The Dermatopathologist - December Quiz

Atypical Fibroxanthoma 

The findings are those of a markedly atypical dermal-based spindle cell neoplasm exhibiting positivity for CD10 without any clear-cut evidence of smooth muscle, melanocytic, or epithelial differentiation. The findings are consistent with an atypical fibroxanthoma, a probable dermal-based mesenchymal neoplasm of myofibroblastic derivation. Despite a worrisome histology, the lesions do not exhibit an aggressive clinical behavior. The differential diagnosis is with a pleomorphic dermal sarcoma that is really the aggressive equivalent of an atypical fibroxanthoma, whereby morphologic features favoring this diagnosis include subcutaneous extension, vascular invasion, and overall size. In this regard, the diagnosis of pleomorphic dermal sarcoma cannot be excluded. 

For quiz 2, go to the next page. 

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Case 2. 

A 60-year-old woman presented with an upper back pink flesh-colored rubbery papule (Figures A-D).

a. Pilar leiomyoma

b. Traumatic neuroma

c. Palisaded encapsulated neuroma

d. Neurofibroma

To learn the answer, go to the next page.

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Case 2 - D

Neurofibroma

Neurofibroma is a benign nerve sheath tumor composed of a mixture of Schwann cells, perineurial cells, and fibroblasts. They can be sporadic or arise in association with neurofibromatosis. Cutaneous lesions are flesh colored, soft, and present as papules or nodules. They constitute the most common type of benign tumor encountered in patients with type I neurofibromatosis. Cutaneous neurofibromas are benign but can be excised for cosmetic purposes.

For quiz 3, go to the next page.

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Case 3.

A 30-year-old man presented with an upper arm vascular nodule (Figures A-D).

a. Hobnail targetoid hemosiderotic hemangioma

b. Kaposi sarcoma

c. Hobnail hemangioendothelioma 

d. Kaposiform hemangioendothelioma

To learn the answer, go to the next page.

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Case 3 - A

Hobnail Targetoid Hemosiderotic Hemangioma 

The findings are those of a benign vasoformative lesion of blood vessel endothelial cell derivation. The morphology in this case is distinctive for a rare benign vascular lesion, namely the hobnail targetoid hemosiderotic hemangioma. It is characterized by a solitary papule on the limbs or trunk of younger and middle-aged people. Some authors prefer the designation of superficial hemosiderotic lymphovascular malformation. Other authors have postulated trauma to lymphatic vessels with the development of lymphatic vascular malformation as being pathogenetically key. Upon examination of the light microscopic findings, there is some degree of scar, extravasation of red cells, hemosiderin deposition, telangiectasia, and lymphectasia. These lesions are quite small with a central violaceous papule surrounded by an eccentric ichthyotic rim resulting in a targetoid appearance. Well-formed dilated vascular spaces with protuberant endothelial are present in the superficial dermis with protruding or hobnailed endothelial cells lining superficial vessels. There is variable hemosiderin and red cell extravasation. The lack of endothelial cell atypia militates against the diagnosis of angiosarcoma.

Dr Magro is the director of dermatopathology at Weill Cornell Medicine in New York, NY. For more information, please visit www.weillcornelldermpath.com.

Disclosure: The author reports no relevant financial relationships.