Rare presentations of common tumors can lead to late or incorrect diagnoses. As dermatologists, we provide a critical diagnostic and therapeutic role in the management of these tumors with rare presentations.The following cases are from patients seen in routine dermatology visits at the Central Utah Clinic in Provo, UT. This quiz represents cases that may present to any dermatologist and asks questions that would be critical in proper management. Can you make a diagnosis based on these presentations.  Answer KEYCase #1: Diagnosis: Arsenical Keratoses and SCC1. T 2. T 3. T 4. F 5. TCase #2: Diagnosis: Muir Torre Syndrome1. T 2. T 3. F (autosomal dominant) 4. T 5. FCase #3: Diagnosis: Post-operative/Eruptive Keratoacanthoma1. T 2. T 3. T 4. T 5. TCase #4: Diagnosis: Basal Cell Carcinoma1. F 2. T 3. T 4. F 5. FCase #5: Diagnosis: Merkel Cell Carcinoma 1. F 2. T 3. T 4. F 5. TCase #6: Diagnosis: Perineural Spread of a Squamous Cell Carcinoma1. F 2. F 3. T 4. T 5. F Suggested READINGGoldmann, G. “Squamous Cell Carcinoma.” eMedicine. Accessed December, 2005. DERM/topic401.htm>.Katoulis A., Bozi E., Stavrianeas N., Muir-Torre syndrome. Orphanet Encyclopedia. May 2004. http://www.orpha.net/data/patho/GB/uk-MuirTorre.pdf.GoldbergLH, Silapunt S, Beyrau K , Peterson S R, Friedman P, Alam M. Keratoacanthoma as a postoperative complication of skin cancer excision. J Am Acad Dermatol 2005 May;50:753-8.Ponti G, Ponz de Leon M. Muir-Torre syndrome. Lancet. Oncol, 2005 Dec;6(12):980-7.Kovarik CL, Stewart D, Bernard JJ. Lethal basal cell carcinoma secondary to cerebral invasion. J Am Acad Dermatol. 2005 Jan;52(1):149-51. Veness M, Perera L, McCour J, Shannon J, Hughes T, Morgan G, and Gebski V. Merkel cell carcinoma: improved outcome with adjuvant radiotherapy. New Zealand Journal of Surgery 2005; 75(5): 275.Watson K, Creamer D. Arsenic-induced keratoses and Bowen's disease. Clin Exp Dermatol. 2004 Jan;29(1):46-8.Lawrence N, Cottel WI. Squamous cell carcinoma of skin with perineural invasion. J Am Acad Dermatol. 1994 Jul;31(1):30-3.Wheeden, David. Skin Pathology. (2nd ed) London: Churchill Livingstone, 2002: 774-775.