Carcinomas arise from cells which are ectodermal or endodermal in
origin, and they are classified squamous, basal-celled or glandular (adenocarcinomas).
Sarcomas occur in connection with structures of mesoblastic origin, hence
fibrosarcoma, osteosarcoma. Germ cell tumours arise from germ cells (teratoma, seminoma,
thecoma). Ovarian cancer is an adenocarcinoma: it does not arise from oocytes.
Macroscopically,
squamous cell carcinomas are either proliferative or ulcerative. On section
solid masses of polyhedral cells are seen, which invade the deeper structures.
‘Cell-nests’ are usually apparent in slowly growing cases, and are due to
deeper cells becoming flattened and undergoing keratinisation. ‘Prickle’ (acanthotic)
cells are characteristic, and resemble those present in the epidermis.
Basal-celled
(syn. rodent ulcer)
See Chapter 36.
Glandular
Glandular carcinoma commonly occurs in the alimentary tract, breast and
uterus, and less frequently in the kidney, prostate, gall bladder and thyroid.
Three types of glandular carcinoma may be recognised:
• adenocarcinoma, so called
from the tendency of the cells to form acini, which resemble those of the gland
from which they are derived. The alveoli are ductless, and the walls are
composed of layers of cells which invade the surrounding tissues. The cells of
the primary growth, and even of the metastases, sometimes retain secretory
powers; bronchial adenocarcinomas are well known for this;
• colloid (mucoid) is a
degenerative process which develops in tumours arising from mucin-secreting
cells. The mucin permeates the stroma of the growth, which appears as a
gelatinous mass and is typically seen in the colon and stomach.
Lymphatics
by invasion and by embolism.
Implantation.
Implantation of carcinoma has been observed in situations where skin or mucous
membrane is in close contact with a primary growth. Examples of this ‘kiss
cancer’ are carcinoma of the lower lip affecting the upper, and carcinoma
of the labium majus giving rise to a similar growth on the opposite side of the
vulva. Recurrence after operation is occasionally due to implantation of
malignant cells in the wound. Examples of this mischance are the appearance of a
malignant deposit in the scar after suprapubic removal of a primary carcinoma of
the bladder, and nodules of carcinoma in the scar of the incision after
mastectomy for a carcinoma of the breast. When a cavity is involved,
free-floating cells from a carcinoma may spread like snowflakes all over its
serous surface. For the abdomen, transcoelomic spread is specially
notable when cells from a colloid carcinoma of the stomach gravitate on to an
active ovary and give rise to malignant ovarian tumours (Krukenberg’s tumour,
Chapter 51); intracavitary dissemination can also take place within the
pleura and cerebrospinal spaces.
Nerve
sheaths. Adenocarcinomas, especially pancreas, may disseminate along nerve
sheaths.
Grading
and staging
Grading.
Grading predicts the aggressiveness of a malignant neoplasm by characterising
its microscopic appearance taking into account the degree of differentiation,
nuclear and cellular appearance, architectural integrity and the proportion of
active mitoses.
• Grade 1: well differentiated;
• Grade 2: moderately well differentiated;
• Grade 3: poorly differentiated.
Tumour
Nodes
Metastasis
T1 2 cm or less.
N0 No nodes
M0 No metastasis
No skin fixation
T2 More than 2 cm,
N1 Axillary nodes
M1 Metastases
are
but less than 5 cm. movable (a) not
present
including
Skin tethered or
significant,
involvement of skit
dimpled. No
(b) significant
beyond breast, and
pectoral fixation
contralateral nodes
T3 More than 5 cm,
N2 Axillary
but less than 10 cm. nodes fixed
Skin infiltrated or
ulcerated. Pectoral
fixation
T4 More than 10 cm. N3 Supraclavicular
Skin involved but nodes. Oedema
not beyond breast,
of arm
Chest-wall
fixation
(i) Thus, for example, one patient may have an early carcinoma which is T1N0M0,
while in another late case the extent of the disease may be T2N2M1.
(ii) Manchester staging. This is a method of staging clinical spread of
carcinoma of the breast (see Chapter 46).
(iii)
Dukes’ staging. This is a method of classifying the spread of carcinoma
of the rectum and colon and is described in Chapter 60.
Sarcomas differ from carcinomas, not only in their derivation, but in
their earlier age incidence, as they are most common during the first and second
decades. Sarcomas often grow rapidly and dissemination occurs early via the
bloodstream (e.g. ‘cannon-ball’ secondary deposits in the lung from an
osteogenic sarcoma).
The
macroscopic appearance of a sarcoma varies considerably. As the word implies,
most tumours appear as a fleshy mass, but their consistency depends on the
relative proportion of fibrous and vascular tissue. Haemorrhage commonly
occurs owing to the very thin walls of the veins, which in some places are
represented merely by venous spaces.
Sarcomatous
cells may reproduce tissue similar to that from which the tumour originated,
e.g. osteosarcoma or chondrosarcoma. Sometimes a sarcoma develops in preexisting
benign tumours, such as fibroma or a uterine fibroid, and also in bones which
are affected by osteitis deformans (Chapter 26).
Fibrosarcoma
Fibrosarcoma is composed of spindle cells of varying lengths (the
rounder they are the more malignant they are), and occurs in muscle sheaths,
scars and as a fibrous epulis. A fibrosarcoma of a muscle sheath presents as an
elastic or firm and slowly growing swelling. Dilated veins over the tumour
suggest malignancy, and if not obvious they may be demonstrated by infrared
photography. On palpation the tumour often feels warm and pulsation may even be
detected. Fibrosarcomas not uncommonly arise in scar tissue, sometimes many
years after the scar developed. Sir James Paget described this as a ‘recurrent
fibroid’.
Treatment
of sarcoma
The spread of a fibrosarcoma is hastened by incomplete removal. The
moral is that wide excision with surrounding healthy tissues should be practised
in all cases. This may mean amputation in the case of a limb. If untreated
or if wide local excision is unsuccessful, a fibrosarcoma eventually fungates
through the skin. Metastases are widely scattered and, unfortunately,
radiotherapy has but little effect on either the primary growth or the secondary
deposits. Sarcomas are often susceptible to anticancer drugs, but fibrosarcomas
are more resistant than other types. Sarcoma of bone is sensitive to
radiotherapy, which is used in some cases as an alternative to amputation
(Chapter 25).
Lymphomas
Lymphomas arise in lymph nodes, tonsils, Peyer’s patches or lymph
nodules in the intestines. Lymph nodes of the neck or mediastinum are most
commonly affected (Chapter 17). They have a bad prognosis.
Synovioma
This rather uncommon tumour may arise in any synovial joint or tendon
sheath, especially those of the hand. It appears as a soft, painless swelling,
and sarcomatous changes can occur. The diagnosis can only be established by
excision and biopsy of the tumour.
Naevus and melanoma are described in Chapter 13.
Endothelioma;
mesothelioma
The endothelial linings of blood vessels, lymphatic spaces and serous
membranes occasionally give rise to neoplasms. They can be malignant. They arise
from the pleura (Chapter 47) and rarely from the pericardium or peritoneum.
Asbestos inhalation may provoke their development. ‘Blue’ asbestos fibres
especially have been shown to be a cause. The original cells are flattened, but
they become spheroidal or cuboidal when neop]astic changes occur. The
‘endothelioma’ (meningioma) of the dura mater is thought to arise from the
arachnoid membrane, which is not an endothelial structure (Chapter 35).
Peritheliomas are tumours arising in the endothelial lining of small
blood vessels or lymphatics. Carotid body tumours are probably of this nature
(Chapter 43).