Steatocystoma multiplex is a rare disease consisting of multiple cysts that erupt across the chest, arms, armpit, and neck, usually inherited in an autosomal dominant manner . These lesions are largely asymptomatic, but may erupt and secrete an oily substance if the cyst is close to the skin’s surface . Many of the features of this condition overlap with a variety of diseases such as eruptive vellus hair cyst (EVHC) and acne vulgaris. It is therefore important to differentiate, as the work-up and treatment differ greatly [2,3]. This case report outlines a presentation of steatocystoma multiplex to draw attention to the unique clinical features of this rare condition.
A 47-year-old woman with a past medical history that was only significant for recurrent skin infections presented for a routine mammogram with no symptoms or concerns.
The patient’s screening mammogram was performed (Figures: 1, 2), and countless oil cysts are visualized in both breasts, mainly in the medial aspect. The patient had a diagnostic mammogram with focused bilateral breast ultrasound, which showed multiple oval anechoic cystic masses consistent with mammographic findings of multiple oil cysts. A follow-up ultrasound was done (Figure 3), which showed a circumscribed, avascular oil cyst.
Upon inspection of the patient card, she had no history of breast trauma, previous breast procedures, or breast symptoms. The patient was contacted after her imaging results. She denied any significant medical or family history of breast or skin pathology at this time. She did note that, since early adulthood, she has had multiple “lumps” on her torso, chest, and inner arms continuously, representing subcutaneous cysts that slowly increased in number over time (Figure 4). She also notices a subcutaneous cyst on her chest that will occasionally erupt and bleed out oily fluid. She denied any other associated symptoms or concerns regarding her cysts and says she is the only one in her family with these symptoms.
The patient’s primary care physician has been contacted regarding the findings and will continue to monitor her symptoms on an outpatient basis.
Steatocystoma multiplex is an uncommon benign condition that has overlapping clinical features with a variety of other pathologies. Cysts often appear subcutaneously on the arms, armpit, and trunk from puberty onwards. It is important to be aware of the unique features of this condition in order to distinguish it from other potentially more serious diseases. By correctly identifying this diagnosis, patients can also be saved from unnecessary psychological distress, unnecessary effort and hospital costs. This condition has overlapping features with diseases such as eruptive vellus hair cysts, trichofolliculoma, and syringoma [4,5]. It can also resemble lipomas, fat necrosis, galactoceles, and epidermal inclusion cysts, among many other dermatological conditions. This is why, if the case is not clinically clear, further histological evidence may be warranted .
This condition involves small, non-painful subcutaneous cysts most commonly found on the trunk, upper extremities, and armpit, beginning at puberty [1,7]. The histological features of steatocystoma multiplex consist of stratified squamous epithelial walls with an irregularly lined eosinophilic center . While many cases appear to be sporadic mutations, there is a strong association with the KRT17 gene, which has an autosomal dominant pattern of inheritance. Other mutations have also been associated with this condition, including N92S, R94H, and R94C . It does not appear to have an increased prevalence in any specific gender or ethnic group . Imaging findings in steatocystoma multiplex include mammography showing multiple oil cysts (small, round, circumscribed cysts with a central fat density). Ultrasound shows multiple anechoic cysts with posterior acoustic enhancement.
If the patient’s clinical presentation is suspicious for multiple conditions, steatocystoma multiplex can be differentiated using histological features. One study analyzed the histological features of 67 cases with steatocystoma multiplex and found that all cases had an eosinophilic cuticle with no glandular layer, with a minority of cases also containing hair follicles, keratin and smooth muscle. . The walls of the cysts are multilayered squamous epithelium with an uneven eosinophilic rim in the center .
Once the diagnosis of steatocystoma multiplex is confirmed, patients do not require further imaging or workup, as the condition is benign and requires no intervention. However, patients often experience psychological problems because of their symptoms . If the patient wishes to continue further treatment of cysts, there are several treatment modalities, with no specific gold standard or preferred option. Rather, treatment should be tailored to the patient’s individual presentation . Options include cryotherapy, aspiration, laser therapy, or surgical resection. Treatment is also aimed at preventing secondary skin infections.
Steatocystoma multiplex is a rare condition with unknown prevalence in the population. It has no gender or ethnic preference and is due to a sporadic or autosomal dominant mutation with many different genes associated.
Although this condition is benign, it is important to have a clinical suspicion for this condition as it overlaps clinical features with a wide variety of other dermatological conditions that require different treatment modalities. In addition, it is important to note that this condition is benign and does not require further workup. A variety of treatment options focused on cosmetic changes and the prevention of infection are available if the patient experiences psychological distress as a result of symptoms.