Pleomorphic adenoma with nuclear palisading arrangement of modified myoepithelial cells: Histopathologic and immunohistochemical study.

Abstract

Pleomorphic adenomas with a nuclear palisading arrangement of spindle-shaped modified myoepithelial cells (MMCs), suggesting the appearance of palisading leiomyoma or Antoni's A type of neurilemmoma, are quite rare, and its cytologic nature has been poorly understood. This paper reports histologic and immunohistochemical findings of palisading MMCs in two cases of pleomorphic adenoma. Histologically, foci of spindle-shaped MMCs with nuclei in a palisading arrangement were scattered in the myxoid areas. Near the large foci of spindle-shaped MMCs with nuclear palisading arrangements, tiny foci of spindle-shaped MMCs forming nuclear palisading or rosettelike arrangements were seen. Such nuclear palisading arrangements of MMCs were suggestive of differentiation or transformation of MMCs into cells that were more smooth muscle in nature, supported by occasional existence of palisading leiomyoma in the myometrium and gastrointestinal tract. However, immunohistochemical findings of palisading MMCs in pleomorphic adenoma were similar to those of non-palisading MMCs, and showed no evidence of smooth muscle differentiation; neither palisading nor non-palisading MMCs in pleomorphic adenoma expressed desmin, muscle specific actin (HHF-35), alpha smooth muscle actin, or myoglobin.The biologic significance and formative mechanism of nuclear palisading arrangement of MMCs in pleomorphic adenoma could not be determined in the present study. However, if the MMCs with nuclear palisading arrangements in pleomorphic adenoma, presented here, are aspirated for cytologic diagnosis or are included in a small biopsy specimen, the correct diagnosis of pleomorphic adenoma may be confused by a suspicion of myogenic or neurogenic tumor.

Schwannoma-Like Pleomorphic Adenoma: A Case Report with Review of the Literature

“…Although PAs tends to be well circumscribed, small extensions can be seen protruding into the adjacent normal tissue in a pseudo-infiltrative pattern. Epithelial cells of pleomorphic adenoma originate from duct epithelial and myoepithelial cells [1,3]. Epithelial tumor cells are cuboidal in shape and line duct-like structures that vary in size and shape.…”

Schwannoma-like pleomorphic adenoma of the parotid

“…16–18 Previous cases included four women and one man, aged from 39 to 75 years (Table 1). The majority of the lesions, as ours, were located in the parotid gland with one exception in the hard palate.…”

“…Review of the literature.Age, sexLocalisationTakeda et al 1999 18 62-year-old manParotid48-year-old womanHard palateKajor et al 2006 16 75-year-old womanParotidMerino et al 1977 17 74-years-old womanParotid39-years-old womanParotidPresent case47-years-old womanParotid …”

Schwannomalike Mixed Tumor of the Parotid Gland

“…Immunohistochemical and sometimes ultrastructural examinations may prove helpful in cases of atypical and doubtful histopathologic pictures. 8,9 Kajor et al ACTA CYTOLOGICA Volume 50 Number 5 September-October 2006 …”