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  • Nuchal-type Fibroma of the Coccyx: DISCUSSION

This case is rare in that it occurred in an uncommon extranuchal site, and interesting in that nuchal-type fibroma was recently described. Cli­nically, this case resembled lipoma, but physical examination revealed that the lesion had more dense tissue than lipomas. And it had morphologi­cally distinct features from other fibrous tumors.

In 1988, Enzinger and Weiss first described nuchal-type fibroma as a rare fibrous growth oc­curring chiefly in the interscapular and paraspinal regions. Michal et al described the clinicopatho- logic features of 52 cases of nuchal-type fibroma in 1999. The ages of patients ranged from 3 to 68 years, and according to the report nuchal-type fibroma occurs predominantly in males. The nuchal region is the most commonly affected area, but about one-third of cases affected extranuchal sites. Extranuchal sites most often involved the back or scapular region, shoulder, and face. However, other sites of involvement were the forearm, anterior neck, knee, and truncal region.

Macroscopically, nuchal-type fibromas are poorly circumscribed masses with a hard consistency and off-white color. Microscopically, the process was paucicellular and composed of thick, haphazardly arranged collagen fibers. In the central parts of the lesions, the collagen bundles often intersected and had a vaguely lobular architecture. The process was predominantly located in the subcutis, but can exhibit infiltration and entrapment of the underly­ing fatty tissue or skeletal muscle. Entrapped islands of adipose tissue were seen in most nuchal- type fibromas, and they contained entrapped peripheral nerve twigs, sometimes exhibiting a splayed appearance similar to that of a traumatic neuroma. A delicate network of elastic fibers was often observed between the collagen fibers. Extra- nuchal nuchal-type fibromas were morphologically identical to the examples involving the nuchal region. Our case was consistent with these general findings of nuchal-type fibroma.
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Histologic examination of normal tissue from the nuchal region showed thick collagen fibers in the deep dermis reminiscent of those seen in nuchal- type fibroma. However, only the nuchal-type fibromas showed lobulation of the collagen fibers, encasement of adnexal structures, and extensive involvement of the subcutis, resulting in a mass effect. Also, neuroma-like proliferations of the peripheral nerves were not seen in any of the normal tissue specimens. Nuchal-type fibroma should be distinguished from other fibrous tumors and tumor-like conditions, especially the desmoid- type fibromatosis, circumscribed storiform colla- genoma, connective tissue nevus, desmoplastic fibroblastoma, elastofibroma, and fibroma of tendon sheath. Nuchal-type fibroma differ from these tumors in that nuchal-type fibromas are less cellular, poorly circumscribed, and display collagen tissue by bundles of fibers. Treatment of nuchal-type fibroma is surgical excision, but recurrence is common.

Associated conditions of nuchal-type fibroma have been reported recently. Diabetes is strongly suspected of predisposing the condition of nuchal- type fibroma. In one series, described previously, 44% of patients with nuchal-type fibroma had diabetes. It suggests that nuchal-type fibroma with diabetes may occur by tumor-like changes in fibrous tissues, like a link between diabetes and scleredema. And, some authors suggested by their case reports that nuchal-type fibroma is related to Gardner’s syndrome. Gardner syndrome, caused by mutations in the adenomatous polyposis coli (APC) gene, is characterized by polyposis coli, osteomas, and various soft-tissue tumors. However, our case did not reveal these associated conditions. The coccygeal area is usually exposed to repeated minor traumas in normal individuals. Thus, this case of the coccygeal location suggests that nuchal-type fibroma can be an abnormal fibrous change against repeated trau­mas. But, these theories are not yet clearly under­stood. Therefore, further studies are needed for the etiology of nuchal-type fibromas. buy cialis soft tabs

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