Question: The pathologist diagnosed a specimen as a pineocytoma. Which ICD-10 code should I report? Rhode Island Subscriber Answer: A pineocytoma is a benign tumor of the pineal gland. You should report the diagnosis as D35.4 (Benign neoplasm of pineal gland). Pineal gland: The pineal gland, or pineal body, is a small endocrine gland located between the two cerebral hemispheres. The is responsible for melatonin production, which plays an important role in circadian rhythms and sleep.