**Core Concept**
The patient's symptoms of pulsatile tinnitus and hearing loss, along with a visible vascular mass behind the tympanic membrane, suggest a vascular anomaly affecting the middle ear. This condition is characterized by abnormal connections between the high-pressure arterial system and the low-pressure venous system, leading to turbulent blood flow and subsequent symptoms.

**Why the Correct Answer is Right**
The correct diagnosis is a glomus tympanicum tumor, a type of paraganglioma that arises from the glomus body in the middle ear. This tumor is composed of neuroendocrine cells that produce catecholamines, leading to increased blood flow and subsequent symptoms. The presence of a vascular mass behind the tympanic membrane, along with the patient's symptoms, is highly suggestive of this diagnosis.

**Why Each Wrong Option is Incorrect**
**Option A:** Lymphoma is not typically associated with pulsatile tinnitus or a visible vascular mass behind the tympanic membrane. Lymphoma can cause hearing loss, but it would not present with these specific findings.
**Option B:** Meningioma is a type of brain tumor that can cause hearing loss, but it would not present with a visible vascular mass behind the tympanic membrane. Meningioma is also not typically associated with pulsatile tinnitus.
**Option C:** Otosclerosis is a type of bone growth in the middle ear that can cause hearing loss, but it would not present with a visible vascular mass behind the tympanic membrane. Otosclerosis is also not typically associated with pulsatile tinnitus.

**Clinical Pearl / High-Yield Fact**
Glomus tympanicum tumors are rare, but they are highly suggestive of pulsatile tinnitus and hearing loss when a vascular mass is seen behind the tympanic membrane. These tumors are often treated with surgical excision, and early diagnosis is critical to prevent further complications.

**Correct Answer:** D. Glomus tympanicum tumor.