© Springer International Publishing AG 2018
Keith A. Delman and Viraj A. Master (eds.)Malignancies of the Groinhttps://doi.org/10.1007/978-3-319-60858-7_22. Epidemiology of Diseases of the Groin
(1)
Division of Surgical Oncology, Department of Surgery, Emory University School of Medicine, 1365 Clifton Rd NE, Atlanta, GA 30322, USA
Keywords
GroinInguinalEpidemiologyIncidenceFrequencyMelanomaPenile cancerVulvar cancerExtremity soft tissue sarcomaAnal cancerIntroduction
The epidemiology of diseases of the groin varies rather markedly by the type of disease. Patients with melanoma tend to be younger than patients with nonmelanoma skin cancers and than those with squamous cell carcinomas of the penis and vulva. UV exposure predisposes to melanoma and nonmelanoma skin cancers, while HPV infection and tobacco use are associated with squamous cell carcinomas of the vulva and penis. Management of cancers that affect the groin depends on the type of cancer, but surgery remains the best chance for cure in almost cases, with anal squamous cell carcinoma being the exception. This chapter introduces the comparative epidemiology of diseases of the groin in an effort to provide context for treatment algorithms for each of the specific disease processes.
Melanoma
Melanoma accounts for less than 5% of all skin cancers but has the highest mortality. It is estimated to be the fifth most common cancer in males and seventh most common cancer in females. A total of 87,110 new cases of melanoma and 9730 deaths from melanoma are estimated in the United States in 2017 [1]. The incidence of melanoma has been steadily increasing over the past several decades with an annual increase varying between 3 and 7% [2]. This is thought to be related to changing behaviors regarding sun exposure and increased detection of early lesions [3]. While the incidence of melanoma has consistently increased, in general mortality rates have stabilized given the trend toward more frequent diagnosis of early-stage melanomas that are more likely to be curable.
There is however marked variability in mortality rates based on age. Older patients tend to have more aggressive primary tumors that are more often on the head and neck; these patients have higher mortality rates compared with other age groups [4]. In addition, according to SEER data, mortality rates continue to decrease for patients 20–44 years old but continue to increase for patients older than 65 [5].
Overall incidence of and mortality from melanoma are higher in men than in women. Of the estimated melanoma cases in 2017, 59.9% are expected to be diagnosed in males, and 65.5% of patients that die from melanoma will be males [1]. In patients aged 18–39 years, women have had a significantly higher increase in incidence of melanoma compared to males of the same age. Males more commonly develop melanomas on the head and neck whereas females are more likely to have extremity or trunk melanomas.
Melanoma is essentially a disease of Caucasians, who account for 95% of new melanoma diagnoses. African Americans are the next most commonly affected group, accounting for approximately 0.5% of cases. Non-Caucasians are more likely to present with advanced-stage disease and tend to have worse overall survival compared to Caucasians [6]. The lifetime risk of developing melanoma is 2.5% for Caucasians, 0.1% for Blacks, and 0.5% for Hispanics.
Risk factors contributing to the development of melanoma include ultraviolet light exposure, personal or family history of melanoma, fair complexion, immunocompromised states, advanced age, male sex, congenital melanocytic nevus, and familial melanoma syndromes such as dysplastic nevus syndrome. People with any of these risk factors are advised to undergo routine dermatologic exams and self-skin exams and practice safe sun exposure habits.
Nonmelanoma Skin Cancer
Squamous Cell Carcinoma
While it is difficult to assess the total number of cases of nonmelanoma skin cancers given the lack of population-based registries, it is estimated that over five million basal and squamous cell carcinomas are diagnosed each year. Of these, approximately two in ten are squamous cell carcinomas, which we will focus on here given their greater propensity to be more aggressive than basal cell carcinomas. The overwhelming majority of squamous cell carcinomas (approximately 80%) develop in the head and neck. This is likely related to UV light exposure, which is one of the strongest risk factors for the development of nonmelanoma skin cancers. Other risk factors include previous radiation exposure, actinic keratoses, immunosuppression, previous scars or burns, and disorders such as xeroderma pigmentosum, epidermolysis bullosa, and pansclerotic morphea of childhood.
Given that most patients with cutaneous squamous cell carcinoma present with primaries on the head and neck, there is little data about the frequency and management of inguinal lymph node involvement from perineal or lower extremity primaries. Lymph node metastasis is often associated with adverse pathologic findings such as lymphovascular invasion, poor differentiation, and perineural invasion. High-risk lesions, defined as primaries greater than 2 cm on the extremities with adverse pathologic findings or in the setting of immunosuppression, tend to have higher rates of lymph node and distant metastases. Patients with nodal metastases have expected 10-year survival of less than 20% [7]. In general, rates of nodal involvement are low, but early detection and treatment may significantly alter the prognosis of patients with lymph node metastases.
Merkel Cell Carcinoma
Merkel cell carcinoma (MCC ) is a rare neuroendocrine cancer of the skin with a historically poor prognosis. It is one of the least common types of skin cancer, with an estimated 1500 case diagnoses per year. MCC is essentially a disease of older whites, with two-thirds of patients over the age of 70 and nine out of ten patients being white. Risk factors include extensive sun exposure, older age, and immunosuppression. Immunosuppressed patients that develop MCC tend to be much younger (approximately 50% younger than 50 years old) than immunocompetent patients with MCC. A novel polyomavirus has been identified in a majority of cases of MCC, but a causal link between this virus and the development of MCC has not been established [8].
Approximately 15% of patients with MCC present with primary lesions on the lower extremity and 27% present with lymph node involvement [9]. Nodal involvement is associated with a decrease in 5-year survival from 64% with local disease to approximately 39%. Nodal disease is detected in the sentinel lymph node in approximately one-third of patients without clinically detectable lymph node metastasis. Patients with pathologically negative sentinel lymph nodes appear to have a survival advantage compared to patients that undergo only clinical nodal evaluation, which confirms the utility of sentinel lymph node biopsy.
Penile Cancer
Squamous cell carcinoma (SCC) represents the most common type of cancer of the penis but is rare, representing only 0.5% of malignancies in men. There will be an estimated 2120 new cases of and 360 deaths from penile SCC in 2017 in the United States [1]. The incidence is significantly higher in men in developing countries, particularly Asia and Africa.
Median age at diagnosis in the United States is 68 years. Risk factors for the development of penile SCC are phimosis, balanitis, penile trauma, tobacco use, lichen sclerosus, poor hygiene, and a history of sexually transmitted disease, particularly human papillomavirus (HPV) [10]. Up to 80% of penile SCC is related to HPV ; HPV types 16 and 18 are strongly correlated with the development of penile SCC [11]. Patients with HIV are also at significantly increased risk of developing penile cancer, although this increased risk may be related to increased incidence of HPV among males with HIV. The protective effects of neonatal circumcision against penile SCC are thought to be lost in adults that undergo circumcision. This is likely related to the elimination of phimosis and lower incidence of HPV infections in neonates undergoing circumcision compared to adults [12].