ADVANCED CARCINOMA
OF THE PENIS
Practically all penile cancers are squamous
carcinomas. Initially, there is thickening of the glans penis or preputial
epithelium, with epithelial pearl formation, central degeneration, and
keratinization. Penile cancers may be papillary and exophytic or flat and
ulcerative. Cancer cells then penetrate the epithelial basal layers, extend to
subcutaneous tissue, and subsequently to lymphatics. If untreated, penile
autoamputation can occur.
Penile cancer is rare but deadly, with an estimated
1300 new U.S. cases annually (< 1% of cancers). One reason for the high mortality
rate is that patients tend to delay seeking medical attention, with 15% to 50%
delaying for more than 1 year from first awareness. Risk factors for penile
cancer include lack of circumcision, poor penile hygiene, phimosis, age >60
years, multiple sexual partners, and tobacco use. In addition, human papilloma-virus
(HPV) infection may increase the risk of penile cancer, because half of all
penile cancers are associated with HPV type 16 viral infection. Retained,
decom- posing smegma, together with balanoposthitis, may contribute to the
initiation of malignancy and explains why adult circumcision does not protect
against cancer. Penile cancer usually grows gradually and laterally along the
surface of the penis. Buck fascia (see Plate 2-3) acts as a temporary
barrier to corporeal invasion. Eventually, the cancer penetrates Buck fascia
and the tunica albuginea, after which systemic spread is possible. Penile
cancer metastasizes almost solely through the lymphatics, although occasionally
hematogenous spread through the dorsal vein of the penis occurs with spread to
the axial skeleton. Usually, the tumor metastasizes first to superficial inguinal
lymph nodes (see Plate 2-9), but the central,
presymphyseal lymph node and external iliac nodes may also be involved. Because
the lymphatics of the penile shaft intercommunicate, metastases may occur
bilaterally despite a unilaterally located primary lesion. The superficial
inguinal nodes drain to the deep inguinal nodes beneath the fascia lata. From
here, drainage is to the pelvic nodes. Inguinal lymph nodes extensively
involved with tumor may erode through the skin and into the femoral artery and
vein (see Plate 2-9). While penile cancer can be suspected from its
appearance, the diagnosis is established through biopsy of the primary lesion
or lymph nodes. Surgical excision constitutes definitive management of this
condition. If the tumor is less than 2 cm in size and confined to the prepuce,
circumcision may be sufficient. In small (<1.5 cm) glans lesions, Mohs micrographic surgery or
laser ablation may spare the penis and eradicate tumor; however local failure
is far more common after organ-sparing procedures. Partial penile shaft
amputation is appropriate when the cancer involves the glans and distal shaft.
A 2-cm margin is necessary; attempts to limit the resection can result in
recurrent tumor. If surgical resection with partial penectomy does not provide
an adequate margin, a total penectomy is considered along with a perineal urethrostomy.
Following treatment of the primary tumor, management of the inguinal lymph
nodes follows. The decision to resect inguinal nodes in patients with no
evidence of adenopathy, either clinically or after imaging studies, is
controversial. The incidence of occult metastases in patients without palpable adenopathy
is 20% to 25%. In addition, radical inguinal lymphadenectomy has a high
complication rate (80% to 90%) that includes serous lymphocele formation, wound
necrosis and infection, chronic leg edema, phlebitis, and pulmonary embolism.
Therefore,
modifications to this procedure, including limited, superficial lymph node
excision and sentinel lymph node biopsy (in which lymphoscintigraphy and
intradermal blue dye is injected around the tumor and examined for its presence
in the superficial inguinal lymph nodes to determine primary landing sites for
cancer), have become popular to reduce the need for, and complications from,
radical lymphadenectomy.
The
indications for pelvic lymphadenectomy have not been clearly delineated without
evidence of enlarged nodes
on imaging. When two or more inguinal nodes contain cancer, the probability of
pelvic node involvement is high and pelvic lymphadenectomy is indicated.
Patients with negative inguinal lymph nodes rarely have pelvic node
involvement. Regarding mortality, untreated patients with inguinal metastases
rarely survive 2 years. Those with clinically palpable adenopathy and proven
metastases have a 20% to 50% survival rate 5 years after definitive surgical treatment.
