This education series for dermatologists is presented by the Weill Cornell Comprehensive Dermatopathology Service.
A 50-year-old woman presented with recent pigmentation of the left big toenail. A biopsy was performed (Figures A-D). This condition is caused by:
a. Hortaea werneckii
b. Malassezia globosa
c. Trichophyton rubrum
d. Candida parapsilosis
A 90-year-old man presented with a verrucous scrotal papule. A biopsy was performed (Figures A-C). The best diagnosis is:.
a. Condyloma acuminatum
b. Verruciform xanthoma
c. Squamous cell carcinoma in situ
d. Verrucous carcinoma
To learn the answers, go to page 2
Case 1: A
Tinea nigra is a relatively uncommon superficial mycosis caused by the pigmented (dematiaceous) fungus Hortaea werneckii. The infection most commonly affects children and young adults who travel to or live in tropical and subtropical climates in Central America, South America, Africa, and Asia. Direct contact with the fungus is required with hyperhidrosis and skin trauma being contributing factors. Infected individuals manifest with asymptomatic pigmented palmar or plantar macules or patches, although other areas such as the digits and interdigital spaces can be affected. The organism grows as pigmented yeast forms that can transform into a mold and is usually limited to the stratum corneum. Tinea nigra usually responds rapidly to therapy and generally does not recur.1-3
1. Bonifaz A, Gómez-Daza F, Paredes V, Ponce RM. Tinea versicolor, tinea nigra, white piedra, and black piedra. Clin Dermatol. 2010;28(2):140-145.
2. Perez C, Colella MT, Olaizola C, Hartung de Capriles C, Magaldi S, Mata-Essayag S. Tinea nigra: report of twelve cases in Venezuela. Mycopathologia. 2005;160(3):235-238.
3. Bonifaz A, Badali H, de Hoog GS, et al. Tinea nigra by Hortaea werneckii, a report of 22 cases from Mexico. Stud Mycol. 2008;61:77-82.
Case 2: B
Verrucous xanthoma, or so-called verruciform xanthoma, is an uncommon benign lesion that can appear as a warty, polypoid, papillomatous, or sessile lesion most commonly on the oral mucosa, scrotum, and penis in middle-aged men. At times the lesions can occur elsewhere, specifically on the perineum.1 Some predisposing factors include chronic lymphedema or an epidermal nevus.2 Histologically, this entity is characterized by verrucous epidermal hyperplasia with endophytic invaginations that are associated with a very distinct and orderly pattern of almost wedge-shaped hypereosinophilia of the cytoplasms of the keratinocytes. There are numerous lipid laden macrophages present within the superficial corium.
1. Stiff KM, Cohen PR. Vegas (verruciform genital-associated) xanthoma: a comprehensive literature review. Dermatol Ther (Heidelb). 2017;7(1):65-79.
2. Hegde U, Doddawad VG, Sreeshyla H, Patil R. Verruciform xanthoma: a view on the concepts of its etiopathogenesis. J Oral Maxillofac Pathol. 2013;17(3):392-396.
Dr Magro is the director of dermatopathology at Weill Cornell Medicine in NewYork, NY. For more information, please visit www.weillcornelldermpath.com.
Dr Saab is a pathology fellow at Memorial Sloan Kettering Cancer Center in NewYork, NY.
Dr Gaan is with the department of dermatology at Weill Cornell Medicine in New York, NY.
Disclosure: The authors report no relevant financial relationships.