Melanotic oncocytic metaplasia of the nasopharynx as a benign mimicker of malignant melanoma: a case report
© Kondo et al; licensee BioMed Central Ltd. 2010
Received: 24 October 2009
Accepted: 14 January 2010
Published: 14 January 2010
Melanotic variant of oncocytic metaplasia of the nasopharynx is an extremely rare condition.
A 73-year-old Japanese man presented with nasal congestion and chill. Nasoscopic examination revealed multiple black nodules around the bilateral torus tubarius. The nodules were biopsied to determine the histology. The clinical differential diagnosis was malignant melanoma or hemangioma. Microscopically, there were oncocytic plump cells with abundant brown pigmented granules showing glandular pattern. No significant atypia was found. The pigment was positive for Fontana-Masson staining, and negative for Berlin blue staining, showing that it was melanin pigment. Immunohistochemically, S100-positive HMB45-negative dendritic cells were also found.
Such a pigmented variant of benign oncocytic lesion is very rare, and only 15 cases have been reported in the English literature. As a benign mimicker of malignant melanoma, melanocytic oncocytic metaplasia should be always taken into consideration in the clinical setting.
In 1995, Shek et al. originally reported two cases of melanotic oncocytic metaplasia of the nasopharynx . Since then, only 13 cases have been reported in English literature [2–5]. We present here an additional case (the 16th case in English literature) of melanotic oncocytic metaplasia in the nasopharynx.
Oncocytic cells are large epithelial cells with eosinophilic, granular cytoplasm. Oncocytic metaplasia (change) is most frequently encountered in certain epithelial organs, such as the salivary gland, the lacrimal gland, the parathyroid gland, the thyroid gland, the pulmonary tree, and the kidney . Oncocytes are not found in these organs of younger persons. The frequency of this oncocytic metaplastic change increases with age, its exact significance and biological function are, however, still unknown . It is generally believed that the oncocyte represents a form of cellular degeneration . Because oncocytes are discovered predominantly in elderly persons, they have undergone cytoplasmic change and are considered to be involved in an aging process .
Oncocytic change in the upper respiratory tract is an uncommon finding and melanotic variant of oncocytic metaplasia of the nasopharynx is an extremely rare condition. To our knowledge, 15 cases have been reported in the literature and our case is the 16th case.
The lesion may be single or multiple. Most of the lesions are asymptomatic and tend to be incidentally discovered during examination of the nasopharynx. Some of these lesions may occasionally produce symptoms. When the mucosa around the opening of Eustachian tube is affected, ear or nose symptoms may occur. Eustachian tube dysfunction can be caused when the tissue edema accompanying the lesions impairs the tube function. In this case, the feeling of nasal congestion (obstruction) may be due to Eustachian tube dysfunction, and the chill may be coincidental.
All reported cases including our case are elderly males in their sixties or seventies. The lesion may be misinterpreted clinically as early nasopharyngeal carcinoma, nevus, or malignant melanoma. The origin of the melanin pigment is in question. The exact nature of melanin-containing oncocytes in the nasopharynx awaits further clarification.
In conclusion, we report the 16th case of melanin-containing oncocytic metaplasia of the nasopharynx. As a benign mimicker of malignant melanoma, melanocytic oncocytic metaplasia should be always taken into consideration in the clinical setting.
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
We thank Miki Zenigami-Yamazaki, Noriko Sakamoto, and Shuichi Matsuda at Kobe University for their excellent technical assistance.
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