A patient presents with unilateral pelvic pain and an adnexal mass. What is the most likely diagnosis for a cystic mass on the right ovary?

In the context of a patient presenting with unilateral pelvic pain and an adnexal mass, the identification of a cystic mass on the right ovary can lead to several potential diagnoses. A follicular cyst is typically a physiological cyst that develops from a follicle which fails to rupture during the menstrual cycle, leading to continued fluid accumulation. These cysts are commonly encountered in women of reproductive age and are often asymptomatic, but can occasionally manifest with unilateral pelvic pain when they grow large enough to cause discomfort or when they rupture.

Follicular cysts are typically anechoic on ultrasound, meaning they appear dark and fluid-filled; this clarity helps differentiate them from other types of cysts. Given these characteristics and the context of the patient's symptoms, the diagnosis of a follicular cyst becomes the most plausible explanation for the cystic mass in this scenario.

Other types of cysts, such as corpus luteal cysts, dermoid cysts, or endometriomas, have distinct features and clinical presentations that differ from those of a simple follicular cyst. For example, corpus luteal cysts often present with more complex echogenicity due to the presence of blood products and can be associated with menstrual irregularities. Dermoid cysts contain various