Trichoblastic carcinosarcoma with panfollicular differentiation (panfollicular carcinosarcoma) and CTNNB1 (beta-catenin) mutation

Abstract

We present a case of trichoblastic carcinosarcoma with panfollicular differentiation. An 80-year-old man presented with a lesion on the left ear, which had been present for several months. Histopathology revealed a well-demarcated neoplasm in the dermis composed of intimately intermingled malignant epithelial and mesenchymal cells. The epithelial component showed multilineage follicular differentiation toward all of the elements of a normal hair follicle. Molecular analysis revealed identical molecular aberrations in both epithelial and mesenchymal components including CTNNB1 and SUFU mutations. To the best of our knowledge, this is the first report of panfollicular carcinosarcoma and of the presence of a CTNNB1 mutation in trichoblastic carcinosarcoma.

FIGURE 1

Scanning magnification demonstrates a biphasic cutaneous tumor (A, H&E magnification 61×), the tumor consisted of an epithelial follicular germinative cell component intimately intermingled with the mesenchymal component (B,C, H&E magnification 200×), epithelial component composed of atypical cells with polymorphic and pleomorphic nuclei (D, H&E magnification 200×), also note the multinucleated pleomorphic cells with prominent nucleoli dispersed between the spindle cells (E; H&E magnification 200×)

FIGURE 2

Figure 2 A‐D, Histopathological features of the various differentiation: inner root sheath differentiation of the bulb and stem with ghost/matrical cells (A, H&E magnification 100×), and bright red trichohyalin granules; (B, H&E magnification 200×). Infundibular differentiation with infundibulocystic and squamous structures surrounded by mesenchymal cells (C, H&E magnification 120×). Cells with signet ring cell appearance (myoepithelial differentiation) (D, H&E magnification 200×). Eosinophilic cells with central apoptosis (trichilemmal differentiation of outer root sheath) (E, H&E magnification 100×)

FIGURE 3

Figure 3 A‐G, Area with epithelial and mesenchymal component (A, H&E magnification 100×), strong nuclear beta‐catenin expression was noted in both epithelial and mesenchymal cells (B, magnification 100×), cytokeratin AE1/AE3 showed strong expression in epithelial cells and negative staining in mesenchymal cells. (C, magnification 50×), p63 were strongly expressed in malignant epithelial cells, while negative in mesenchymal cells (D, magnification 50×), BerEP4 showed focally weak expression in the malignant epithelial cells (E, magnification 50×), Ki‐67 proliferation was high in both components (F, magnification 50×), aberrant expression of p53 was demonstrated in both components (G, magnification 50×)