A solitary auricular polyp.

A 73-year-old man presented to his dermatologist with a 1 cm, polypoid, left auricular lesion of 1-year duration. His past medical history was significant for prostatic adenocarcinoma.

A biopsy was obtained, and immunohistochemical staining for Melan-A was performed [Figures 1 and 2].

Figure 1

(a) Dilated vascular spaces associated with atypical epithelioid cells (H and E, ×20), (b) Nested atypical epithelioid cells within vascular lumen (H and E, ×100)

Figure 2

(a) Epithelioid cells with moderate cytoplasm, visible nucleoli, and focal mitosis (H and E, ×600), (b) Diffuse cytoplasmic staining of the population of interest with Melan-A (red chromogen) (×100)

The most likely diagnosis is:

Congenital pattern nevus with pseudovascular spaces

Epithelioid angiosarcoma

Glomangioma

Metastatic melanoma associated with an angiokeratoma

Lobular capillary hemangioma (pyogenic granuloma).

ANSWER

Metastatic melanoma associated with an angiokeratoma

DISCUSSION

The histological sections demonstrated dilated and focally thrombosed vascular spaces within the superficial dermis. The overlying epidermis showed focal atrophy, but was otherwise unremarkable. Adjacent to and within the vascular lumens, atypical epithelioid cells arranged in nests and sheets were noted, without definitive maturation or dispersion [Figure 1a and b]. Furthermore, conspicuous nucleoli and rare mitoses were appreciated in the epithelioid cell proliferation [Figure 2a]. Immunohistochemical stains for S-100 and Melan-A [Figure 2b] highlighted the tumor.

Albeit rare, published case reports and small series have described the co-occurrence of cutaneous melanoma and other neoplasms (epithelial, mesenchymal, and hematopoietic). Concomitant melanoma and malignant (basal cell carcinoma [BCC], squamous cell carcinoma, chronic lymphocytic leukemia, leiomyosarcoma, Paget's disease, atypical fibroxanthoma, and Merkel cell carcinoma)[1234567] as well as benign tumors (seborrheic keratosis)[8] have been documented with BCC reported most often. To further clarify the confusing terminology used to describe these unique lesions, several authors have proposed a standardized nomenclature with four general subcategories including: combination, collision, biphenotypic, and colonization tumors.[9101112] However, due in large part to the relative paucity of cases, the biology and therefore clinical relevance of these lesions is not well-understood.

In the current case, given the clinical history of a solitary lesion, the possibility of a primary melanoma was considered. However, the absence of an in-situ lesion, focal sheet-like growth with poor maturation in a predominantly intravascular location, and relatively monomorphic atypical cytology of the nevoid/epithelioid population suggest a metastasis. As the distinction between primary cutaneous and metastatic melanoma has significant prognostic and therapeutic implications, criteria incorporating both architectural and cytologic features have been proposed in an attempt to elucidate this quandary.[13] The presence of an intraepidermal (in-situ) and/or benign nevic component, relative absence of lymphovascular invasion, polymorphous cytology, and fewer mitoses favor a primary lesion. In contrast, a dermal and/or subcutaneous infiltrate, extensive lymphovascular invasion, monomorphous population, and numerous mitoses favor a metastasis. Ultimately, however, the correlation of clinical and radiologic findings, as was suggested in our case, is critical in arriving at an accurate diagnosis.