Nasal pleomorphic adenoma with skeletal muscle differentiation: potential misdiagnosis as rhabdomyosarcoma

An unusual localization of a pleomorphic adenoma in the rhinopharynx

Pleomorphic adenoma is the most common benign tumor of the parotid glands. Rarely it may arise from minor salivary glands of the upper aerodigestive tract. A 57-year-old woman was admitted at our institution presenting with nasal obstruction. Endoscopic evaluation revealed a pedicled mass in the rhinopharynx. After radiological examination, we opted for a transnasal endoscopic-assisted excision of the mass under general anaesthesia. Histological evaluation deponed for pleomorphic adenoma with clear surgical margins. No endoscopic evidence of local recurrence has been shown after 48 months of followup. In the literature, few cases of pleomorphic adenoma arising in the rhinopharynx have been reported. The introduction of endoscopy, as shown by our experience, leads to important benefits in the identification, treatment, and followup of such rhinopharyngeal benign tumors.

Pleomorphic adenoma of minor salivary gland with therapeutic misadventure: a rare case report

Background

The benign tumors of nasopharynx are least encountered tumors in otolaryngology, as nasopharynx is considered one of notorious anatomical site for the malignant tumors. Pleomorphic adenoma of the minor salivary gland of nasopharynx and parapharyngeal space is rare. We present a pleomorphic adenoma of minor salivary gland which was mismanaged.

Case presentation

An adult male presented with left nostril obstruction for five months. The examination found big mass extending from nasopharynx to oropharynx. On CT scan, this tumor was quite big and extending to the parapharyngeal space. The FNAB found it a carcinoma but it did not respond to radiotherapy. The excision biopsy of tumor revealed it as pleomorphic adenoma. We found only five published reports on this tumor arising from nasopharynx.

Discussion and conclusion

Although, in this case report exact origin of the tumor could not be ascertained as it also appeared to be a parapharyngeal tumor but we kept the possibility of a nasopharyngeal tumor on the basis of clinical features. The pleomorphic adenoma of nasopharynx is rare. It can be misdiagnosed as malignant epithelial tumor on histopathology. The differentiation from its malignant variant is also difficult. A possibility of benign tumor should always be kept in nasopharyngeal growth with no evidence of metastasis, and histopathological diagnosis of growth should be available before any definitive treatment.

Nasopharyngeal pleomorphic adenoma in the adult

INTRODUCTION

Salivary gland tumors account for less than 5% of all neoplasms in the head and neck, with pleomorphic adenoma being the most common type. These typically arise in the palate, but we report a rare case of nasopharyngeal pleomorphic adenoma in an adult.

MATERIALS AND METHODS

The authors conducted a case report and literature review.

RESULTS

The patient presented with unilateral otalgia, tinnitus, and aural fullness. Nasal endoscopy revealed a pedunculated mass adjacent to the left torus tubarius and he was treated with an excisional biopsy. Histologic evaluation demonstrated pleomorphic adenoma.

DISCUSSION

Pleomorphic adenomas seldom present as nasopharyngeal masses and have a nonspecific appearance on endoscopy. Microscopic examination has characteristic features to aid in an accurate diagnosis. Treatment is surgical and recurrence is unlikely.

The ultrastructural aspects of neoplastic myoepithelial cell in pleomorphic adenomas of salivary glands

The purpose of this study has been to establish the major ultrastructural aspects of the myoepithelial cell and the myoepithelial-like cells proliferated in the pleomorphic adenomas of salivary glands. Thus, twelve benign pleomorphic adenomas of salivary glands have been studied by electron-microscopy transmission techniques. Our analysis has proved the proliferation of two major cellular populations, one of ductal type and one of myoepithelial type, which tried to reproduce the tubulo-acinar cytoarchitecture from the normal salivary glands. We have also noticed the key role of the so-called 'modified' myoepithelial cells from the periphery of the proliferating epithelial units in the genesis of the myxoid and chondromyxoid tumoral stromal areas. All these ultrastructural aspects have explained the great histological diversity of these salivary gland neoplasms as well as the key role of the myoepithelial cell in its histogenesis.

Malignant rhabdoid tumor arising from a pleomorphic adenoma

Malignant transformation of pleomorphic adenomas often occurs in long-standing tumors or tumors with multiple local recurrences. The malignant component is usually a carcinoma. The case reported herein concerns a 60-year-old man who had a malignant rhabdoid tumor arising in a painless parotid mass that remained untreated for 25 years. Malignant rhabdoid tumors are clinically aggressive neoplasms with phenotypic features that resemble rhabdomyomatous differentiation but lack genuine skeletal muscle differentiation. The salient features of rhabdoid tumor cell include large, pleomorphic, and eccentric nucleus and a solitary and prominent intracytoplasmic inclusion that is strongly immunoreactive for vimentin. It is our understanding that this is the first reported case of malignant rhabdoid tumor arising in the parotid gland in the English literature. The pathologic features of our case will be discussed in context with malignant rhabdoid tumors from other parts of the body.

Small cell neuroendocrine carcinoma with skeletal muscle differentiation: report of three cases

Three cases of neuroendocrine carcinoma showing skeletal muscle differentiation are presented. The tumors were located in the skin and subcutaneous tissue, the urinary bladder, and the nasal cavity respectively, and were composed by two cell types admixed intimately with each other. One cell type had features identical to those seen in conventional small cell neuroendocrine carcinoma, including scanty cytoplasm, round nuclei with fine granular chromatin, immunohistochemical reactivity for neuron-specific enolase, chromogranin and cytokeratins, and electron-dense granules on ultrastructural examination. The second cell type was either plasmacytoid or elongated and straplike, with abundant eosinophilic cytoplasm and irregular nuclei with prominent nucleoli. These cells showed immunohistochemical positivity for desmin, sarcomeric actin, myoglobin, and myogenin. They also exhibited ultrastructural evidence of rhabdomyoblastic differentiation in the form of contractile filaments with abortive Z-band formation. An origin from a cell capable of dual differentiation toward neuroendocrine and rhabdomyoblastic elements is postulated for these tumors.