SUN-068 - A Rare Case of Pituitary Carcinoma with Lumbar Spine Metastasis Treated with Cabergoline

Background:

Pituitary carcinoma is defined when a pituitary tumor metastasizes in distant locations. It is an exceedingly rare entity, accounting for approximately 0.1% of all pituitary tumors. Diagnosis is often challenging, leading to delays in recognition that may negatively impact outcomes, which remain historically poor.

We present a case of pituitary carcinoma occurring nearly two decades after the initial diagnosis of a pituitary adenoma. This case highlights the indolent yet aggressive potential of these tumors, the diagnostic challenges, and the role of cabergoline in achieving biochemical disease control.

Clinical

Case:

A 69-year-old man was initially diagnosed at age 40 with a large prolactin-secreting pituitary adenoma measuring 4.9 cm, associated with markedly elevated prolactin levels (~8,000 ng/mL). Initial treatment with bromocriptine was discontinued after one year because of intolerance, after which the patient was lost to follow-up.

At age 47, he represented with worsening headaches, prompting reevaluation that demonstrated interval tumor enlargement to 6.3 cm. Cabergoline therapy was reinitiated, followed by transsphenoidal debulking and craniotomy for suprasellar extension and subsequently adjuvant radiation therapy. He was again lost to follow-up.

At age 69, the patient presented with acute low back pain radiating to the right leg. Lumbar spine MRI revealed an enlarging intradural mass. He underwent L3–L5 laminectomies with tumor resection, and pathology confirmed pituitary neuroendocrine tumor drop metastasis. Concurrent pituitary MRI demonstrated interval enlargement of a 6-mm enhancing focus in the suprasellar cistern compared with prior postoperative imaging. Serum prolactin was elevated at 479 ng/mL, with associated hypogonadism, while other pituitary hormone axes were intact.

Cabergoline was initiated at a dose of 0.25 mg twice weekly, resulting in normalization of prolactin levels to 17 ng/mL after three months of therapy. Follow-up MRI revealed stable pituitary disease and decreased nodular size at the prior lumbar resection site. The patient undergoes close radiographic surveillance every two months during the first year. Should he develop resistance to cabergoline, treatment with temozolomide and radiation may be initiated.

Conclusion:

Significant uncertainties remain regarding the optimal management of pituitary carcinoma. Owing to its extreme rarity, the feasibility of large-scale randomized clinical trials is limited, and current treatment strategies are therefore largely informed by case reports and small case series. In our case, disease progression has been effectively controlled with cabergoline, although the durability of this response remains uncertain.

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