This case highlights the importance of thorough clinical examinations from head to toe and the early diagnosis of trichilemmal cysts. We present a case of an incidentally discovered trichilemmal cyst in a 72-year-old patient who presented with acute kidney injury secondary to a urinary tract infection. In rare instances, these cysts can transform into malignant lesions. Therefore, clinicians should be aware of the potential for malignancy when diagnosing and managing trichilemmal cysts.

Trichilemmal carcinoma (TC) is a rare, low-grade, malignant adnexal tumor. It is usually less than 3 cm long and arises from the external root sheath of the hair follicle, most commonly in sun-exposed areas of the body. The treatment of choice is wide local excision with tumor-free margins. We present an 88-year-old male patient who presented with an incidental large, dry, fumigating mass on his scalp for a one-year duration requiring surgical excision. The mass, initially thought to be a benign sebaceous cyst, was a 12-cm trichilemmal carcinoma diagnosed based on the histopathologic features of the mass. The specimen was composed of keratinaceous material and necrotic debris. The viable tumor was consistent with atypical squamous proliferation. The mass was fully excised down to the scalp on the first encounter, leaving no further tissue to excise. The patient\'s scalp site remained clean and without bleeding or recurrence. Currently, there is an increasing incidence of trichilemmal carcinoma. The pathophysiology of this disease is still unclear. The radiation from the sun is one of the factors that causes the growth of the lesions due to its location and distribution. Trichilemmal cysts can also transform into malignant trichilemmal carcinomas due to the p53 deletion. TC has a non-aggressive course despite its aggressive histology. The prognosis is generally good as it has low metastatic potential, like cutaneous squamous cell carcinoma. However, TC with metastasis has a poor prognosis, and there is no consensus yet on treatment. For non-metastatic TC, simple surgical excision with adequate (0.5-1 cm) margins is an effective treatment. Different studies use different margins, and there is no consensus on the measurement for margin excision. Regular follow-up is recommended, but further studies regarding follow-up schedules are needed. Furthermore, despite the common use of chemotherapy in cases of malignant TC, only a limited number of studies have explored this treatment approach. Given the increasing incidence of the disease, we highly recommend more research to address this knowledge gap.

Pilar cysts are common benign cysts of follicular origin that typically arise in areas of skin containing dense hair follicles such as the scalp. Here we describe a unique case of a young woman who was found to have a pilar cyst on the dorsum of her hand, a rather atypical location given the relative lack of pilosebaceous units. This case illustrates the variability in pilar cyst presentation and the importance of considering a pilar cyst in the differential diagnosis of a patient presenting with a tumor of the dorsal hand.

This is the second article in a two-part series published in this journal, in which we examine the histopathological characteristics, as well as the differential diagnosis, of the main entities that present as cystic and pseudocystic structures in cutaneous biopsy. In this second article, we address ciliated cutaneous cysts, branchial cysts, Bartholin\'s cysts, omphalomesenteric cysts, thymic cysts, thyroglossal duct cysts, synovial cysts, and median raphe cysts, as well as mucocele, ganglion, and auricular and digital myxoid pseudocysts.

Pilar cysts are derived from the outer layer of the root sheath of hair follicles. They were conventionally thought to arise from hair-bearing skin like the scalp. However, this notion has been refuted recently. Pilar cysts of the hand are extremely rare, with only a few case reports in the literature. We report the case of a 40-year-old male patient, with no known medical co-morbidities, who presented with a swelling over his left thumb. It was occasionally painful, and caused difficulty in grasping objects. Physical examination revealed a 2.5 x 1.5 cm swelling over the volar aspect of the thumb, at the level of the proximal phalanx. MRI revealed the presence of a well-defined cystic lesion superficial to the flexor tendons. The possibility of an epidermal cyst was considered, and the patient was advised surgery in view of his symptoms and progression in the size of the swelling. He underwent excision of the lesion along with a segment of adherent skin. Histopathological examination of the lesion revealed the presence of a pilar cyst. The patient did not have recurrence of symptoms following surgery, and was found to be doing well at the three-year follow-up. This case report urges a re-thinking of the possible origins of pilar cysts from atypical locations.

Nevus of Ota or congenital oculodermal melanosis (ODM) is characterized by brown or blue/gray asymptomatic brown or blue/gray flat lesions of the skin, mucosae, episcleral/sclera, and uvea, which are located near the trigeminal nerve\'s ophthalmic and mandibular branches. The main ophthalmic complications are glaucoma and predisposition to uveal melanoma. \"trichilemmal cyst\" is also known as \"wen\" \"pilar cyst\" or \" isthmus catagen cyst\". It occurs in the scalp and mimics sebaceous cysts clinically. The swelling appears smooth in outline and is filled with cytokeratin. An unusual case of a 32-year-old male with both trichilemmal cyst and nevus of Ota, a 27-year-old female, and a 47-year-old male with nevus of Ota is discussed here.

Cystic structures represent one of the most common findings in dermatopathology. These encompass both cystic tumors and pseudocysts resulting from the accumulation of certain substances, such as mucin. In a two-part series (of which this is the first part), we have reviewed the principal types of cysts and pseudocysts that may be observed in cutaneous biopsies, examining their histopathological features and primary differential diagnoses. This first part encompasses infundibular cysts, eruptive dermoid cysts, pigmented follicular cysts, pilonidal cysts, tricholemmal cysts, milium cysts, hybrid cysts, bronchogenic cysts, as well as steatocystoma, hydrocystoma, and comedones.

Cutaneous cystic lesions (n = 35) were examined with optical coherence tomography. Cysts were visible as a hyporeflective roundish area with a clear margin; in some cases, the epidermis was thinned. Epidermal cysts, trichilemmal cysts, and hidrocystomas had a linear margin representing the epithelium of the cyst, whereas mucoid pseudocysts showed no linear margin. Trichilemmal and epidermal cysts presented with hyperreflective content that corresponds to keratin. By visualizing the margin and the content of the cyst, it was possible to differentiate between different types of cysts.
UNASSIGNED: Kutane zystische Läsionen (n = 35) wurden mit optischer Kohärenztomographie untersucht. Zysten waren sichtbar als hyporeflektive rundliche Raumforderung mit klarer Abgrenzung unter teils verdünnter Epidermis. Epidermalzysten, trichilemmale Zysten und Hidrozystome hatten einen linearen Rand, der das Zystenepithel darstellt, während mukoide Pseudozysten keinen linearen Rand aufwiesen. Trichilemmal- und Epidermoidzysten wiesen zudem einen hyperreflektiven Inhalt auf, welcher Keratin entspricht. Durch die Visualisierung des Randsaums und des Inhalts der Zyste war es möglich, zwischen verschiedenen Entitäten von Zysten zu differenzieren.

UNASSIGNED: Cysts, primarily epidermal and trichilemmal, are commonly seen in clinical practice. Rupture, infection, inflammation, and rarely malignant transformation may complicate the cysts. This study aims to analyze the clinicohistological features of cutaneous cysts.
UNASSIGNED: A retrospective review of patients with the diagnosis of cyst confirmed on histopathology over the past two years (2020-2021) was performed. Clinical details comprised of age, gender, site of involvement, size, duration, and associated symptoms. Histological examination included cyst wall lining, type of keratinization, complications like rupture, inflammation, foreign body giant cell reaction, calcification, and malignant change.
UNASSIGNED: A total of 324 cases with mean age of 37.9 years and equal gender distribution were identified. Most frequent diagnosis was epidermal cyst in 89.8%, followed by trichilemmal cyst in 8.9% of cases. Rare types included follicular hybrid cyst, verrucous cyst, vellus hair cyst, and steatocystoma. Most common complication was cyst rupture in 54.3% of epidermal cysts. Proliferating epidermal and proliferating trichilemmal cysts were noted in one and two cases, respectively. Two cases revealed malignancy arising in the wall of epidermal cyst.
UNASSIGNED: The retrospective study design and non-availability of follow-up data, especially for proliferating cysts and cysts with malignant transformation were the main limitations of this study.
UNASSIGNED: Histopathologic examination of excised cutaneous cysts is paramount in reaching accurate diagnosis of the type of cyst and associated secondary changes to enable appropriate management.

Background Cysts are common skin abnormalities that are mostly benign; however, sometimes malignant lesions may present clinically as cystic manifestations. Benign cutaneous cysts can be of different morphological types and their diagnosis relies on histological evaluations. The most common mode of treatment is surgical excision, which is curative. Methodology This is a retrospective cross-sectional study conducted at the Department of Histopathology, Chughtai Institute of Pathology, Lahore, Pakistan from 1st January 2020 to 31st December 2022. Non-probability consecutive sampling was done, and all the cases of benign cutaneous cysts were included. All cases were microscopically reviewed by two histopathologists, and variables like age, gender, site of the lesion, and histological diagnosis were noted. The data were analyzed using IBM SPSS Statistics for Windows, Version 29 (Released 2022; IBM Corp., Armonk, New York, United States). Results A total of 1160 recorded cases of benign cutaneous cysts were included. Overall gender distribution revealed males (n=489, 42.1%) and females (n=671, 57.8%). The age range was 3 to 91 years with a mean age of 37.56 ± 16.05 years. The three most common cysts were epidermal inclusion cysts (74.3%), trichilemmal cysts (15.1%), and dermoid cysts (6.3%). Other cysts were uncommon including hidrocystoma (1.9%), steatocystoma (0.3%), verrucous cysts (0.3%), comedones (0.6%), hybrid cysts (0.2%), milia (0.3%), and vellus hair cysts (0.2%). The most common site was back (23.5%) for epidermal inclusion cysts, scalp (74.4%) for trichilemmal cysts, and eye (33.8%) for dermoid cysts. Conclusion Benign cutaneous cysts have a broad morphological spectrum with a wide age range. Epidermal inclusion cysts, trichilemmal cysts, dermoid cysts, and hidrocystoma account for the four most common types. For each of the other cyst type, the prevalence was under 1%. Female gender predominated in epidermal inclusion cysts, trichilemmal cysts, and dermoid cysts while male gender was common in other cysts. Overall majority of the cysts presented in the head and neck area.