Double adenomas of the pituitary: an imaging, pathological, and clinical diagnostic challenge
Double and multiple adenomas of the pituitary are composed of two or more distinct tumors located in the same gland. They represent uncommon lesions measuring less than 1 cm, reported as having a low incidence in autopsies and occurring even more infrequently in surgical series. The histological diagnosis of double adenomas in surgical material is often extremely difficult, and confirmation requires immunohistochemistry and, occasionally, electron microscopy. Fragmented tissue material submitted for histology after transsphenoidal resection complicates the diagnosis. Difficulties in demonstrating double or multiple adenomas by imaging techniques contribute to diagnostic failure. Magnetic resonance imaging (MRI) techniques may disclose two separate adenomas located in the same pituitary gland. Intraoperative MRI and imaging ultrasonography, together with positron emission computed tomography, more accurately identify sites of residual tumors. These techniques might also detect postoperatively a residual tumor belonging to the second component of double adenoma. Double adenomas may also create extreme clinical diagnostic challenges. It is almost impossible to suspect functioning double adenomas with combined hormone secretion, each one secreting a different hormone, and distinguish them from an isolated plurihormonal adenoma, simultaneously secreting more than one hormone. Double adenomas may underlie surgical failure when one adenoma is removed while the other is left behind. Despite the low frequency of double adenomas, identification and resection of both of them is of major importance for the achievement of biochemical cure.
KeywordsDouble adenomas Multiple adenomas Histology Hormones Imaging techniques Immunohistochemistry Pituitary
Double adenomas of the pituitary, which are composed of two clearly distinct tumors located in the same gland, occur infrequently. Multiple adenomas, which consist of more than two tumors [1, 2], may coexist with other sellar neoplasms or tumor-like lesions [3, 4]. To the best of our knowledge, a single case of pituitary adenoma coexisting with ectopic adenoma located in the pituitary stalk has been reported . In most instances, double adenomas are simultaneously diagnosed, while asynchronous development is rare [1, 2, 6]. As a rule, double adenomas are microadenomas measuring less than 1 cm. The first series of multiple adenomas reported 44 tumors in an autopsy material (16 double and 4 triple), while the first surgical series of double adenomas included another 11 tumors [1, 2]. According to a recent review, 63 patients with 129 adenomas, including 60 double and three triple were reported . For the first time, a short chapter dedicated to double adenomas of the pituitary was included in the recent edition of the World Health Organization (WHO) classification of tumors of endocrine organs .
The incidence of double adenomas is very low, ranging from 0.4 to 1.3% in surgical material and 0.9 to 0.9% in autopsy series [1, 2, 9, 10]. Their lower frequency in surgical series is attributed to several reasons. Recognition in routine hematoxylin-eosin histological sections is often difficult or impossible, unless they are composed of two different cell types. Transsphenoidally removed adenomas submitted in small fragments for histology make diagnosis extremely complex. It is impossible to separate double adenomas with the same immunoprofile on histology grounds . In addition, due to selective adenoma resection, the residual adenohypophysial parenchyma remains unexplored. Lastly, aspiration during transsphenoidal surgery results in partial loss of the adenoma tissue. While multiple adenomas are incidentally found in autopsies, their detection in surgical material is exceptional [1, 7, 11], since, as a rule, they are of small size and hormonally nonfunctional . Given that, in autopsies, the whole pituitary gland is available for evaluation, the geographic distribution of multiple adenomas permits easy identification, even of tumors composed of the same cell type. In addition, clear demarcation of the adenoma, compression of the adjacent adenohypophysial parenchyma, and condensation of the surrounding reticulin fiber network allow precise identification of even tiny adenomas. Nevertheless, the higher incidence of multiple adenomas in autopsy material suggests that many of these lesions remain undiagnosed, particularly when they are clinically nonfunctioning.
The etiology of double and multiple adenomas remains uncertain. They might originate from the incidental occurrence of two monoclonal components belonging to two different cytogenetic lineages. Alternatively, they may represent two different lesions deriving from clonal expansion of uncommitted stem cells that have undergone multidirectional differentiation [2, 12]. Immunohistochemistry for transcription factors (Pit-1, Tpit, and SF-1) confirms the divergent lineages of cytodifferentiation in double adenomas . However, according to the recent WHO classification of endocrine tumors, application of transcription factors can be complementary and is not recommended for routine diagnosis . Double adenomas are in their substantial majority sporadic neoplasms, occasionally associated with multiple endocrine neoplasia type-1 [14, 15].
Difficulties in demonstrating super numerical adenomas by imaging techniques may result in diagnostic failure. CT scan and MRI can identify microadenomas of 2–3 mm with a sensitivity of 60 and 85%, respectively . High-resolution MRI techniques may disclose two separate adenomas in the same pituitary gland [9, 14, 17, 18]. It is more difficult to detect a residual pituitary adenoma after transsphenoidal surgery. Postoperative imaging using conventional MRI may only occasionally distinguish residual tumor from normal anterior pituitary parenchyma . Intraoperative MRI (iMRI), combined with synchronous direct inspection of the sellar or suprasellar areas during the surgical procedure, facilitates detection and removal of residual tumor. However, this method is less sensitive when the tumor remnants are smaller than 3 mm . Furthermore, intraoperative pituitary imaging ultrasonography (iUS) may identify and allow targeted resection of small hyperechoic pituitary tumors, even in MRI-negative cases, as is typical in Cushing’s disease . Lastly, functional imaging using 11C-methionine positron emission tomography, co-registered with 3D gradient echo MRI (Met-PET/MRI), can recognize sites of residual hormone active adenoma in acromegaly patients operated on via transsphenoidal surgery . All these novel techniques might also detect the second component belonging to a double adenoma left behind in the initial operation.
Functioning double adenomas of the pituitary are associated with endocrine symptoms due to hormonal excess by one or both of them [2, 23]. There is no general agreement regarding the relevance of functioning somatotroph and corticotroph adenomas among double adenomas in surgical material [7, 8]. Several studies have reported a higher frequency in acromegaly patients, followed by those presented with Cushing’s disease [2, 8, 24]. A recent review of the literature, based on a cohort of 63 patients harboring double adenomas, reported a slight numerical difference between acromegaly and Cushing’s patients. Twenty-four of them were diagnosed in patients presenting with Cushing’s disease and 22 in subjects with acromegaly . The discrepancy with earlier studies is attributed to the inclusion of a publication by experts in Cushing’s disease. In this study, the authors focused on assessing the incidence of multiple pituitary adenomas only in patients harboring Cushing’s disease . A more recent review analyzed truly separate double or multiple pituitary adenomas identified preoperatively by MRI and confirmed by histology and immunohistochemistry. Among these 17 cases published between 1975 and 2016, the authors report a higher frequency of growth hormone (GH)-secreting adenomas, followed by corticotropin hormone (ACTH)-secreting adenomas. In addition, the patients’ age ranged from 22 to 67 years, with a higher preponderance in females . The overall reported incidence in patients with double adenomas associated with Cushing’s is 1.6–3.3% [9, 14, 26]. Corticotroph adenomas found in double lesions may coexist with corticotroph cell hyperplasia, rarely proceeding to adenoma transformation [27, 28]. Corticotroph adenomas, among double tumors in surgical material, may also present as silent [1, 7, 9, 25]. Functioning adenomas producing other hormones often coexist with nonfunctioning tumors [1, 2, 7, 29]. The latter, among double adenomas, are diagnosed either on the basis of mass effect symptoms or incidentally . In autopsies, silent lactotroph adenomas are the most frequent among multiple adenomas, followed by silent corticotroph, silent somatotroph, and gonadotroph adenomas [1, 7]. The latter showing focal immunopositive for luteinized or/and follicle-stimulating hormone or/and α-glycoprotein hormone subunit were previously diagnosed as null cell tumors or oncocytomas [1, 30].
Coexistence of double adenomas in the same pituitary gland also creates extreme clinical diagnostic difficulties. Surgical resection of the nonfunctioning adenoma rather than the functioning one in double adenomas leads to a poor clinical outcome [2, 23]. It is almost impossible to suspect functioning double adenomas independently producing distinct pituitary hormones [2, 23, 27]. In such a case, double adenomas may underlie surgical failure when one adenoma is removed while the other is left behind. Hyperprolactinemia in acromegaly patients further complicates the diagnosis raising the question whether it is a result of pituitary stalk compression or it is due to separate secretion of GH and PRL by two independent somatotroph and lactotroph adenomas respectively. A typical example illustrating this issue has been published describing a patient with acromegaly and galactorrhea-amenorrhea caused by two separate adenomas, one producing GH and the other PRL . Other reports exemplify patients with Cushing’s disease harboring double adenomas, in whom the neurosurgeon removed only the GH- or a PRL-secreting tumor, while resection of the residual functioning corticotroph adenoma was performed in a second operation [9, 27]. Therefore, continuing endocrine symptoms after pituitary surgery are highly suspicious for the implication of double adenomas.
In summary, identification of double adenomas is of utmost importance to make a correct diagnosis and to correlate the patient’s clinical presentation with the type of hormone product, thus avoiding a second surgery. Imaging techniques should always be carefully applied in order to achieve identification of the presence of double adenomas, meticulous surgical pituitary exploration being particularly important in patients with Cushing’s disease or acromegaly. However, a definitive diagnosis of double adenomas should be assessed exclusively upon pathological evaluation. It must be stressed that, despite the low frequency of double adenomas, it is of major clinical importance to identify and remove both tumors in one step so as to achieve biochemical cure.
Compliance with ethical standards
Conflict of interest
All authors declare that they have no conflict of interest.
- 5.Mendola M, Dolci A, Piscopello L, Tomei G, Bauer D, Corbetta S, Ambrosi B (2014) Rare case of Cushing’s disease due to double ACTH-producing adenomas, one located in the pituitary gland and one into the stalk. Hormones 13(4):574–578. https://doi.org/10.14310/horm.2002.1503 CrossRefPubMedGoogle Scholar
- 8.Kontogeorgos G, Kovacs K, Lloyd RV, Righi A (2017) Plurihormonal and double adenomas. In: Lloyd RV, Osamura RY, Klöppel G, Rosai J (eds) WHO classification of tumours of endocrine organs, 4th end. IACR, Lyon pp 39–40Google Scholar
- 13.Osamura RY, Grossman A, Korbonits M, Kovacs K, Lopes BMS, Masturo A, Troullas J (2017) Pituitary adenoma. In: Lloyd RV, Osamura RY, Klöppel G, Rosai J (eds) WHO classification of tumours of endocrine organs, 4th end. IACR, Lyon pp 14-18Google Scholar
- 16.Johnsen DE, Woodruff WW, Allen IS, Cera PJ, Funkhouser GR, Coleman LL (1991) MR imaging of the sellar and juxtasellar regions. Radiographics 11(5):727–758. https://doi.org/10.1148/radiographics.11.5.1947311 CrossRefPubMedGoogle Scholar
- 19.Kremer P, Forsting M, Ranaei G, Wüster C, Hamer J, Sartor K, Kunze S (2002) Magnetic resonance imaging after transsphenoidal surgery of clinically non-functional pituitary macroadenomas and its impact on detecting residual adenoma. Acta Neurochir 144(5):433–443. https://doi.org/10.1007/s007010200064 CrossRefPubMedGoogle Scholar
- 30.Kontogeorgos G, Thodou E (2016) The gonadotroph origin of null cell adenomas. Hormones 15(2):243–247. https://doi.org/10.14310/horm.2002.1652