Excerpt from Cylindroma

Synonyms, Key Words, and Related Terms: turban tumor, tomato tumor, Brooke-Spiegler syndrome, BSS, benign adnexal tumor, dermal eccrine cylindroma, Spiegler's tumor, epithelioma adenoides cysticum of Brooke, Ancell-Spiegler cylindroma, adenoid cystic carcinoma, ACC, cribriform carcinoma

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Background

Cylindromas are benign skin appendage tumors. They can be seen in conjunction with eccrine spiradenomas and trichoepitheliomas. Cases of spiradenocylindromas, demonstrating characteristics of both spiradenoma and cylindroma in the same tumor mass, have also been observed, suggesting similar derivation of both tumors.

They most commonly occur on the head and neck as solitary or multiple tumors. Solitary cylindromas occur sporadically and typically are not inherited. Multiple tumors are observed in an autosomal dominantly inherited manner. When nodules enlarge and coalesce on the scalp, they form the distinctive turban tumor feature.

Malignant cylindromas are very rare. Malignant transformation may develop within solitary cylindromas, or they may complicate the multiple variant (more common).

Pathophysiology

Cylindromas are appendage tumors previously thought to be of apocrine differentiation, thus differentiating them from spiradenomas, appendage tumors previously thought to be of eccrine differentiation. While phenotypic features differ between cylindromas and spiradenomas, recent studies have shown immunohistological and cytomorphological overlap, with both tumors exhibiting apocrine, eccrine, secretory, and ductal features. Therefore, the cellular origin of cylindromas remains unknown. Cylindromas are most likely a very primitive sweat gland tumor differentiating toward either the eccrine or apocrine line.

Brooke-Spiegler syndrome (BSS) has been described as an autosomal dominant disease characterized by the development of multiple skin appendage tumors such as cylindromas, trichoepitheliomas, and spiradenomas, with a variable preponderance of any of the aforementioned subsets. Other lesions reported with BSS include parotid basal cell adenomas, organoid nevi, syringomas, and basal cell carcinomas. Despite variable phenotypic expressions of a predominant tumor in BSS, the gene responsible for multiple cylindromas, CYLD, is localized to band 16q12-q13. The mechanism of genotypic similarity and phenotypic variance is not yet understood.^{1, 2}

In 2006, Zhang et al³ reported a large consanguineous Chinese family with BSS demonstrating intrafamily phenotypic variability. Upon examination, some persons only manifested discrete, small, skin-coloured growths, while the proband manifested an expansion of multiple large growths on the nose and numerous dome-shaped papules on the scalp. Biopsy showed both trichoepitheliomas and cylindromas in the affected persons. By sequence analysis, Zhang et al identified a recurrent mutation 2272C→T (R758X) of the CYLD gene in the affected familial persons that had been previously identified in other ethnic kindreds with familial cylindromatosis.

In 2007, Stegmeier et al⁴ noted that the CYLD gene encodes a deubiquitinating enzyme. The enzyme removes Lys-63–linked ubiquitin chains from I-kappaB kinase signaling components. By this mechanism, the enzyme inhibits NF-kappaB pathway activation. They demonstrated that CYLD is also required for the cell's timely entry into mitosis. Consistent with a cell-cycle regulatory function, CYLD localizes to microtubules in interphase and the midbody during telophase. CYLD's protein levels decrease as cells exit from mitosis. Stegmeier et al identified the protein kinase Plk1 as a potential target of CYLD as a regulator of mitotic entry, and they suggested this because of the physical interaction and similar loss-of-function and over-expression phenotypes.

These findings raise the possibility that, as with other genes that regulate tumorigenesis, CYLD has both tumor-suppressing (apoptosis regulation) and tumor-promoting activities (enhancer of mitotic entry). They suggested that this additional function of CYLD could provide an explanation for the benign nature of most cylindroma lesions.

Massoumi and Paus⁵ and explained the manner in which CYLD interferes with tumor necrosis factor-alpha or Toll-like receptor–mediated signaling and with JNK or NF-kappaB-dependent p65/50 signaling to limit inflammation. Additionally, the manner by which CYLD interferes with activation of the proto-oncogene BCL3 and with cyclin D1 expression to limit tumorigenesis was also explained. Finally, the researchers discussed how tumor growth-promoting agents or UV light and inflammatory mediators may activate CYLD.

Frequency

United States

Cylindromas are uncommon. The exact incidence is not known.

International

The exact international incidence is not known.

Mortality/Morbidity

Most cylindromas remain benign; however, at least 14 reports have described malignant transformation. Multiple cylindromas can cover the entire scalp and cause the disfiguring turban tumor appearance, which necessitates extensive reconstructive surgery.

Race

No racial disparity is reported.

Sex

The incidence of cylindroma is more common in females than in males. Female-to-male ratios of 6:1 and 9:1 have been reported.

Age

Solitary cylindromas are lesions that affect middle-aged and elderly persons. Multiple, inherited cylindromas usually begin in early adulthood and increase in size and number throughout life.

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