Oncology Lecture 3 – Cross-Synaptic Learning for the USMLE

Episode 92:  Learn the difference between carcinoma, sarcoma, mesenchymal tumors, oncogenesis, and the protooncogenes.

NEOPLASIA

I. Nomenclature: Benign vs. malignant

A. Difference between benign and malignant cancer:

Main difference – Benign usually does not metastasize, malignant has the capacity to metastasize. Exception: B9 tumor that metastasize: invasive mole (metastasize to lungs, but goes away).

B. Overview of Neoplasia

a) MC skin cancer INVADES but does not metastasize? basal cell carcinoma.

b) MC B9 tumor in woman is MC located in which organ? Uterus – it’s a leiomyoma; tumor of smooth muscle!

c) Fibroids – smooth muscle; become very hard

d) MC B9 tumor in male (yellow) = lipoma

e) B9 tumor of glands = adenomas (ie adrenal adenoma – thin adrenal cortex b/c it is functional; it could be making cortisol, therefore suppressing ACTH, and the zone fasiculata and reticularis would undergo ATROPHY…leads to Cushing’s. If tumor secreting mineralocorticoids – it is Conn’s syndrome, causing atrophy of the zone glomerulosa (GFR – salty sweet sex)

f) Tubular adenoma = MC precursor lesion for colon cancer (looks like strawberry on a stick)

C. Carcinoma vs. sarcoma

1. Carcinoma

Malignancy of epithelial tissue (3 epithelial tissues – squamous, glandular, and transitional)

a) Squamous carcinoma – how to recognize? Little swirls of increased redness (bright red) called squamous pearls;

b) Glandular carcinoma – Round glands, with something in the middle = adenocarcinoma

c) Transitional cell carcinoma – from bladder, ureter, renal pelvis (from genital urinary tract) – all with transitional epithelium. Therefore, 3 carcinomas = squamous, adenocarcinoma, and transitional cell carcinomas.

d) Example: Malignant melanoma – first step in management? Excision (b9 version = nevus), both are derived from melanocytes. This is the most rapidly increasing cancer in the USA, not MC. They are S-100 Ag “+” tumors – aput tumors

e) Aput Tumors: S-100 Ag “+” tumors – aput tumors; aput is precursor uptake decarboxylation, meaning that they are of neurosecretory or neural crest origin. Therefore, on EM, have neurosecretory granules. S-100 Ag is used to stain things of aput origin or neural crest origin (most, not all, will take up that Ag).

Examples of aput tumors: melanoma; small cell carcinoma of the lung; bronchial carcinoid; carcinoid tumor at the tip of the appendix; neuroblastoma (secretory tumor), ie 2 y/o with tumors all over skin, and on biopsy, it is S-100 “+”, tumor was from adrenal medulla, metastasize to skin.

2. Sarcomas

Sarcomas are malignancy of MESENCHYMAL tissue (not epithelial).

* Sarcoma of smooth muscle = leioymyosarcoma;

* Striated muscle = rhabdomyosarcoma;

* Fat = liposarcoma; (these are malignancies of mesenchymal tissue, while carcinoma’s are of epithelial tissue).

Examples:

a) Bone, see metaphysis, see Codman’s triangle, and sunburst appearance on x-ray b/c this tumor actually makes bone. Dx = osteogenic sarcoma (bone making sarcoma).

b) Biopsy from girl having necrotic mass coming out of her vagina, Vimentin and keratin “-“, and desmin “+”, dx? Embryonal rhabdomyosarcoma (see striation of muscle). This is the MC sarcoma of children (vagina in little girls and penis in little boys).

c) Movable mass at angle of jaw = mixed tumor (in parotid); ‘mixed’ b/c two histologically have two different types of tissue but derived from SAME cell layer (not a teratoma, which is from three cell layers),. MC overall salivary gland tumor (usually b9) = mixed tumor.

d) Teratoma = tooth, hair, derived from all three cell layers (ectoderm, mesoderm, and endoderm) Aka germ cell tumors – b/c they are totipotential, and stay midline. Ex. anterior mediastinum, or pineal gland; therefore, teratomas are germ cell, midline tumors.