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hyalinizing clear cell carcinoma

Tuesday 10 May 2011

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Definition: Hyalinizing clear-cell carcinoma (HCCC) is a rare, low-grade salivary gland tumor with distinctive clear-cell morphology and pattern of hyalinization as well as focal mucinous differentiation.

However, histological overlap exists with other salivary gland tumors, such as epithelial-myoepithelial carcinoma (EMCa), salivary myoepithelial carcinoma, and mucoepidermoid carcinoma (MEC).

Microscopy

HCCC consist of cells with abundant clear cytoplasm, arranged in cords, trabeculae or clusters in a hyalinized stroma.

Nuclear pleomorphism is usually minimal and mitoses are infrequently seen.

Owing to their glycogen content, which explains the "clear" appearance under the microscope, tumour cells stain with PAS.

Immunochemistry

Immunostains for S100 and smooth muscle actin (SMA) are typically negative, but positive for cytokeratins and epithelial membrane antigen (EMA).

HCCCs typically have a recurrent chromosomal translocation, t(12;22), involving the genes EWSR1 and ATF1.[5] The same translocation is seen in clear cell sarcoma.

The histologic differential diagnosis includes mucoepidermoid carcinoma (clear cell variant), acinic cell carcinoma (clear cell variant), epithelial-myoepithelial carcinoma and metastatic clear cell carcinoma.

Molecular biology

- EWSR1-ATF1 fusion gene in hyalinizing clear-cell carcinoma of salivary gland. (#21484932#)

  • The presence of EWSR1-ATF1 fusion in most HCCCs reliably separates these tumors from its histological mimics.
  • The distinction from mucoepidermoid carcinoma (MEC) is particularly important, as conventional MEC grading schemes overgrade these indolent HCCCs, potentially impacting on treatment.

Open access references

- Hyalinizing clear cell carcinoma: report of eight cases and a review of literature. O’Sullivan-Mejia ED, Massey HD, Faquin WC, Powers CN. Head Neck Pathol. 2009 Sep;3(3):179-85. PMID: #20596970# [Free]

- Hyalinizing clear cell carcinoma: case series and comprehensive review of the literature. Solar AA, Schmidt BL, Jordan RC. Cancer. 2009 Jan 1;115(1):75-83. Review. PMID: 18980290 [Free]

References

- EWSR1 Genetic Rearrangements in Salivary Gland Tumors: A Specific and Very Common Feature of Hyalinizing Clear Cell Carcinoma. Shah AA, Legallo RD, van Zante A, Frierson HF Jr, Mills SE, Berean KW, Mentrikoski MJ, Stelow EB. Am J Surg Pathol. 2013 Feb 15. PMID: #23426124#

- EWSR1-ATF1 fusion is a novel and consistent finding in hyalinizing clear-cell carcinoma of salivary gland. Antonescu CR, Katabi N, Zhang L, Sung YS, Seethala RR, Jordan RC, Perez-OrdoƱez B, Have C, Asa SL, Leong IT, Bradley G, Klieb H, Weinreb I. Genes Chromosomes Cancer. 2011 April PMID: #21484932#