Spiradenomas (SA) are rare, benign cutaneous adnexal tumors that may progress to become their malignant counterparts, i.e. spiradenocarcinomas (SAC). Cutaneous adnexal tumors are a group of skin tumors consisting of tissues that have differentiated (i.e. matured from stem cells) towards one of the four primary adnexal structures found in normal skin: hair follicles, sebaceous sweat glands, apocrine sweat glands, and eccrine sweat glands. SA and SAC tumors were regarded as eccrine gland tumors and termed eccrine spiradenomas and eccrine spiradenocarcinomas, respectively. However, more recent studies have found them to be hair follicle tumors and commonly term them spiradenomas and spiradenocarcinomas, respectively. Further confusing the situation, SA-like and SAC-like tumors are also 1) manifestations of the inherited disorder, CYLD cutaneous syndrome (CCS), and 2) have repeatedly been confused with an entirely different tumor, adenoid cystic carcinomas of the salivary gland. Here, SA and SAC are strictly defined as sporadic hair follicle tumors that do not include the hereditary CCS spiradenomas and heridtary spiradenocarcinoms of CCS or the adenoid cystic carcinomas. SA tumors usually occur as slow-growing, single, small, nodular lesions located in the skin of the head, neck, or trunk. SAC tumors develop from benign SA tumors or in very rare cases begin as malignant tumors. SA and SAC tumors must be distinguished from the spiradenoma and spiradenocaricnoma tumors that develop in individuals afflicted with the CYLD cutaneous syndrome.
It is proposed that the blockade of NF-κBs actions prolongs cell survival, stimulates high rates of cell growth, and perhaps has other effects which contribute to the formation and/or progression of SA and SAC tumors. Diagnosis
SA and SAC tumors have been confused with leiomyoma, angiolipoma, granular cell tumor, basal cell carcinoma, squamous cell carcinoma, metastatic adenocarcinoma, and adenoid cystic carcinoma tumors; the giant vascular SA form of these tumors has been mistaken for a hemangioma, angiolipoma, calcifying epithelioma, neuroma, malignant melanoma, angiosarcoma, vascular malformation, and venous thrombosis. CT scans, FDG-positron emission tomography, and magnetic resonance imaging to detect 1) the shape and local invasiveness of these tumors and 2) the presence of metastases and 2) the clinical presentation of individuals of these tumors often suggest the correct diagnosis. However, definitive separation of SA, SAC, and giant vascular SA from the just cited lesions requires histopathological examinations. The diagnosis of SA versus SAC tumors is often suggested by their clinical presentations, e.g. rapid enlargement or onset of pain in a long-standing SA tumor strongly suggests that it has become a SAC. Findings that a known SA or undiagnosed tumor has areas of SA histology transitioning to SAC histology (see above Pathology section) is virtually diagnostic for SAC.The sporadic SA and SAC tumors reviewed here must also be distinguished from the very similar appearing SA-like and SAC-like tumors in individuals afflicted with the CYLD cutaneous syndrome. CCS is a familial disease uniformly associated with the inheritance of inactivating mutations in the CYLD gene.