Clear cell hidradenoma: a mimic of metastatic clear cell tumors.Arch Pathol Lab Med. 2005 May;129(5):e113-6.

Clear cell hidradenoma is a benign skin appendage tumor that may mimic conventional-type renal cell carcinoma. Histologically, clear cell hidradenoma contains small ductular lumens, focal apocrine and squamoid change, and a less prominent vascular pattern than renal cell carcinoma. Furthermore, immunohistochemical studies can aid in distinguishing the 2 tumors. Knowing the cytologic features of primary skin adnexal neoplasms helps distinguish them from cutaneous metastases, which are more commonly referred for fine-needle aspiration biopsy evaluation. Detailed clinical history, physical findings, and ancillary studies are essential for correct diagnosis and categorization of these tumors. We report the rare case of a patient with renal cell carcinoma who underwent excision of an axillary clear cell hidradenoma, which was clinically suggestive of cutaneous metastatic disease.

Clear-cell hidradenoma of the forearm in a young boy.Pediatr Dermatol. 2005 Sep-Oct;22(5):450-2.

We treated a 5-year-old boy with clear-cell hidradenoma of the forearm. Our literature search found only one previous report of this disease occurring during the first decade of life, and the present patient is the first with involvement of the limbs. This presentation demonstrates that clear-cell hidradenoma needs to be considered in the differential diagnosis of cutaneous tumors even in young children, which is of interest because malignant transformation can occur.

Clear cell hidradenoma of the skin-a third tumor type with a t(11;19)--associated TORC1-MAML2 gene fusion. Genes Chromosomes Cancer. 2005 Jun;43(2):202-5.

Recent studies have shown that the t(11;19)(q21;p13) translocation in mucoepidermoid carcinomas and benign Warthin's tumors results in a fusion of the N-terminal CREB-binding domain of the cAMP coactivator TORC1 (a.k.a. MECT1 and WAMTP1) to the Notch coactivator MAML2. Here we show that a third tumor type, clear cell hidradenoma of the skin, also expresses this gene fusion. RT-PCR analysis of a clear cell hidradenoma with a t(11;19)(q21;p13) translocation revealed expression of a TORC1-MAML2 fusion transcript consisting of exon 1 of TORC1 fused to exons 2-5 of MAML2. Because the fusion was only detected in a single case, the frequency of this aberration in clear cell hidradenomas remains unknown. These results demonstrate that the t(11;19) in mucoepidermoid carcinoma, Warthin's tumor, and clear cell hidradenoma targets the same genes and results in identical gene fusions, indicating that at least subgroups of these glandular tumors evolve through activation of the same molecular pathways.