We describe a patient with diffuse large B-cell lymphoma metastasizing to the anterior pituitary, in whom pituitary function was restored after successful treatment of the lymphoma. An early report of complete resolution of non Hodgkin's lymphoma involving the pituitary was based on 67gallium scintigraphy and the patient remained on hormone replacement . More recently, partial recovery of anterior hypopituitarism was reported after successful chemotherapy but the patient continued to require thyroxine . Complete and persistent pituitary recovery as in this case report is very rare.
Consistent with previous case reports [5, 6], diffuse large B-cell lymphomas are the commonest types of lymphoma to involve the pituitary or central nervous system. Primary pituitary lymphoma is exceedingly rare. They usually present with headache, cranial nerve abnormality and evidence of pituitary insufficiency . By contrast, pituitary metastasis may be asymptomatic presumably because of the pituitary's large reserve capacity. When symptomatic, posterior lobe involvement is more common, but isolated anterior pituitary dysfunction was present in six of a series of 13 patients previously reported .
Typically, MRI reveals a pituitary mass which on T1- and T2-weighted images is either iso- or hypodense and enhances with contrast . Unlike other brain tumors, T2-prolongation is not present owing to the dense cellularity and high nucleus to cytoplasm ratio of lymphoma . In patients with posterior pituitary involvement, there is typically absence of the pituitary bright spot. In our patient, the pituitary magnetic resonance image was normal, which we presume indicates a diffuse infiltration by lymphoma cells rather akin to a hypophysitis with infiltrating lymphocytes.
Differential diagnosis of a pituitary mass has been well described previously . In a patient with a normal pituitary image and anterior hypopituitarism, the differential includes other infiltrative processes including sarcoidosis and hypophysitis.
Our patient was not subjected to a pituitary biopsy as we felt we had sufficient evidence of lymphomatous infiltration of the pituitary based on clinical findings, histology from liver and lymph nodes and PET scan results. Pituitary lymphomas are described as firm, vascular and adherent to surrounding structures and needing piecemeal dissection. This is in contrast to necrotic adenomas which are typically soft . In our patient, the simultaneous improvement in pituitary function with tumor response to chemotherapy was also highly suggestive.
Prognosis in previous reported series ranges between nine weeks after presentation to greater than 20 years . Prognostic factors include age, comorbidity and histology at presentation. However widespread lymphoma, as in our patient, is not, in itself, indicative of poor prognosis.