Stroma-poor Warthin s tumor with significant oncocytic hyperplasia: case presentation and considerations regarding its histogenesis

Vol. 57 No. 2 Suppl., 2016
This supplement was not sponsored by Outside Organizations.

ROMANIAN JOURNAL of MORPHOLOGY and EMBRYOLOGY

Hiroo Kawano, Tokuhiro Kimura, Nami Kikuchi, Aya Ishii, Eiji Ikeda

Although Warthin s tumor is one of the common tumors of the salivary glands, Warthin s tumors with a prominent component of nodular oncocytic hyperplasia reminiscent of oncocytoma are rare. Here we report such a tumor, measuring 3 cm in diameter, found in the parotid gland of an 81-year-old man. Histologically, approximately 70% of the mass was a component of nodular oncocytic proliferation, and the remaining portion was a component of conventional Warthin s tumor. We performed immunohistochemical analysis to explore what factors determined the morphogenesis of the two components in the single mass. Cytokeratin (CK) 5/6-positive tumor cells, which represent basal cells, were aligned in a layer in the conventional Warthin s tumor component, whereas they were localized around blood vessels in the nodular oncocytic hyperplasia component. Immunostaining for CD34 showed that capillaries were sparsely present beneath the bilayered epithelia in the former component, while blood vessels resembling sinusoids separated the trabeculae of the tumor cells in the latter component. Ki-67 labeling index was slightly higher in the latter component. Double immunostaining for CK5/6 and Ki-67 revealed that most of Ki-67-positive proliferating tumor cells were CK5/6-positive, suggesting that CK5/6-positive population contained proliferative progenitor cells of the tumor. These findings imply that the regional difference in the distribution pattern and proliferative activity of CK5/6-positive putative progenitor cells along with the difference in the pattern of vascular network occurred during the tumorigenic process of the tumor and determined one region to become conventional Warthin s tumor morphology and the other to become nodular oncocytic hyperplasia.

Corresponding author: Tokuhiro Kimura, MD; e-mail: tkimura@yamaguchi-u.ac.jp

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ROMANIAN JOURNAL of MORPHOLOGY and EMBRYOLOGY

Jose-Fernando Val-Bernal, Sandra Hermana

Spindle cell lipoma located in the dermis is uncommon. The plexiform variant of this tumor is rare. In fact, only six cases of this variant have been described previously. We report herein a case of dermal plexiform spindle cell lipoma with prominent myxoid matrix. A 47-year-old male patient presented with a solitary, 2.2 cm-cutaneous mass in the right buttock region that had slowly increased in size for over one year. The dermal lesion was characterized by a mixture of mature adipocytes, spindle shaped cells and inconspicuous ropey collagen bundles in a mucinous background. This lesion showed a fascicular and plexiform pattern with adipocytes irregularly arranged, predominant in the depth of the lesion. Immunohistochemically, the spindle cells were positive for CD34, factor XIIIa, and vimentin, and negative for retinoblastoma protein, claudin-1, GLUT-1, epithelial membrane antigen, neurofilament protein, and Sox-10. S100 protein stained a thinned cytoplasmic rim of mature adipocytes and labeled about 25% of spindle cells in the most superficial areas. A review of the seven cases published, including the present report, revealed that there were five females and two males. Most cases located in the thigh-groin-buttock area. The age of the patients ranged from 32 to 58 years with a mean of 45.7 years. Clinical diagnosis suggested a lipomatous or neural tumor in six cases. The main differential diagnosis includes dermal intraneural plexiform neurofibroma and purely intradermal monophasic plexiform spindle cell nevus.

Corresponding author: Jose-Fernando Val-Bernal, MD, PhD; e-mail: apavbj@humv.es

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