A 82‐Year‐Old Man with an Extra‐Axial Frontal Mass

Clinical History

A 82‐year‐old male presented with a 3‐month lasting progressive cognitive deterioration, particularly regarding temporospatial orientation and short‐term memory. Previous medical history included colorectal carcinoma with liver metastases, prostatic carcinoma, type 2 DM and arterial hypertension. No focal neurological signs were elicited, and a MRI scan (Figure 1A) showed an extra‐axial fronto‐basal tumor, with heterogenous contrast enhancement and dural tail sign (not seen in the image). A large cyst between the lesion and the cortex could also be seen. A frontal craniotomy with total excision of a non‐infiltrative, dural‐adherent mass was performed.

Figure 1.

Microscopic Examination

H&E sections disclosed a high cellular and vascularized tumor where pigmented cells could easily be seen (Figure 1B). These cells were localized, as much near the vessels as far from them, in the core of the tumor parenchyma, and indistinguishable from neoplastic elements (Figure 1C). Neoplastic cells were mainly spindled or oval with sheeting arrangements and intermingle with pigmented cells (Figure 1D). Focally, nests of neoplastic cell with intervening stroma containing also pigmented cells could be seen (Figure 1E). No nuclear pseudo‐inclusions, pseudo‐syncytial areas, whorls or psammoma bodies were elicited. Pigment became evident with Perls' staining (Figure 1F) but not with Fontana‐Masson. Neoplastic cells displayed extensive reactivity for EMA (Figure 1G), vimentin (Figure 1H) and progesterone receptor (Figure 1I), but negativity for S100, Melan A (Figure 1J) and HMB‐45. There were no anaplastic features, including high mitotic or proliferative (Ki67) indexes. What is your diagnosis?

Diagnosis

Meningioma with iron‐positive macrophages.

Discussion

Macrophage reaction with iron deposits is a common reaction to all vascularized nervous system pathologies, including tumors. Most of the times, the nature of these deposits is easily diagnosed by performing an iron stain. However, in selected cases, and basically at histomorphology grounds, the early differentiation from melanin deposits may be difficult, either, among a few causes, because the pigment may be found far from the vessels or because the tumor appearance respects one of those with melanin deposits. Indeed, deposition of melanin may occur in circumscribed tumors of the nervous system, the so‐called pigmented tumors. These well‐known entities may encompass metastatic melanoma, the most frequent by far, pigmented schwannomas, melanotic medulloblastomas, pigmented glial/ependymal and choroid plexus tumors, melanotic neuroectodermal tumors of infancy, and teratomas 1. However, if one considers the meninges pigmented‐related neoplasms, the primary melanoma and the meningeal melanocytoma must be added. These tumors are thought to arise from leptomeningeal melanocytes neural crest derive 1, and they should display reaction with the anti‐melanosomal antibodies HMB/45 and Melan A, and S100(4).

The histomorphology of this tumor very much suggests a meningeal melanocytoma, that is, fusiform‐shaped arranged in sheets and in nests cells and without anaplasia. Melanocytomas are extremely rare and they may occur anywhere in the cranial and spinal meninges, approximately two‐thirds arising in the intracranial compartment 5. Furthermore, no typical histomorphological features suggesting a meningioma was elicited in the studied samples whatsoever. However, immunohistochemistry data strongly favor this diagnostic. Indeed, the vast majority of meningiomas stain for EMA and vimentin, and progesterone receptor reactivity may also be of help 4. Besides, MRI data also suggested a meningioma 2.

Colonization of nonpigmented tumors by pigmented melanocytes has been reported in extracranial neoplasms tumors occurring in several places of the body. Specifically, one case of melanocytic colonization of a meningioma confirmed by immunohistochemistry, ultrastructural analysis and molecular genetic has been described 3. This tumor should be considered a meningioma with iron‐positive macrophages on immunohistochemistry and conventional histomorphology staining grounds, respectively, and also stresses the still value of ancient stains for the diagnosis of particular aspects of nervous system tumors.