Final Diagnosis -- Sellar Melanocytoma


Sellar Melanocytoma


Melanocytes in the CNS arise from the multipotential cells residing in the lateral parts of the neural crest. They appear on the 22th day of embryonal development and become part of the pia mater and the arachnoid mater of the cerebrum and spinal cord. They are present in the highest concentration in parts of the meninges lining the posterior cranial fossa near the pons, cerebellum, medulla oblongata as well as the cervical segment of the spinal cord explaining why primary melanocytic tumours of the CNS are most commonly seen in these locations. Less frequent structures to be affected include the spinal cord, the pineal body, Meckel's cavity, the pontocerebellar angle and the remaining structures of the skull base.

Among the primary melanocytic tumours of the CNS originally described by Hayward (7), the WHO classification distinguishes generalised forms (diffuse melanocytosis and neurocutaneous melanosis) and focal forms: melanocytoma and malignant melanoma, which differ in histologic features and malignant potential determining the clinical course and prognosis. Focal neoplasms form isolated, often encapsulated and usually black, brownish or bluish foci. Pigment-free tumours have also been reported (8). The microscopic appearance of melanocytoma, which is considered to be a benign tumour, is dominated by arrangements of melanocytes of high maturity that form nests, whorls or intertwining fascicules that locally form storiform (wheel-and-spokes) structures. The tumour cells are morphologically similar, of spindle-like or epithelioid nature, with high content of melanin in the cytoplasm. Only exceptionally, areas of necrosis or bleeding are seen. The mitotic index is usually low (MIB-1 0-1%). Malignant melanoma, on the other hand, is a high-grade tumour characterised by cellular polymorphism, presence of multinucleated giant cells of variable pigment content. Areas of necrosis, bleeds and infiltration of the neural tissue adjacent to the tumour are more commonly seen, and the proliferative activity of the cells is high (MIB 1 usually exceeds 3%). Brat et al. distinguished also intermediate-grade tumours, characterised by an elevated MIB-1 (1-4%) and traits of neural tissue infiltration despite benign histologic appearance of the tumour (2). There have also been reports of several cases of malignant transformation of the tumour (13, 15, 23, 25, 26) confirmed by histopathological examinations of specimens obtained during subsequent surgeries. The histopathological features that would allow to predict the course of the disease have not been established.

An overwhelming majority of melanocytic tumours of the CNS are malignant melanoma metastases. No radiological or histopathological criteria have been established to differentiate a primary tumour from a metastasis and a thorough search for a potential melanoma in other regions of the body is mandatory.

Melanocytic tumours of the CNS have a specific presentation on MRI associated with their high content of melanin. These include tumour hyperintensity in T1-weighted and FLAIR sequences and hypointensity in the T2-weighed images. The degree of concentration of melanin corresponds with the T1WI hyperintensity (11, 20). They undergo a homogenous contrast enhancement, however as they are hyperintense before contrast administration, their enhancement cannot always be assessed. Owing to their rarity they are routinely misdiagnosed, the most common diagnosis being a meningioma. This is also what happened in our case; radiological suspicion of an atypical meningioma was supported by the narrowing of the cavernous segment of the internal carotid artery and contrast enhancement of the dura mater lining the middle cranial fossa adjacent to the parasellar region. Another common diagnosis is a pituitary macroadenoma with signs of intratumour bleeding (1, 3, 27); the T1-hyperintensity could be explained by the presence of blood degradation products. The radiological presentation of the tumour was not suggestive of other diseases of this region which could match those MRI characteristics, e.g. a craniopharyngioma containing a calcification or a spindle cell oncocytoma.

Sakata underlined the importance of distinct angiographic features of a sellar melanocytoma (17). In their case, angiography clearly demonstrated hypervascularity of the tumor explaining the massive intraoperative bleeding unusual for a pituitary adenoma which was also encountered in our case. We did not however regard a preoperative angiography to be necessary.

The sella turcica and the optic chiasm area are an exceptional location of these rare tumours. There have been 16 reports of sellar melanocytic tumours, 8 of which were diagnosed as primary melanoma (1, 3, 5, 8, 12, 18, 19, 22), 7 as melanocytoma (4, 6, 16, 17, 21, 24, 27) (table 1); in one case the exact diagnosis was not précised (10). Clinical presentation is uncharacteristic and the symptoms are typically related to the compression of the surrounding structures by the tumour. The most common manifestation was deterioration of vision, visual field impairment and endocrine abnormalities (hyperprolactinemia and pituitary insufficiency) caused by compression of the stalk and the anterior lobe of the pituitary gland. Diplopia and eye pain resulting from infiltration of the cavernous sinus were less frequent. The treatment of choice is gross total removal of the tumour which allows to improve vision and the endocrine function of the pituitary. As regards efficiency of adjuvant treatment (radiotherapy), there is no clear proof of its utility (14). Radiotherapy was offered to 5 of the 8 reported patients including our case however the longest survival periods have been reported for the two patients who both underwent complete tumour removal and did not receive radiation (17, 27). This may show that radiation therapy does not offer any substantial benefits and surgery is the most valuable treatment for melanocytoma. There is also uncertainty concerning potential negative effects of radiation treatment on tumour behaviour and the incidence of malignant transformation. Owing to the rarity of these tumours and little data this problem, however, remains unsolved.

The efficacy of treatment of primary intrasellar melanocytic tumours is limited, with patients diagnosed of a melanocytoma faring much better than those with a primary melanoma. In case of the latter diagnosis survival period has rarely exceeded few years irrespectively of the extent of resection nor the use of adjuvant therapy (radiation and chemotherapy in one case (5)). The results of treatment of melanocytoma have been more favorable; the longest survival has exceeded for this moment 7 years in the case reported by Sakata (17). The most probable reason of relapse is incomplete tumour resection with its subsequent regrowth or malignant transformation. It is worth to underline, however, that in our case the results of histologic examination even at the second surgery just before the rapid expansion of the tumour were unanimously characteristic of a benign lesion. It could be still possible that the specimens might have not included the areas of maximum malignancy of the tumour which in turn could have been underestimated.

In conclusion, diagnosis of a melanocytoma or other melanocytic tumours should be taken into consideration in case of an unusual MRI appearance of a sellar mass (hyperintensity on T1 weighted images before contrast administration). As in surgery for pituitary adenoma, the extrasellar expansion of a melanocytoma is an important factor limiting the feasibility of its complete removal. Radiotherapy should probably be offered after incomplete tumour resection, however its benefits following total removal could be outweighed by an increased possibility of the malignant transformation of the tumour. In spite of benign histopathological features, the course of the disease is unpredictable and warrants close surveillance and serial MRI imaging.

Conflict of interest: The authors declare that they have no conflict of interest.


  1. Aubin MJ, Hardy J, Comtois R. Primary sellar haemorrhagic melanoma: case report and review of the literature. Br J Neurosurg. 1997 Feb;11(1):80-3.
  2. Brat DJ, Giannini C, Scheithauer BW, Burger PC. Primary melanocytic neoplasms of the central nervous systems. Am J Surg Pathol. 1999 Jul;23(7):745-54.
  3. Chappell PM, Kelly WM, Ercius M. Primary sellar melanoma simulating hemorrhagic pituitary adenoma: MR and pathologic findings. AJNR Am J Neuroradiol. 1990 Sep-Oct;11(5):1054-6.
  4. Classen J, Hehr T, Paulus W, Plate K, Bamberg M. Suprasellar melanocytoma: a case of primary radiotherapy and review of the literature. J Neurooncol. 2002 May;58(1):39-46.
  5. Copeland DD, Sink JD, Seigler HF. Primary intracranial melanoma presenting as a suprasellar tumor. Neurosurgery. 1980 May;6(5):542-5.
  6. Coulibaly B, Bouvier C, Paula AM, Fernandez C, Dufour H, Figarella-Branger D. [Pituitary melanocytoma mimicking an adenoma]. Ann Pathol. 2011 Feb;31(1):50-2.
  7. Hayward RD. Malignant melanoma and the central nervous system. A guide for classification based on the clinical findings. Journal of Neurology, Neurosurgery, and Psychiatry. 1976;39:526-30.
  8. Jacob S, Pye E, Hbahbih M, Messios N, Rajabally YA. Rapidly progressive bilateral ophthalmoplegia and enlarging sellar mass caused by amelanotic melanoma. J Neuroophthalmol. 2006 Mar;26(1):49-50.
  9. Louis DN, Ohgaki H, Wiestler OD, Cavenee WK, Burger PC, Jouvet A, et al. The 2007 WHO classification of tumours of the central nervous system. Acta Neuropathol. 2007 Aug;114(2):97-109.
  10. Mohammed AA, Rotondo F, Munoz DG, Kovacs K, Bilbao JM, Karamchandani JR, et al. Diagnostic and prognostic biomarkers of a sellar melanocytic tumor mimicking pituitary adenoma: Case report and literature review. Pathol Res Pract. 2015 Sep;211(9):682-7.
  11. Naul LG, Hise JH, Bauserman SC, Todd FD. CT and MR of meningeal melanocytoma. AJNR Am J Neuroradiol. 1991 Mar-Apr;12(2):315-6.
  12. Neilson JM, Moffat AD. Hypopituitarism caused by a melanoma of the pituitary gland. J Clin Pathol. 1963 Mar;16:144-9.
  13. Perrini P, Caniglia M, Pieroni M, Castagna M, Parenti GF. Malignant transformation of intramedullary melanocytoma: case report. Neurosurgery. 2010 Sep;67(3):E867-9; discussion E9.
  14. Rades D, Tatagiba M, Brandis A, Dubben HH, Karstens JH. [The value of radiotherapy in treatment of meningeal melanocytoma]. Strahlenther Onkol. 2002 Jun;178(6):336-42.
  15. Roser F, Nakamura M, Brandis A, Hans V, Vorkapic P, Samii M. Transition from meningeal melanocytoma to primary cerebral melanoma. Case report. J Neurosurg. 2004 Sep;101(3):528-31.
  16. Rousseau A, Bernier M, Kujas M, Varlet P. Primary intracranial melanocytic tumor simulating pituitary macroadenoma: case report and review of the literature. Neurosurgery. 2005 Aug;57(2):E369; discussion E.
  17. Sakata K, Miyoshi J, Takeshige N, Komaki S, Miyagi N, Nakashima S, et al. Primary meningeal melanocytoma of the sellar region: review of the literature and differential diagnosis with special reference to angiographical features. Pituitary. 2015 Oct;18(5):685-94.
  18. Scholtz CL, Siu K. Melanoma of the pituitary. Case report. J Neurosurg. 1976 Jul;45(1):101-3.
  19. Sidiropoulos M, Syro LV, Rotondo F, Scheithauer BW, Penagos LC, Uribe H, et al. Melanoma of the sellar region mimicking pituitary adenoma. Neuropathology. 2013 Apr;33(2):175-8.
  20. Smith AB, Rushing EJ, Smirniotopoulos JG. Pigmented lesions of the central nervous system: radiologic-pathologic correlation. Radiographics. 2009 Sep-Oct;29(5):1503-24.
  21. Tewari MK, Radotra BD, Sharma BS, Mathuriya SN, Pathak A, Banerjee AK, et al. Meningeal melanocytoma: report of two cases. Indian J Cancer. 1990 Sep;27(3):133-7.
  22. Tuttenberg J, Fink W, Back W, Wenz F, Schadendorf D, Thome C. A rare primary sellar melanoma. Case report. J Neurosurg. 2004 May;100(5):931-4.
  23. Uozumi Y, Kawano T, Kawaguchi T, Kaneko Y, Ooasa T, Ogasawara S, et al. Malignant transformation of meningeal melanocytoma: a case report. Brain Tumor Pathol. 2003;20(1):21-5.
  24. Vezzosi D, Capuani C, Loubes-Lacroix F, Lagarrigue J, Bennet A, Delisle MB, et al. Primary sellar melanocytic tumor: report of new case and literature review. Pituitary. 2009;12(1):51-6.
  25. Wang F, Li X, Chen L, Pu X. Malignant transformation of spinal meningeal melanocytoma. Case report and review of the literature. J Neurosurg Spine. 2007 May;6(5):451-4.
  26. Wang F, Qiao G, Lou X, Song X, Chen W. Malignant transformation of intracranial meningeal melanocytoma. Case report and review of the literature. Neuropathology. 2011 Aug;31(4):414-20.
  27. Zhou HJ, Zhan RY, Ma YH, Cao F, Zheng XJ. Primary sellar melanocytic tumor mimicking hemorrhagic pituitary macroadenoma: Case report and literature review. Br J Neurosurg. 2015 Apr;29(2):298-302.

Contributed by Zielinski Grzegorz, Podgorski Andrzej, Maksymowicz Maria, Witek Przemyslaw, Koziarski Andrzej

Case IndexCME Case StudiesFeedbackHome