Benign Glandular Schwannoma With Ancient Change

Glandular Schwannoma With Apocrine Decapitation Secretion: A True Divergent Differentiation or Entrapped Normal Tissue?

ABSTRACT

We report an unusual case of schwannoma with glandular elements that demonstrated apocrine decapitation secretion. The glandular structures were embedded within the tumor, varied in shape and size, and were lined by a double-to-multilayered epithelium, with the inner layer composed of monomorphous cuboidal to columnar cells, focally with apocrine decapitation secretion, and the outer layer representing myoepithelial cells. A normal eccrine unit was observed near the lesion. Immunohistochemical studies showed that all luminal cells of the glandular structures stained positive for CK7, whereas myoepithelial cells expressed S100 and p63, and epithelial membrane antigen highlighted the luminal border. CK20 and neuroendocrine markers were negative in the glandular elements.Our findings suggest that the origin of the glandular elements in our case was represented by entrapped glands. Two theories may explain the epithelial hyperplasia observed in the present case as follows: the obstructive effect theory and the inductive ability of a mesenchymal proliferation to produce epidermal or adnexal changes. We suggest that, in a subset of cases, the origin of the glandular elements might represent entrapped glands, wherein their histomorphology/cytomorphology recapitulates the elements comprising the normal adjacent tissue. Further research is necessary to elucidate the histogenesis of glandular schwannoma.

Benign Neurofibroma/Schwannoma Hybrid Peripheral Nerve Sheath Tumor of the Ulnar Nerve Harboring a Metastatic Papillary Thyroid Carcinoma Deposit: A Case Report of Tumor-to-Tumor Metastasis

A 74-year-old man with a medical history significant for papillary thyroid cancer (PTC) presented with a rapidly enlarging grape-sized mass in his right medial arm with paresthesia in the ulnar nerve distribution. Imaging was suspicious for a peripheral nerve sheath tumor (PNST), but an ultrasound-guided biopsy was equivocal. The mass was excised with final histopathology demonstrating a benign neurofibroma/schwannoma hybrid nerve sheath tumor (N/S HNST) harboring a metastatic PTC deposit, ultimately mimicking the rare glandular schwannoma subtype. Next-generation sequencing (NGS) of the lesion demonstrated somatic variants in BRAF and TERT (common in PTC) and NF2 (common in PNSTs). After excision, the patient's nerve symptoms improved. A postsurgical PET/CT scan also showed progression in the lungs/mediastinum. Due to the metastatic nature of his PTC, he was treated with 14 mg of Lenvima (lenvatinib) daily, and his PET/CT surveillance was performed at more frequent intervals. Tumor-to-tumor metastasis (TTM) is a rare occurrence. To our knowledge, this is the first case reported on PTC metastasizing into a benign (hybrid) PNST, which mimicked glandular schwannoma. Symptomatology, imaging characteristics, NGS, and histopathological characteristics that can decipher between different benign PNST subtypes (schwannoma, neurofibroma, glandular, hybrid, etc.), malignant PNSTs (MPNSTs), and TTM are described.

What's new in nerve sheath tumors

Peripheral nerve sheath tumors are commonly encountered and frequently pose challenges to the pathologist and the clinician. This review discusses the wide range of entities with an emphasis on new discoveries in the past decade. Clinical, histologic, immunohistochemical, and pathogenetic findings are discussed with an emphasis on clinical implications and differential diagnosis.

Glandular Schwannoma: An Uncommon Variant of Schwannoma with Controversial Histogenesis

Schwannomas are benign, encapsulated nerve sheath tumors arising from Schwann cells; several histologic variants of schwannoma have been described, including the exceedingly rare glandular schwannoma (GS). The histogenesis of the glands in GS (as well as in other peripheral nerve sheath tumors with a glandular component) remains unclear; no consensus exists as to whether glands should be interpreted as metaplastic elements or entrapped reactive glands. We report a case of GS with detailed immunohistochemical analysis of the epithelial component. We believe that our findings raise further questions regarding the histogenesis of glands in GS, casting doubts on the traditional distinction between true metaplasia and glandular entrapment. Further research is warranted in this regard.

Schwannoma-Like Pleomorphic Adenoma: Two Cases and a Review of the Literature

Schwannoma-like pleomorphic adenoma is a rare variant of the common benign salivary neoplasm, pleomorphic adenoma. This entity's cytomorphology closely mimics a schwannoma, potentially making a diagnosis of cytologic preparations or of surgical specimens a challenge. To the best of our knowledge, there are only six previous reports of schwannoma-like pleomorphic adenoma with eight total cases in the English language literature prior to the addition of the two cases detailed in this report. Our report includes what we believe to be the first documented case of this entity occurring in the submandibular gland. One of our cases occurred in the submandibular gland of a 90-year-old woman and the other occurred in the left parotid gland of a 40-year-old woman. We also examine the diagnostic considerations used to differentiate these two entities.

Divergent Schwannoma-Like Phenotype in a Pleomorphic Adenoma

The schwannoma-like pleomorphic adenoma is a rare histopathological variant of the pleomorphic adenoma. Five previous reports with seven cases exist in English language literature. These tumors present in the parotid gland most commonly. Intraparotid schwannomas of the facial nerve and schwannomas with glandular differentiation have also been reported. A 60-year-old male presented with an asymptomatic swelling over the left angle of the mandible. The swelling had been present for about 12 years with a recent increase in size. CT imaging showed a hyperdense circumscribed mass of the superficial lobe of the parotid. The working diagnosis was that of a benign tumor of salivary gland or soft tissue origin. The mass was excised with careful preservation of the facial nerve. The 3.5 cm mass was submitted for histopathological examination. The well-circumscribed, encapsulated mass showed a predominant sheet-like proliferation of Antoni type A-like tissue, Foci of glandular differentiation with duct-like structures were also seen. Cytological atypia or mitotic activity were not seen. Nuclei of lesional cells diffusely and strongly expressed reactivity to p63. The final diagnosis was a schwannoma-like pleomorphic adenoma. No recurrence has been reported in the 15 months since the removal. Facial nerve function is unimpaired with a House Brackmann facial nerve function score of one. The potential for misdiagnosis in fine needle aspirate and incisional biopsies is real in cases of schwannoma-like pleomorphic adenoma. The diagnostic pitfalls include the schwannoma and leiomyoma. Schwannomas with glandular differentiation have also been reported and therefore a misdiagnosis may potentially occur in excised specimens. Careful application of immunohistochemistry may help in the differentiation of these lesions.