Balloon cell melanoma: a case report with polarized and non-polarized dermatoscopy and dermatopathology

Abstract

Balloon cell melanoma is a rare melanoma subtype, with only one previous case with dermatoscopy published. It is often non-pigmented, leading to diagnostic difficulty, and there is a tendency for lesions to be thick at diagnosis. We report a case of balloon cell melanoma on the forearm of a 61-year-old man with both polarized and non-polarized dermatoscopy and dermatopathology. It presented as a firm pale nodule with focal eccentric pigmentation. The clinical images evoke a differential diagnosis of dermatofibroma, dermal nevus, Spitz nevus and basal cell carcinoma as well as melanoma. This melanoma was partially pigmented due to a small, pigmented superficial spreading component on the edge of the non-pigmented balloon cell nodule, prompting further evaluation. In retrospect there was the clue to malignancy of polarizing-specific white lines (chrysalis structures) and polymorphous vessels, including a pattern of dot vessels. The reticular lines exclude basal cell carcinoma, polarizing-specific white lines are inconsistent with the diagnosis of dermal nevus and their eccentric location is inconsistent with both Spitz nevus and dermatofibroma. Excision biopsy was performed, revealing a superficial spreading melanoma with two distinct invasive components, one of atypical non-mature epithelioid cells and the other an amelanotic nodular component, comprising more than 50% of the lesion, characterized by markedly distended epithelioid melanocytes showing pseudo-xanthomatous cytoplasmic balloon cell morphology. A diagnosis of balloon cell melanoma, Breslow thickness 1.9 mm, mitotic rate 3 per square millimeter was rendered. Wide local excision was performed, as was sentinel lymph node biopsy, which was negative.

Keywords: balloon cell melanoma; balloon cells; chrysalis structures; dermatopathology; dermatoscopy; dermoscopy.

Figure 1.

Clinical (A) and close up (B) images of a pale nodule on the forearm of a 61-year-old man with skin of Fitzpatrick photo-type 2. There are foci of eccentric pigmentation at the periphery. Three hairs, similar to surrounding hairs, are seen to be emerging from the nodule. [Copyright: ©2014 Maher et al.]

Figure 2.

Polarized dermatoscopy image of the lesion shown in Figure 1. There is a structureless white area with a rim of structureless brown containing focal reticular lines. A focal pattern of dot vessels coincides with a focal pattern of polarizing-specific perpendicular white lines (black arrow). There is another separate focal pattern of dot vessels (red arrow). Elsewhere at the periphery of the structureless white area there are a several linear (curved) vessels. [Copyright: ©2014 Maher et al.]

Figure 3.

Non-polarized dermatoscopy image of the lesion shown in Figure 2. No white lines are seen in this image. [Copyright: ©2014 Maher et al.]

Figure 4.

Low power dermatopathologic overview of the lesion shown in Figures 1–3 with a dominant nodular component comprised exclusively of markedly distended epithelioid melanocytes showing pseudo-xanthomatous cytoplasmic balloon cell morphology. On the right side of the image (black-boxed area) there is a separate invasive component of non-balloon cell malignant melanocytes. The black-boxed area is shown at higher power in Figure 5 and the red-boxed area in Figure 6. [Copyright: ©2014 Maher et al.]

Figure 5.

Medium high power view of the black-boxed area in Figure 4. Atypical melanocytes are confluent at the dermoepidermal junction, and on the right side of the image they are seen as a nested proliferation in the deep papillary dermis including nests in proximity to an eccrine duct. On the left side of the image a separate population of atypical melanocytes with distended balloon cell morphology is apparent. Melanin pigment can be seen at the dermoepidermal junction. [Copyright: ©2014 Maher et al.]

Figure 6.

Medium high power view of the red-boxed area in Figure 4. The melanocytic proliferation at the dermoepidermal junction is only focally confluent and pagetoid spread is sparse and partial-thickness only. There is abundant melanin at the basal layer. Large balloon cells are closely packed in the reticular dermis with an absence of intervening stroma in this part of the lesion. [Copyright: ©2014 Maher et al.]

Figure 7.

High power view of distended, vacuolated balloon cells in the base of the nodule shown in Figure 4. Arrows point to a cell in mitosis. [Copyright: ©2014 Maher et al.]