Plexiform schwannoma

Symplastic/pseudoanaplastic giant cell tumor of the bone

OBJECTIVE

Giant cell tumor of bone (GCTB) is a locally aggressive primary bone tumor. Its malignant counterpart is quite rare. Rarely, a conventional GCTB shows marked nuclear atypia, referred to as symplastic/pseudoanaplastic change, which can mimic sarcomatous transformation. Recently, somatic driver mutations of histone H3.3 exclusively in H3F3A have been described in GCTB. We report a series of 9 cases of GCTB with symplastic/pseudoanaplastic change, along with analysis of H3F3A variants.

MATERIALS AND METHODS

Nine cases of GCTB with symplastic change were identified. Clinico-radiological features, morphological features, and immunohistochemical stain for Ki-67 stain were reviewed. H3F3A variants were also analyzed using Sanger sequencing.

RESULTS

Histologically, conventional giant cell tumor areas with scattered foci of markedly atypical cells were seen in all of the cases and all showed rare if any Ki-67 labeling. One patient had received denosumab treatment and another radiation therapy. Radiological features were characteristic of conventional GCTB. Mutation in H3F3A (p.Gly34Trp [G34W]) was found in 6 of the 7 cases. Clinical follow-up ranged from 6 to 208 months. Local recurrences were seen in 4 cases (44 %).

CONCLUSIONS

GCTB with symplastic/pseudoanaplastic change is an uncommon variant of conventional GCTB, which can mimic primary sarcoma or sarcomatous transformation. These tumors possess the same missense mutation in histone H3.3 as conventional GCTB.

Intraosseus plexiform schwannoma of the mandible: immunohistochemical differential diagnosis

Schwannomas and neurofibromas are the most common benign tumors derived from peripheral nerves, and whereas the head and neck region is the most common location for the occurrence of benign neural sheath neoplasms, origin within the oral cavity is uncommon, and occurrence centrally in the jaws is most unusual. Plexiform (multinodular) schwannoma is an anatomically unique variant of schwannoma characterized grossly and/or microscopically by intraneural plexiform and often multinodular growth. In current report, we present the first reported case of intraosseous plexiform schwannoma of the mandible, an extremely rare benign neurogenic tumor, diagnosed by optical and immunohistochemical procedures, showing the importance of differential diagnosis of these unusual intraosseous mandibular tumors.

Plexiform schwannoma of the foot: a review of the literature and case report

Plexiform schwannoma is a rare variety of benign nerve sheath tumor that is usually confined to the head and neck or trunk. In this article, we describe the case of a plexiform schwannoma of the foot in an adult male. In addition to a review of the literature, we discuss diagnostic characteristics and differentiators for this tumor, an approach to surgical treatment, including reconstruction of the plantar foot defect after tumor extirpation, and why it is important for practicing foot and ankle surgeons to differentiate plexiform schwannoma from other similar tumors.

Cutaneous myoepithelioma with a plexiform pattern of growth: a case report

Cutaneous myoepithelioma, a recently recognized, rare but well-characterized entity, is comprised solely of myoepithelial cells. In this report, we describe a cutaneous myoepithelioma with a plexiform pattern of growth in the scapular region of a 58-year-old woman.

Contiguous conventional and plexiform schwannomas

✓The authors present clinical, imaging, and histological features of two adult patients found to harbor a conventional schwannoma contiguous with a deep plexiform schwannoma. One patient had neurofibromatosis (NF) Type 2 (NF2), and both intracranial (bilateral oculomotor, trigeminal, acoustic, and hypoglossal schwannomas as well as meningiomas) and intraspinal (schwannomas and meningiomas) lesions. The proximal forearm lesions consisted of a conventional schwannoma and an underlying plexiform component. The second patient, who did not have NF2, presented with a similar enlarging mass in the distal arm; two contiguous lesions were resected. Both patients exhibited distinct, readily identifiable, magnetic resonance imaging features. Plexiform schwannomas are rare lesions that occur sporadically or, on occasion, in association with NF2 or meningiomas with or without multiple schwannomas. The authors believe that a more careful examination of patients with NF2 may show that these people have a higher incidence of plexiform schwannoma than previously thought. Pathological confirmation is crucial in distinguishing plexiform schwannomas from plexiform neurofibromas, because the latter are directly associated with NF1 and have a significant tendency to undergo malignant transformation. To the best of the authors’ knowledge, this is the first report of a conventional schwannoma contiguous with a deep plexiform schwannoma.