When a dermatopathologist encounters the ultra-rare: A case series of superficial soft tissue/cutaneous myxopapillary ependymomas

Abstract

Myxopapillary ependymoma (MPE) is an uncommon variant of ependymoma, almost exclusively seen in conus medullaris or filum terminale. MPE can be diagnostically challenging, especially when arising extra-axially. Here we report 5 cases of superficial soft tissue/cutaneous MPE, identified across three tertiary institutions. All patients were female and three of them (3/5, 60%) were children (median age 11 years, range 6-58 years). The tumors presented as slow-growing masses of the sacrococcygeal subcutaneous soft tissues, occasionally identified after minor trauma and clinically favored to be pilonidal sinuses. Imaging showed no neuraxis connection. Macroscopically, tumors were well-circumscribed, lobulated, and solid and microscopically they exhibited typical histopathology of MPE, at least focally. Two of the tumors (2/5, 40%) showed predominantly solid or trabecular architecture with greater cellular pleomorphism, scattered giant cells, and increased mitotic activity. All tumors (5/5, 100%) showed strong diffuse immunohistochemical expression of GFAP. One tumor clustered at the category "ependymoma, myxopapillary" by methylome analysis. Two patients (2/5, 40%) had local recurrence at 8 and 30 months after the initial surgery. No patients developed metastases during the follow-up period (median 60 months, range 6-116 months). Since a subset of extra-axial MPEs behaves more aggressively, timely and accurate diagnosis is of paramount importance.

Keywords: GFAP; cutaneous; methylation; myxopapillary ependymoma; superficial.

Figure 1.

Case 1: 11-year-old girl with 2.3 cm sacrococcygeal subcutaneous MPE. (A) Low-power view depicting localization of the tumor in the subcutaneous fibroadipose tissue (H&E 10x). (B) The tumor shows areas of solid architecture with evident cellular pleomorphism (H&E x100) including (C) bizarre giant cellular forms (H&E x200). (D) Diffuse and strong expression of GFAP (x100).

Figure 2.

Case 2: 6-year-old girl with 2.8 cm precoccygeal soft tissue MPE. (A) Low-power view (H&E x10) showing the relationship of the tumor with the overlying epidermis (H&E 10x). (B) The tumor exhibits mostly tubulopapillary architecture (H&E x100) but also (C) areas with nested architecture and increased mitotic activity. Frequent intranuclear inclusions are also noted (H&E x200). (D) Strong and diffuse GFAP expression (x100).

Figure 3.

Case 3: 58-year-old woman with MPE of the lower back, overlying the coccyx. (A) Low-power view highlighting localization of the tumor in the subcutaneous fibroadipose tissue (H&E x10). (B) The tumor shows classic papillary and tubulocystic architecture with perivascular pseudorosettes (H&E x100) and (C) areas of increased mitotic activity (H&E x200). (D) Diffuse and strong expression of GFAP (x100).

Figure 4.

Case 4: 33-year-old woman with MPE paramedially, left caudal to coccyx. (A) Low-power view showing tumor soft tissue localization (H&E x10). (B) The tumor shows classic MPE morphology with typical tubulopapillary architecture (H&E x100) and (C-D) abundant perivascular pseudorosettes (C: H&E x100; D: H&E x200).

Figure 5.

Case 5: 8-year-old girl with natal cleft MPE. (A-B) The tumor shows tubulocystic architecture (A: H&E x10; B: H&E x100), with (C) mostly clear cell morphology and perivascular pseudorosettes (H&E x200). (D) Strong and diffuse positivity for GFAP (x100).

Figure 6.

DNA methylation profiling of myxopapillary ependymoma. (Top) Uniform Manifold Approximation and Projection (UMAP) dimensionality reduction plot of Central Nervous System tumors showing that the current case (Case 1, indicated by arrow) clusters with other known myxopapillary ependymomas based on its genome-wide DNA methylation signature. (Bottom) Copy number plot highlighting aneuploidy of this myxopapillary ependymoma, including loss of chromosomes 1, 2, 8, 10, 13, and 22 with gains of chromosomes 3, 9, 11, 15, 17, 18, 19, 20, and 21.