Adamantinoma-Like Ewing Sarcoma of the Parotid Gland: Report of Two Cases and Review of Literature

Adamantinoma-Like Ewing Sarcoma of the Head and Neck: A Case-Series of a Rare and Challenging Diagnosis

Adamantinoma-like Ewing sarcoma (ALES) is a rare malignant tumor characterized by EWSR1::FLI1 related fusions and complex epithelial differentiation. ALES poses a tremendous diagnostic challenge owing to its resemblance to a wide variety of common head and neck malignancies. We aimed to study the clinicopathologic spectrum of ALES diagnosed at our institute. A retrospective review of the clinical and pathologic features of all EWSR1-rearranged ALES cases was performed after confirming the diagnosis. The cases lacking EWSR1 rearrangement were excluded. A total of 7 patients were analyzed. The median age was 27 years (range 7-42 years). There were 4 males and 3 female patients. Tumors were distributed as follows: maxilla (n = 2), parotid (n = 2), nasal cavity (n = 1), ethmoid/maxilla (n = 1), and thyroid (n = 1). Tumor size ranged from 2.2 to 5.5 cm. On microscopy, tumors displayed nested-lobular architecture, monomorphic cells, and interlobular fibrotic stroma. Other features included: palisading (n = 5), squamous differentiation (n = 2), keratinization (n = 1), colonisation of salivary ducts (n = 1) and thyroid follicles (n = 1), follicle-like cysts (n = 3), calcification (n = 2), necrosis (n = 3). Mitotic rate was 4-15/2 mm². On immunohistochemistry, cytokeratins (100%), p40 (100%), strong/diffuse membranous CD99 (100%), NKX2.2 (100%), Fli-1 (71%), and synaptophysin (71%) was positive. Patients received chemotherapy (n = 7) and radiotherapy (n = 4). Two patients developed recurrence at 6 and 10 months; 3 developed metastases at 0, 6, and 25 months. ALES is a rare and aggressive malignancy that mimics diverse neoplasms common in the head and neck region. Awareness of the morphologic and immunohistochemistry spectrum of this tumor is essential to avoid diagnostic errors.

Basaloid squamous cell carcinoma with prominent shadow (ghost) cell differentiation. An unreported neoplasm of the parotid gland

Basaloid squamous cell carcinoma (BSCC) is an aggressive type of squamous cell carcinoma (SCC) predominant in the upper aerodigestive tract. To our knowledge, only one case of that tumor has been previously described in the parotid gland. Shadow (ghost) cell differentiation (SCD) is a specialized form of keratinization characteristic of pilomatricoma, and other skin tumors with follicular differentiation. SCD has also been described infrequently in some visceral carcinomas and rarely in the minor salivary glands. Recently, an SCC with prominent SCD has been reported in the parotid. We report for the first time the case of parotid BSCC with prominent SCD in an 87-year-old man. He was admitted due to the appearance in the last few months of a mass, painful on palpation, in the left parotid region. Imaging studies and tru-cut biopsies indicated the need for surgical removal. A left superficial parotidectomy, including the branch of the cervicofacial nerve, was performed. The BSCC showed predominance (62%) of SCD. Immunohistochemically, the basaloid cells were positive for β-catenin, pan-cytokeratin (pan-CK) AE1∕AE3, CK19, high-molecular-weight CK (HMWCK), p63, p40, and cluster of differentiation 10 (CD10) in a diffuse pattern. No signs of recurrence or metastasis were observed four months after surgery. The main differential diagnoses include nuclear protein in testis (NUT) carcinoma, adamantinoma-like Ewing sarcoma, embryonal carcinoma, and basal cell adenocarcinoma of the solid type. SCD in BSCC of the parotid should be recognized to avoid misdiagnosis, especially in small samples. Although rare, BSCC with SCD should be added to the list of tumors that may originate in the parotid gland.

Adamantinoma-like Ewing Sarcoma of the Nasal Cavity: A Rare Clinical Presentation with Deceptive Histopathologic Features

Ewing sarcoma (ES) is a malignant round cell tumour (MRCT) that usually involves bone and soft tissue of young and paediatric populations. ES of the head and neck region is uncommon. Adamantinoma-like Ewing sarcoma (ALES) is a rare variant of ES that shows complex epithelial differentiation on histopathology and immunohistochemistry (IHC). It demonstrates a t(11;22) translocation and EWSR1- FLI1 fusion. Most documented cases of ALES of the head and neck region were initially misdiagnosed as epithelial tumours. We present a rare case of ALES of the nasal cavity in a young female. The patient subsequently underwent chemotherapy and showed an excellent response. Awareness of this entity is important for pathologists and oncologists due to its distinct therapeutic and prognostic implications. We propose performing upfront NKX2.2 and CD99 IHC studies, as well as other lineage specific IHC markers, in any poorly differentiated MRCT of head and neck region.