Pituicytoma
In 2017, changes in the classification of non-neuroendocrine tumors are also proposed, in particular those tumors arising in the posterior pituitary including pituicytoma 1).
Pituicytoma is a rare glial sellar/suprasellar neoplasm arising in the neurohypophysis with a possible origin from the folliculostellate cells of the adenohypophysis which are non-endocrine spindled cells expressing S-100 and Bcl-2 2) 3).
Pituicytoma is considered to be a distinct Grade I neoplasm 4).
Although usually intra-sellar, pituicytomas can have suprasellar extension; however, purely suprasellar examples although rare have been reported 5).
Epidemiology
PTs had a higher prevalence in the fifth and sixth decades of life, with a slight male predominance. 6). 7)
Clinical features
The presenting symptoms are due to the mass effect of the tumor and include visual disturbances caused by direct compression on the optic chiasm, headaches, endocrinological symptoms and rarely diabetes insipidus 8).
Diagnosis
Subtypes
TTF-1 Expressing Sellar Neoplasm with Ependymal Rosettes and Oncocytic Change: Mixed Ependymal and Oncocytic Variant 9).
Differential Diagnosis
When small, and clearly localized to the infundibulum the main differential includes:
granular cell tumors of the pituitary region
craniopharyngioma
When larger, then it is difficult to anticipate the diagnosis with other diagnoses being far more common, including:
pituitary macroadenoma
meningioma
pituitary metastasis
pituitary infiltration
lymphocytic hypophysitis
neurosarcoidosis
optic pathway glioma
Absent Rosenthal fibers and eosinophilic granular bodies, usually help to distinguish between pituicytomas and pilocytic astrocytomas 10).
Amongst the various sellar tumors, pituicytoma and spindle cell oncocytoma (SCO) have considerable overlap in histological, Immunohistochemical (IHC) profile and can have extensive intraoperative bleeding making complete excision difficult with increased chances of recurrence. It is important to differentiate pituicytoma from SCO since the former is associated with a slightly better prognosis with recurrence being uncommon after complete surgical excision. Till 2013, out of 29 cases of pituicytoma with a detailed follow-up, recurrence was seen in six cases, all of which were found to have an incomplete resection during the first surgery 11).
SCO on the other hand have a tendency to recur even after complete excision. Hence, it is advocated to combine surgery with adjuvant radiotherapy in all cases of SCO to reduce the chances of recurrence. EMA is strongly positive in SCO, thus it can help to differentiate pituicytoma from SCO 12).
Treatment
Review
Less than 50 cases have been reported in the world literature till 2013 13).
Salge-Arrieta et al., from the Ramón y Cajal University Hospital Madrid, Spain, published a retrospective review of case reports published in the scientific literature to 2018, including a new illustrative example treated.
116 cases were collected. PTs had a higher prevalence in the fifth and sixth decades of life, with a slight male predominance. Main symptoms, which tended to be progressive, included visual field defects and pituitary-hypothalamic dysfunction. Radiologically, PTs were found anywhere along the hypothalamic-pituitary axis mimicking other, more frequent tumors growing in this anatomical region. Surgical treatment included both transcranial or transsphenoidal approaches, and resulted in gross total resection and morbidity rates of 46.8 and 59%, respectively; the latter essentially consisted in anterior and posterior pituitary dysfunction, with limited impact on daily quality of life.
Due to both low frequency and the absence of pathognomonic clinical and/or radiological features, formulating a suspicion diagnosis of PT represents a considerable challenge even for experienced professionals. The indication for treatment should be made on an individual basis, but it is inescapable in the presence of a visual field defect. The surgical approach has to be tailored according to the topography of the tumor and preoperative symptoms; the greatest challenges in accomplishing a gross total removal are represented by the degree of adherence and vascularization of the PT 14).