the sample

• Fine needle biopsy (aspirates)

     o Preferred method for masses

• Impression smear

• Scraping

• Swab

Staining

• Romanowsky stains

     o Metachromatic reaction

• Romanowsky-like stains (Diff-Quik)

     o Mast cells may not stain

What is the general process?

• Tissue fluid

• Cells

     o Inflammatory

     o Neoplastic

Fluid/cysts

• Keratin containing cysts

• Hematoma

Inflammation

• Identify leukocytes

• Search for and identify etiologic agents

What is the identity of the tissue on the preparation?

• Discrete: no cell to cell association

• Epithelial: tight clusters of round-ish cells

• Mesenchymal: loose aggregates of fusiform cells

Interpretation of samples

• Inflammatory versus neoplastic

• Neoplastic

     o Histogenesis: from what tissue has it arisen?

     o Benign v. malignant

Neoplasia histogenesis

• Discrete

• Epithelial

• Mesenchymal

Discrete neoplasms

• Lymphoma

• Mast cell tumor

• Histiocytoma

• Transmissable venereal tumor

• Malignant histiocytosis

• Plasmacytomas

• +/- melanoma

Mesenchymal neoplasms

• Dogma: poorly exfoliating

• Groups of cells appear off a "stalk"

• Many cells are individualized

• Fusiform shape

Epithelial neoplasms

• Sheets or clumps

• Acinar or ductal structures

• Round to polygonal versus fusiform/spindle

Criteria of malignancy

• Anisocytosis/anisokaryosis

• Pleomorphism

• Macrokaryosis (nuclei >10 microns)

• Increased nuclear to cytoplasmic ratio

• Multinucleation

• Abnormal mitoses

• Nuclear molding

• Macronucleoli

• Angular nucleoli

Specific lesions

• Lipoma: What if you had something then you have nothing?

• Sebaceous gland adenoma

• Masses on the south end (of a dog going north)

     o Two choices: apocrine gland adenocarcinoma or perianal gland tumor

• Histiocytoma

• Mast cell tumor

• Plasma cell tumor

• Epidermal or adnexal epithelial neoplasia

• Keratin containing cyst