Page 189 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

168 PART III Therapeutic Modalities for the Cancer Patient

4. Tumors should be handled gently to avoid the risk of seed- recommended (en bloc resection). Limb amputation for exci-
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ing tumor cells into the surgical wound. Copious lavage of all sion of a malignant digit tumor with metastasis to the popliteal
LN and mastectomy procedures that include the regional LN
cancer wound beds helps mechanically remove small numbers
VetBooks.ir of exfoliated tumor cells; however, it should not replace gentle are examples of en bloc resections. Few other anatomic sites
tissue handling and the careful technique required to avoid
are amenable to this approach. Lymphadenectomy can have
entering the tumor bed. a beneficial effect on survival with specific tumor types, such
5. If more than one malignant mass is being removed, separate as dogs with apocrine gland anal sac adenocarcinomas (AGA-
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surgical packs should be used for each site to avoid iatrogenic SACs) metastatic to the sacral or sublumbar LNs, dogs with
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tumor cell implantation from one site to a second site. In addi- cutaneous mast cell tumors and LN metastasis, and cats with
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tion, gloves and instruments should be changed before closure mammary carcinoma and LN metastasis. Lymphadenectomy
to minimize the possibility of seeding of tumor cells in the inci- may also provide a palliative benefit for dogs with metastatic
sion. AGASAC LNs causing tenesmus.
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The aggressiveness of resection should be tempered only rarely 2. Normal-sized LNs can be metastatic. Normal-sized LNs that
by fears of wound closure. It is better to leave a wound partially or are known to drain a primary tumor site may be randomly
even in some cases completely open with no cancer cells than to sampled (biopsy or cytology) to gain further staging informa-
close it and have residual cancer. Numerous innovative reconstruc- tion. This is particularly important if adjuvant therapy deci-
tive techniques are available for closure of cancer wounds, and the sions (radiation therapy [RT] or chemotherapy) would be
surgeon is limited only by his or her ingenuity and willingness to predicated on confirmation of residual or metastatic cancer.
try new reconstructive techniques. Practice on a cadaveric speci- Intrathoracic or intraabdominal LNs are perhaps most crucial
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men is recommended before unfamiliar reconstructive surgical because they are not readily or safely accessible for histologic or
techniques are performed. Reliable microvascular-free composite cytologic examination (e.g., sublumbar LNs at the aortic tri-
transfers of muscle and skin are hampered because of the unique furcation), even under ultrasound guidance. In such cases the
canine skin and muscle anatomy, but they are being developed. 11 surgeon must educate the owner about the situation and either
remove the primary tumor without further knowledge of LN
Marginal Excision involvement or recommend removal of the normal-sized LNs
concurrently, for staging and possibly therapeutic purposes.
Aggressive surgical excision may not be recommended in some 3. LNs identified as sentinel LNs using various mapping proce-
cases because of the tumor’s type, size, and location; the patient’s dures (see Chapter 9 for more details).
age (i.e., recurrence with a less aggressive surgery may not be LN removal is generally not performed under the following
expected to occur within the expected life span of the patient); circumstances:
and other factors. In such cases marginal excision may be per- 1. LNs in critical areas (e.g., some mesenteric LNs) or in cases
formed (see Fig. 10.1D). The surgeon should tailor the level of in which the tumor cells have eroded through the capsule
excision to the needs of the patient and client, and the expecta- and become adherent (fixed) to surrounding tissues. In this
tions and goals of the procedure must be clearly established and scenario, LNs may not be resectable without leaving residual
explained to the client before surgery. disease in the wound bed (necessitating adjuvant therapy to
achieve local tumor control), or an attempt at removal may
Lymph Node Removal cause serious harm to the patient by injuring important adja-
cent structures. In such instances the prudent course usually is
Controversy surrounds the surgical management of regional LNs to aspirate or biopsy the LN for diagnostic purposes and leave
draining the primary tumor site. 12,13 As a general rule, epithelial it in situ, or to treat the LN with other modalities, such as RT.
cancers are more likely to metastasize to LNs than are mesenchy- 2. Prophylactic removal of normal LNs or chains of LNs is not
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mal cancers. However, any enlarged LN requires investigation for beneficial and may be harmful. Regional LNs may in fact be
complete staging. Lymphadenomegaly may develop secondary to the initiator of favorable local and systemic immune responses,
metastasis (firm, irregular, and sometimes fixed to surrounding and elective removal has been associated with poor survival in
tissue) or hyperplasia, or to reactivity to various tumor factors, certain human cancers. 12,19,20
infection, or inflammation. Metastasis is often a poor prognostic
sign, and a reactive LN may represent a beneficial host response. Surgery for Distant Disease
Enlarged LNs as a result of cancer metastasis and invasion are gen-
erally effaced by tumor cells; although these can often be diag- Metastasectomy for pulmonary metastasis has been described in
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nosed with FNA cytology, histopathology is superior to cytology dogs. Resection of liver metastasis for carcinomas (especially gas-
for the diagnosis of LN metastasis. LN extirpation should be trointestinal cancers) increasingly is being performed in human
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considered under a number of circumstances: oncology. As more effective adjuvant therapies evolve and mini-
1. If the LN is positive for cancer and not fixed to surrounding mally invasive techniques are further developed, the need for cyto-
normal tissues, it may be possible to remove it with some thera- reductive metastasectomy will likely increase.
peutic intent. Frequently, however, multiple LNs drain a pri-
mary tumor site (e.g., mandibular, medial retropharyngeal, and Palliative Surgery
parotid LNs for oral tumors), and lymphadenectomy is incom-
plete. LN metastasis at the time of initial diagnosis is often a Palliative surgery is an attempt to improve the quality of the
poor prognostic sign; however, patients that develop metastasis patient’s life (pain relief or improved function), but not necessarily
after local tumor control may benefit from lymphadenectomy. survival time. This type of surgery requires careful consideration
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Although it usually is not practical, removal of the primary of the expected morbidity of the procedure versus the expected
tumor, intervening lymphatic ducts, and draining LN has been gain for the patient and owner. In essence it comes down to a