Poorly Differentiated Chordomas Showing Loss of INI1/SMARCB1: A Report of 2 Rare Cases With Diagnostic Implications

Abstract

Poorly differentiated chordomas are rare musculoskeletal tumors. Case 1. A 42-year-old lady presented with quadriparesis of 2 months' duration. Radiologic imaging disclosed a soft tissue mass in her left prevertebral- and paravertebral cervical region. Case 2. A 4-year-old male child presented with neck pain and restricted head movements of 1-year duration. Radiologic imaging revealed a contrast enhancing, paraspinal soft tissue mass in his cervical region. Microscopic examination in both the cases revealed a cellular malignant tumor composed of moderate to markedly pleomorphic cells with interspersed mitotic figures, along with focal myxoid change and necrosis. By immunohistochemistry, tumor cells in both cases were diffusely positive for pan cytokeratin (AE1/AE3) and brachyury, whereas these were negative for INI1/SMARCB1. Tumor cells in the second case were also positive for glypican3. The first case developed pulmonary metastasis, while the second case developed recurrence. Poorly differentiated chordomas are uncommon tumors, invariably characterized by loss of INI1. These tumors can be rarely seen in adults and need to be differentiated from their diagnostic mimics, in view of treatment implications and their relatively aggressive clinical outcomes.

Poorly differentiated chordoma: review of 53 cases

“…Some cases were reported to show active to chronic inflammatory infiltrate ( Fig. 1D and 1) (2,5,10). All cases demonstrated mild to moderate pleomorphism.…”

“…Neoplastic cells are typically negative for GFAP, desmin, and actin. Differential keratin expression of PDC is not well studied and needs to be more precisely addressed: keratins 7 and 20, which are known to be expressed in classical chordoma, were both negative in only two studied cases (2,15). Few cases have been shown to express neurofilament and galectin-3.…”

“…Chordomas are classically characterized by cords and trabeculae of physaliphorous cells in a chondromyxoid background. Among variable morphological features, they share similar immunophenotype, showing positivity for pan‐cytokeratin, S100, EMA (epithelial membrane antigen), and brachyury, the latter being the most sensitive and specific, and mainly used in the diagnosis of the extra‐axial suspected lesions . Apart from these three types of chordoma, Hoch et al have described a new variant – called poorly differentiated chordoma (PDC) – in detail with its distinct morphological features particularly in the pediatric population with generally worse outcome .…”

“…Inclusion criteria in this review included involvement of axial skeleton (vertebra and clivus, which are common locations for classical chordoma), INI1 loss (either with the aid of immunohistochemistry or various molecular techniques), and immunohistochemical brachyury expression. According to these qualifications, we came up with 53 cases reported up to March 2018, from different institutions (2)(3)(4)(5)(8)(9)(10)(11)(12)(13)(14)(15). The clinical, imaging, histopathological features, and immunohistochemical and molecular findings of those 53 cases were given in Table 1 and summarized in Table 2.…”

Soft Tissue Special Issue: Chondroid Neoplasms of the Skull

“…Decalcification of the tissue may also lead to loss of brachyury expression. Studies have reported loss of INI-1 staining in poorly differentiated chordoma, particularly in children [73][74][75][76][77][78][79][80][81].…”