Dermatology: Practical and Conceptual Quiz | Dermatol Pract Concept 2016;6(3):2 3 DERMATOLOGY PRACTICAL & CONCEPTUAL www.derm101.com The patient A 50-year-old Caucasian gentleman presented with a one- year history of a gradually enlarging pigmented lump on the right forearm. On examination there was a 1 cm blue-purple nodule, which was hard in consistency (Figure 1). A mobile dermal cystic component was palpated after lateral pressure. Further dermoscopic examination revealed a homoge- neous blue-purple pigmentation surrounded by a subtle brown hyperpigmentation and a central white area with fine linear whitish structures. No pigment network was noticed (Figure 2). Histopathological examination was performed to exclude melanoma. It revealed an ill-defined nodular dermal pro- liferation of spindle-shaped fibroblasts and myofibroblasts arranged as short intersecting bundles. There were multiple dilated vascular channels and numerous hemosiderin-laden macrophages (Figure 3). A slowly enlarging purple nodule on the arm Sheena Ramyead1, Salvador Diaz-Cano2, Lucia Pozo-Garcia3 1 Department of General Medicine, Homerton University Hospital, East London, UK 2 Department of Histopathology, King’s College Hospital, London, UK 3 Department of Dermatology, Lewisham and Greenwich NHS Trust, London, UK Citation: Ramyead S, Diaz-Cano S, Pozo-Garcia L. A slowly enlarging purple nodule on the arm. Dermatol Pract Concept 2016;6(3):2. doi: 10.5826/dpc.0603a02 Copyright: ©2016 Ramyead et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Corresponding author: Sheena Ramyead, MBBS, MRCP, 74 Regency Lodge, Adelaide Road, Swiss Cottage, London, NW3 5ED, UK. Tel. +44 7920517226. Email: Sheena.ramyead@gmail.com Figure 1. Well-defined, blue-purple nodule on right forearm. [Copy- right: ©2016 Ramyead.] Figure 2. Homogeneous bluish purple pigmentation under dermos- copy surrounded by a subtle brown hyperpigmentation and a central whitish area with fine shiny linear whitish structures. [Copyright: ©2016 Ramyead.] mailto:Sheena.ramyead@gmail.com 4 Quiz | Dermatol Pract Concept 2016;6(3):2 At least 20 different histological variants of dermatofi- bromas have been described with the aneurysmal subtype being unusual (2% of all cases) [6-8]. Aneurysmal derma- tofibroma, also known as aneurysmal fibrous histiocytoma (AFH) was initially described in 1981 [9]. It presents as single dark papules or nodules, most commonly located on the lower limbs, which occasionally grow quickly and may bleed. They are clinically alarming and are often confused with melanocytic or vascular neoplasms [10]. Dermoscopy shows homogeneous pigmentation with different hues from blue-purple to red-brown colors. The presence of fine whitish linear structures corresponding to fibrosis is commonly seen, but these findings are non-specific and an excision biopsy is mandatory to exclude melanoma [10,11]. A rainbow pattern initially described in Kaposi sarcomas [12] has also been reported in aneurysmal dermatofibromas [13]. It can only be observed under polarized dermoscopy and is a result of the passage of polarized light through increased dermal fibrosis. Histologically, AFH consists of blood-filled spaces lacking endothelium within the fibrohistiocytic tumor. Perl’s stain is positive, identifying stromal hemosiderin deposition, while the spindle cells are negative for endothelial (CD34) and melanocytic (S100) markers [6]. The pathogenesis is unknown, however, the blood is thought to represent extrava- sation of erythrocytes from capillaries. Important clinical differential diagnoses include malignant melanoma, heman- gioma and Kaposi’s sarcoma. What is your diagnosis? Answer and explanation Aneurysmal dermatofibroma Dermatofibromas are benign fibrous histiocytomas, rep- resenting the second most common cutaneous fibrohistiocytic lesion after acrochordons (skin tags). They present as firm, dome-shaped papules, which are commonly hyperpigmented and are primarily seen in adults on the lower extremities [1]. The dimpling of the skin with lateral compression or “Fitz- patrick’s sign” is considered by many to be pathognomonic for dermatofibromas. Despite the description of this sign in all major textbooks, not all dermatofibromas dimple (as in our case), and all that dimple are not dermatofibromas. The exact etiology of dermatofibromas is unknown, however, they have been associated with trauma and insect bites [2]. They are usually solitary, but cases of multiple synchronous lesions (eruptive dermatofibromas) have been reported, especially associated with autoimmune disorders, in particular, systemic lupus erythematosus, atopic eczema and human immunode- ficiency virus [3-5]. Histologically, dermatofibromas are characterized by a nodular dermal proliferation of spindled fibroblasts and myo- fibroblasts, arranged in intersecting fascicles with entrapment of thick collagen bundles in the superficial and mid dermis. There is hyperplasia of the epidermis with flat confluent rete ridges. The proliferating cells are positive for vimentin, factor XIIIa and CD68 and negative for CD34. Figure 3. Ill-defined dermal proliferation of spindle cells and blood vessels with numerous superficial siderophages (panel A, hematoxylin-eosin 40x). The spindle cells infiltrate around thick collagen bundles at the lesion periphery (panel B, HE 200x) and it shows dilated blood vessels and siderophages in the upper part (panel C, HE 400x). [Copyright: ©2016 Ramyead.] Quiz | Dermatol Pract Concept 2016;6(3):2 5 6. Calonje E, Fletcher CD. Aneurysmal benign fibrous histio- cytoma: clinicopathological analysis of 40 cases of a tumour frequently misdiagnosed as a vascular neoplasm. Histopathol- ogy 1995;26(4):323-31. PMID: 7607620. DOI: 10.1111/j.1365- 2559.1995.tb00193.x. 7. Kamino H, Reddy V, Pui J. Fibrous and fibrohisticocytic prolifera- tion of the skin and tendons. In: Bolognia J, Jorizzo J, Schaffer J, eds. Dermatology. 3rd ed. Philadelphia: Saunders, 2012:1962- 1963. 8. Luzar B, Calonje E. Cutaneous fibrohistiocytic tumours—an update. Histopathology 2010;56(1):148-65. PMID: 20055912. DOI: 10.1111/j.1365-2559.2009.03447.x. 9. Santa Cruz DJ, Kyriakos M. Aneurysmal (“angiomatoid”) fibrous histiocytoma of the skin. Cancer 1981;47(8):2053-61. PMID: 6261935 10. Zaballos P, Llambrich A, Ara M, Olazaran Z, Malvehy J, Puig S. Dermoscopic findings of haemosiderotic and aneurysmal derma- tofibroma: report of six patients. Br J Dermatol 2006;154(2):244- 50. PMID: 16433792. DOI: 10.1111/j.1365-2133.2005.06844.x. 11. Blum A, Jaworski S, Metzler G, Bauer J. Lessons on dermos- copy: Dermoscopic pattern of hemosiderotic dermatofibroma. Dermatol Surg 2004;30(10):1354-5. PMID: 15458535. DOI: 10.1111/j.1524-4725.2004.30409.x. 12. Cheng ST, Ke CL, Lee CH, Wu CS, Chen GS, Hu SC. Rainbow pattern in Kaposi’s sarcoma under polarized dermoscopy: a der- moscopic pathological study. Br J Dermatol 2009;160(4):801-9. PMID: 19067686. DOI: 10.1111/j.1365-2133.2008.08940.x. 13. Padilla-Espana L, Fernandez-Canedo I, Blazquez-Sanchez N. Fast-growing pigmented nodular lesions. Actas Dermosifil- iogr 2015;106(6):505-6. PMID: 25770848. DOI: 10.1016/j. ad.2015.01.009. In summary, in the presence of a gradually enlarging, blue-purple, hard nodule with homogeneity on dermoscopy, there should be a high index of suspicion for an aneurysmal dermatofibroma. The dermoscopic pattern which may include fine white lines may be identical to some nodular melanomas, however the slow growth and long term evolution indicates its benign nature. These tumors require histological confirmation. References 1. Gonzalez S, Duarte I. Benign fibrous histiocytoma of the skin. A morphologic study of 290 cases. Pathol Res Pract 1982;174(4):379-91. PMID: 6296802. DOI: 10.1016/S0344- 0338(82)80019-8. 2. McKee PH, Calonje E, Granter SR. Fibrohistiocytic tumors. In: McKee PH, Calonje E, Granter SR, eds. Pathology of the Skin with Clinical Correlations. 3rd ed. Philadelphia: Elsevier Mosby; 2005:1741-1760. 3. Kanitakis J, Carbonnel E, Delmonte S, Livrozet JM, Faure M, Claudy A. Multiple eruptive dermatofibromas in a patient with HIV infection: case report and literature review. J Cutan Pathol 2000;27(1):54-6. PMID: 10660133. DOI: 10.1034/j.1600- 0560.2000.027001054.x. 4. Massone C, Parodi A, Virno G, Rebora A. Multiple eruptive dermatofibromas in patients with systemic lupus erythematosus treated with prednisone. Int J Dermatol 2002;41(5):279-81. PMID: 12100703. DOI: 10.1046/j.1365-4362.2002.01493.x. 5. Yazici AC, Baz K, Ikizoglu G, Koca A, Kokturk A, Apa DD. Fa- milial eruptive dermatofibromas in atopic dermatitis. J Eur Acad Dermatol Venereol 2006;20(1):90-2. PMID: 16405617. DOI: 10.1111/j.1468-3083.2005.01357.x.