Final answer:
The likely diagnosis for the 17-year-old boy with a painless neck mass, weight loss, and night sweats is Hodgkin's lymphoma, especially considering the typical presentation and age group.
Step-by-step explanation:
The symptoms described in the case, such as a painless growing neck mass, significant weight loss, and night sweats, are hallmark features of lymphoma. The rubbery consistency and the location of the mass in the anterior cervical triangle are further suggestive of this diagnosis. Hodgkin's lymphoma, in particular, is known for presenting with a rubbery and mobile lymph node mass. The overlying skin being intact, with no signs of infection, such as redness or drainage, makes a localized infection less likely and points toward a systemic process like lymphoma.
While other types of lymphoma, such as Burkitt lymphoma, non-Hodgkin's lymphoma, and T-cell lymphoma, could potentially present with similar symptoms, Hodgkin's lymphoma is classically associated with the symptoms described and is more common in the age group of this patient. A definite diagnosis would require a biopsy of the lymph node to confirm the presence of characteristic Reed-Sternberg cells diagnostic for Hodgkin's lymphoma.