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A malignant proliferating trichilemmal tumor (MPTT) is thought to represent the malignant counterpart of a benign proliferating trichilemmal cyst, a keratin-filled lesion that derives from the outer hair root sheath. The clinical appearance of MPTTs does not always correlate with their histopathologic behavior, emphasizing the need for biopsy and histopathological analysis. Here, we present a 46-year-old African American woman who was evaluated for an ostensibly benign cyst on her scalp that was diagnosed as an MPTT following histopathological examination. She was treated with simple surgical resection that was flush with the cyst margins, followed by Mohs surgery to ensure complete resection. As immunohistochemistry (IHC) has often been used to characterize MPTTs, we also review the various IHC markers reported in the literature., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2021, Joshi et al.)

Verrucous xanthoma is a benign histiocytic lesion of macrophage derivation. We describe a woman with a non-mucosal verruciform xanthoma located on her right thumb and review the features of patients with verruciform acral-associated xanthoma. A 69-year-old woman presented with a lesion on her right thumb of eight years duration that had been previously treated with liquid nitrogen cryotherapy without resolution. An initial biopsy was consistent with the surface of a callous. A second biopsy demonstrated a verruciform xanthoma. The patient elected to apply lactic acid 12% twice daily and pare the lesion with a pumice stone once weekly; this resulted in flattening of the xanthoma-associated hyperkeratosis. Acral verruciform xanthoma has, albeit rarely, been described on the hands and feet of individuals. Including the patient in this report, six individuals have been reported with verrucous xanthoma on the hands and 12 individuals have been reported with a verrucous xanthoma on the feet. Verruciform xanthoma most commonly occurs on the oral mucosa. Genital lesions are also a frequent site. Acral-distributed verruciform xanthoma is rare; we propose that a verruciform xanthoma that occurs on acral sites be referred to as a verruciform acral-associated (Vacas) xanthoma., Competing Interests: Dr. Philip R. Cohen is a consultant for ParaPRO., (Copyright © 2021, Joshi et al.)

Galli-Galli disease (GGD) is a rare genodermatosis that is an acantholytic variant of Dowling-Degos disease that presents as lentigo-like macules/papules with progressive reticulated hyperpigmentation. Heat, sweat, ultraviolet light exposure, and topical retinoids have been reported to exacerbate the lesions associated with GGD. Here, we present a 77-year-old woman with end-stage renal disease and GGD who reported a worsening of lesions during the summer months and following hemodialysis treatment. Despite the severity of her lesions following dialysis, she refused treatment with isotretinoin out of concern for its side effect profile. In this case report, we discuss some available treatment options for GGD and review the exacerbating factors for GGD currently reported in the literature., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2021, Joshi et al.)

Granuloma annulare (GA) is a common inflammatory skin condition that manifests as annular skin colored to erythematous papules and plaques. Disseminated GA is a subtype of GA that presents with diffuse cutaneous involvement. While topical and intralesional corticosteroids and phototherapy have been used as therapies for GA, there is no consensus on the best course of treatment for GA. Apremilast is a phosphodiesterase 4 (PDE4) inhibitor that has been Food and Drug Administration (FDA) approved for psoriasis, psoriatic arthritis, and oral ulcers associated with Behcet's disease; apremilast has also shown promise off-label for other inflammatory skin conditions. Here, we present the case of a woman in whom apremilast use led to an almost complete resolution of her disseminated GA. Our patient tolerated apremilast well and reported no side effects. We also review the literature on the use of apremilast in other patients with GA., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2021, Joshi et al.)