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 manifestations of the inherited disorder, CYLD cutaneous syndrome (CCS), and 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 spiradenocarcinoma tumors that develop in individuals afflicted with the CYLD cutaneous syndrome. CCS is an inherited disorder that commonly involves the development of multiple but on occasion a single or few tumors that closely resemble, and may be confused with, the sporadic SA and SAC tumors described here. CCS spiradenoma and CCS spiradenocarcinoma tumors must be distinguished from the sporadic SA and SAC tumors reviewed here in order to afford genetic counseling to individuals with CCS as well as to the close family members of these individuals. Currently, SA and SAC are usually treated by complete excision making sure that no tumor cells are left behind at the surgical site. This is particularly important in SAC where the incomplete surgical removal of all tumor cells may result in recurrence of the tumor at the surgical site and/or its metastasis to the local lymph nodes draining the surgical site and/or to distant tissues. In addition to surgical resection, some cases of SAC tumors have been treated with adjuvant therapy that includes radiotherapy and/or chemotherapy. It is not clear that these adjuvant treatments improve patient prognoses. Further studies are needed to determine the best treatment(s) for localize SA, localized SAC, and, in particular, metastatic SAC tumors.
Presentation Spiradenoma tumors occur in individuals of various ages but tend to develop in middle-aged and elder adults (e.g. in a study of 27 patients, the median age at diagnosis was 62 years). However, cases have been reported in children as young as 2 years. These tumors usually present as a solitary, sometimes painful, slowly growing, 1–2 cm (i.e. centimeters), gray-to-pink nodules that lie underneath the skin's epidermis in the head, neck, trunk, arms, or legs. However, these nodules have been reported to be as large as 6 cm and to occur in other hair follicle-containing cutaneious sites such as the vulva, breast, and breast nipple. Areas of the skin that do not have hair follicles (e.g. palms of the hands and soles of feet) do not develop these nodules. Less than 2% of cases present with more than one nodule; the multiple nodules in SA tend to array in a linear, blaschkoid (i.e. V-, U-, or inverted U-shaped), or zosteriform (i.e. belt- or girdle-shape tracking an area of skin served by a sensory nerve) patterns. Giant vascular eccrine spiradenomas are larger (> 2 cm) and more highly vascular variants of SA that usually develop at the same cutaneous sites as SA but have also been reported to occur in the abdomen and scrotum. No malignant giant vascular SA has been described in the literature to date (2021). A 2011 review of 182 cases reported that spiradenocarcinomas were diagnosed in individuals 8–89 years old (mean 57.4 years). These SAC tumors developed in SA tumors that had existed for 0–720 months (mean 168.5 months); 14.4% of individuals were diagnosed with multiple carcinoma lesions. (Multiple SAC lesions may appear as a nodule associated with smaller satellite nodules.) The lesions occurred on the trunk (32.3% of cases), limbs (31.3%), head or neck (30.7%), and genitalia (1.6%). These individuals presented with lesions that began to show abnormal growth (82.6% of cases), pain (47.7% of cases), and/or ulcerations (38.7% of cases). In earlier studies, SAC tumors were reported to varied in size with 40% being larger than 5 cm and the majority not having metastasized; the sites to which these lesions metastasized were most commonly to lymph nodes near to the SAC or, rarely, distant tissues such as the lung, liver, brain, spinal cord, bone, skin, and breast.
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